WorldWideScience

Sample records for accelerometers

  1. Piezoelectric Accelerometers Development

    DEFF Research Database (Denmark)

    Liu, Bin; Bang, Lisbet Fogh

    1999-01-01

    The paper describes the development of piezoelectric accelerometers using Finite Element (FE) approach. Brüel & Kjær Accelerometer Type 8325 is chosen as an example to illustrate the advanced accelerometer development procedure. The deviation between simulated results and measured results of Type...

  2. A microchip optomechanical accelerometer

    CERN Document Server

    Krause, Alexander G; Blasius, Tim D; Lin, Qiang; Painter, Oskar

    2012-01-01

    The monitoring of accelerations is essential for a variety of applications ranging from inertial navigation to consumer electronics. The basic operation principle of an accelerometer is to measure the displacement of a flexibly mounted test mass; sensitive displacement measurement can be realized using capacitive, piezo-electric, tunnel-current, or optical methods. While optical readout provides superior displacement resolution and resilience to electromagnetic interference, current optical accelerometers either do not allow for chip-scale integration or require bulky test masses. Here we demonstrate an optomechanical accelerometer that employs ultra-sensitive all-optical displacement read-out using a planar photonic crystal cavity monolithically integrated with a nano-tethered test mass of high mechanical Q-factor. This device architecture allows for full on-chip integration and achieves a broadband acceleration resolution of 10 \\mu g/rt-Hz, a bandwidth greater than 20 kHz, and a dynamic range of 50 dB with ...

  3. Double resonator cantilever accelerometer

    Science.gov (United States)

    Koehler, Dale R.

    1984-01-01

    A digital quartz accelerometer includes a pair of spaced double-ended tuning forks fastened at one end to a base and at the other end through a spacer mass. Transverse movement of the resonator members stresses one and compresses the other, providing a differential frequency output which is indicative of acceleration.

  4. A Simple Accelerometer Calibrator

    Science.gov (United States)

    Salam, R. A.; Islamy, M. R. F.; Munir, M. M.; Latief, H.; Irsyam, M.; Khairurrijal

    2016-08-01

    High possibility of earthquake could lead to the high number of victims caused by it. It also can cause other hazards such as tsunami, landslide, etc. In that case it requires a system that can examine the earthquake occurrence. Some possible system to detect earthquake is by creating a vibration sensor system using accelerometer. However, the output of the system is usually put in the form of acceleration data. Therefore, a calibrator system for accelerometer to sense the vibration is needed. In this study, a simple accelerometer calibrator has been developed using 12 V DC motor, optocoupler, Liquid Crystal Display (LCD) and AVR 328 microcontroller as controller system. The system uses the Pulse Wave Modulation (PWM) form microcontroller to control the motor rotational speed as response to vibration frequency. The frequency of vibration was read by optocoupler and then those data was used as feedback to the system. The results show that the systems could control the rotational speed and the vibration frequencies in accordance with the defined PWM.

  5. Capacitive Position Sensor For Accelerometer

    Science.gov (United States)

    Vanzandt, Thomas R.; Kaiser, William J.; Kenny, Thomas W.

    1995-01-01

    Capacitive position sensor measures displacement of proof mass in prototype accelerometer described in "Single-Crystal Springs for Accelerometers" (NPO-18795). Sensor is ultrasensitive, miniature device operating at ultra-high frequency and described in more detail in "Ultra-High-Frequency Capacitive Displacement Sensor," (NPO-18675). Advances in design and fabrication of prototype accelerometer also applicable to magnetometers and other sensors in which sensed quantities measured in terms of deflections of small springs.

  6. Piezoelectric accelerometers with integral electronics

    CERN Document Server

    Levinzon, Felix

    2014-01-01

    This book provides an invaluable reference to Piezoelectric Accelerometers with Integral Electronics (IEPE). It describes the design and performance parameters of IEPE accelerometers and their key elements, PE transducers and FET-input amplifiers. Coverage includes recently designed, low-noise and high temperature IEPE accelerometers. Readers will benefit from the detailed noise analysis of the IEPE accelerometer, which enables estimation of its noise floor and noise limits. Other topics useful for designers of low-noise, high temperature silicon-based electronics include noise analysis of FET

  7. Optomechanical reference accelerometer

    CERN Document Server

    Gerberding, Oliver; Melcher, John; Pratt, Jon; Taylor, Jacob

    2015-01-01

    We present an optomechanical accelerometer with high dynamic range, high bandwidth and read-out noise levels below 8 {\\mu}g/$\\sqrt{\\mathrm{Hz}}$. The straightforward assembly and low cost of our device make it a prime candidate for on-site reference calibrations and autonomous navigation. We present experimental data taken with a vacuum sealed, portable prototype and deduce the achieved bias stability and scale factor accuracy. Additionally, we present a comprehensive model of the device physics that we use to analyze the fundamental noise sources and accuracy limitations of such devices.

  8. Dual-Cantilever-Beam Accelerometer

    Science.gov (United States)

    Reynolds, Emmitt A.; Speckhart, Frank H.

    1988-01-01

    Sensitivity to velocity changes along beam axis reduced. Weighted-end cantilever beams of accelerometer deflected equally by acceleration in y direction. When acceleration to right as well as up or down, right beam deflected more, while left beam deflected less. Bridge circuit averages outputs of strain gauges measuring deflections, so cross-axis sensitivity of accelerometer reduced. New device simple and inexpensive.

  9. The LISA accelerometer

    Science.gov (United States)

    Rodrigues, M.; Touboul, P.

    2003-10-01

    In the frame of investigating the fundamental nature of gravity, the Laser Interferometer Space Antenna (LISA) mission could open the way to a new kind of observations unreachable from ground. The experiment, based on a V-formation of six drag-free spacecraft, uses the cubic proof masses of inertial sensors to reflect the laser light, acting as reference mirrors of a 5 × 10 9 m arm length interferometer. The proof masses are also used as inertial references for the drag-free control of the spacecraft which constitute in return a shield against external forces. Derived from space electrostatic accelerometers developed at ONERA, such as GRADIO for the ESA ARISTOTELES and now GOCE mission (Bernard and Touboul, 1991), the proposed LISA sensor should shield its proof mass from any accelerometric disturbance at a level of 10 -15ms-2Hz- 1/2. The accurate capacitive sensing of the mass provides its position relative to the satellite with a resolution better than 10 -9m Hz- 1/2 in order to control the satellite orbit and to minimise the disturbances induced by the satellite self gravity or by the proof mass charge. The sensor configuration and accomodation has to be specifically optimised for the mission requirements. Fortunately, the sensor will benefit from the thermal stability of the LISA optical bench environment, i.e. 10 -6K Hz- 1/2, and of the selected materials that exhibit a very low coefficient of thermal expansion (CTE), ensuring a high geometrical stability. Apart from the modeling and the evaluation of the flight characteristics, the necessary indirect ground demonstration of the performance and the interfaces with the drag-free control will have to be considered in detail in the future.

  10. Equating accelerometer estimates among youth

    DEFF Research Database (Denmark)

    Brazendale, Keith; Beets, Michael W; Bornstein, Daniel B;

    2016-01-01

    OBJECTIVES: Different accelerometer cutpoints used by different researchers often yields vastly different estimates of moderate-to-vigorous intensity physical activity (MVPA). This is recognized as cutpoint non-equivalence (CNE), which reduces the ability to accurately compare youth MVPA across s...

  11. Accelerometer for mobile robot positioning

    OpenAIRE

    Liu, HS; Pang, GKH

    1999-01-01

    An evaluation of a low-cost, small sized solid state accelerometer is described in this paper. The sensor is intended for positioning of a mobile robot or platform. The acceleration signal outputted by the sensor is doubly integrated with time which yields the traveled distance. Bias offset drift exhibits in the acceleration signal is accumulative and the accuracy of the distance measurement deteriorates with time due to the integration. A Kalman filter is used to reduce errors caused by rand...

  12. Application of MEMS accelerometer to geophysics

    OpenAIRE

    AIZAWA, Takao; Kimura, Toshinori; Matsuoka, Toshifumi; Takeda, Tetsuya; Asano, Youichi

    2008-01-01

    We developed several types of MEMS accelerometers using commercial MEMS elements for trial use in seismic surveys. Field experiments and earthquake observations were carried out for investigating the capabilities of the MEMS accelerometers. The results of these experiments and observations show that the properties of these MEMS accelerometers are similar and that they are about 1.5-3.0 times as sensitive as conventional geophones used in seismic surveys. The noise level of the MEMS 3-C accele...

  13. Quantifiying the stability of walking using accelerometers

    NARCIS (Netherlands)

    Waarsing, Jan H.; Mayagoitia, Ruth E.; Veltink, Peter H.

    1996-01-01

    A dynamic analysis method is sought to measure the relative stability of walking, using a triaxial accelerometer. A performance parameter that can be calculated from the data from the accelerometer is defined; it should give a measure of the stability of the subject. It is based on the balancing for

  14. High Temperature Endurable Fiber Optic Accelerometer

    Directory of Open Access Journals (Sweden)

    Yeon-Gwan Lee

    2014-01-01

    Full Text Available This paper presents a low frequency fiber optic accelerometer for application in high temperature environments of civil engineering structures. The reflection-based extrinsic fiber optic accelerometer developed in this study consists of a transmissive grating panel, reflective mirror, and two optical fiber collimators as the transceiver whose function can be maintained up to 130°C. The dynamic characteristics of the sensor probe were investigated and the correlation between the natural frequency of the sensor probe and temperature variation was described and discussed. Furthermore, high temperature simulation equipment was designed for the verification test setup of the developed accelerometer for high temperature. This study was limited to consideration of 130°C applied temperature to the proposed fiber optic accelerometer due to an operational temperature limitation of commercial optical fiber collimator. The sinusoidal low frequency accelerations measured from the developed fiber optic accelerometer at 130°C demonstrated good agreement with that of an MEMS accelerometer measured at room temperature. The developed fiber optic accelerometer can be used in frequency ranges below 5.1 Hz up to 130°C with a margin of error that is less than 10% and a high sensitivity of 0.18 (m/s2/rad.

  15. Hybridizing matter-wave and classical accelerometers

    CERN Document Server

    Lautier, Jean; Hardin, Thomas; Merlet, Sebastien; Santos, Franck Pereira Dos; Landragin, Arnaud

    2014-01-01

    We demonstrate a hybrid accelerometer that benefits from the advantages of both conventional and atomic sensors in terms of bandwidth (DC to 430 Hz) and long term stability. First, the use of a real time correction of the atom interferometer phase by the signal from the classical accelerometer enables to run it at best performances without any isolation platform. Second, a servo-lock of the DC component of the conventional sensor output signal by the atomic one realizes a hybrid sensor. This method paves the way for applications in geophysics and in inertial navigation as it overcomes the main limitation of atomic accelerometers, namely the dead times between consecutive measurements.

  16. Hybridizing matter-wave and classical accelerometers

    Science.gov (United States)

    Lautier, J.; Volodimer, L.; Hardin, T.; Merlet, S.; Lours, M.; Pereira Dos Santos, F.; Landragin, A.

    2014-10-01

    We demonstrate a hybrid accelerometer that benefits from the advantages of both conventional and atomic sensors in terms of bandwidth (DC to 430 Hz) and long term stability. First, the use of a real time correction of the atom interferometer phase by the signal from the classical accelerometer enables to run it at best performance without any isolation platform. Second, a servo-lock of the DC component of the conventional sensor output signal by the atomic one realizes a hybrid sensor. This method paves the way for applications in geophysics and in inertial navigation as it overcomes the main limitation of atomic accelerometers, namely, the dead times between consecutive measurements.

  17. Hybridizing matter-wave and classical accelerometers

    Energy Technology Data Exchange (ETDEWEB)

    Lautier, J.; Volodimer, L.; Hardin, T.; Merlet, S.; Lours, M.; Pereira Dos Santos, F.; Landragin, A., E-mail: arnaud.landragin@obspm.fr [LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, 61 avenue de l' Observatoire, 75014 Paris (France)

    2014-10-06

    We demonstrate a hybrid accelerometer that benefits from the advantages of both conventional and atomic sensors in terms of bandwidth (DC to 430 Hz) and long term stability. First, the use of a real time correction of the atom interferometer phase by the signal from the classical accelerometer enables to run it at best performance without any isolation platform. Second, a servo-lock of the DC component of the conventional sensor output signal by the atomic one realizes a hybrid sensor. This method paves the way for applications in geophysics and in inertial navigation as it overcomes the main limitation of atomic accelerometers, namely, the dead times between consecutive measurements.

  18. Accelerometer Measurements in the Amusement Park.

    Science.gov (United States)

    Reno, Charles; Speers, Robert R.

    1995-01-01

    Describes the use of the Texas Instruments' calculator-based laboratory (CBL) and Vernier accelerometer for measuring the vector sum of the gravitational field and the acceleration of amusement park rides. (JRH)

  19. A mechanical model of the smartphone's accelerometer

    CERN Document Server

    Gallitto, Aurelio Agliolo

    2015-01-01

    To increase the attention of students, several physics experiments can be performed at school, as well at home, by using the smartphone as laboratory tools. In the paper we describe a mechanical model of the smartphone's accelerometer, which can be used in classroom to allow students to better understand the principle of the accelerometer even by students at the beginning of the study in physics.

  20. High Temperature Endurable Fiber Optic Accelerometer

    OpenAIRE

    Yeon-Gwan Lee; Jin-Hyuk Kim; Chun-Gon Kim

    2014-01-01

    This paper presents a low frequency fiber optic accelerometer for application in high temperature environments of civil engineering structures. The reflection-based extrinsic fiber optic accelerometer developed in this study consists of a transmissive grating panel, reflective mirror, and two optical fiber collimators as the transceiver whose function can be maintained up to 130°C. The dynamic characteristics of the sensor probe were investigated and the correlation between the natural freque...

  1. The Development of Piezoelectric Accelerometers Using Finite Element Analysis

    DEFF Research Database (Denmark)

    Liu, Bin

    1999-01-01

    This paper describes the application of Finite Element (FE) approach for the development of piezoelectric accelerometers. An accelerometer is simulated using the FE approach as an example. Good agreement is achieved between simulated results and calibrated results. It is proved that the FE modeli...... can be effectively used to predict the specifications of the accelerometer, especially when modification of the accelerometer is required. The FE developing technology forms the bases of fast responsiveness and flexible customized design of piezoelectric accelerometers....

  2. The Development of Piezoelectric Accelerometers Using Finite Elemen Analysis

    DEFF Research Database (Denmark)

    Liu, Bin; Yao, Q.; Kriegbaum, B.

    1999-01-01

    This paper describes the application of Finite Element (FE) approach for the development of piezoelectric accelerometers. An accelerometer is simulated using the FE approach as an example. Good agreement is achieved between simulated results and calibrated results. It is proved that the FE modeli...... can be effectively used to predict the specifications of the accelerometer, especially when modification of the accelerometer is required. The FE developing technology forms the bases of fast responsiveness and flexible customized design of piezoelectric accelerometers...

  3. Accelerometers for Precise GNSS Orbit Determination

    Science.gov (United States)

    Hugentobler, Urs; Schlicht, Anja

    2016-07-01

    The solar radiation pressure is the largest non-gravitational acceleration on GNSS satellites limiting the accuracy of precise orbit models. Other non-gravitational accelerations may be thrusts for station keeping maneuvers. Accelerometers measure the motion of a test mass that is shielded against satellite surface forces with respect to a cage that is rigidly connected to the satellite. They can thus be used to measure these difficult-to-model non-gravitational accelerations. Accelerometers however typically show correlated noise as well as a drift of the scaling factors converting measured voltages to accelerations. The scaling thus needs to be regularly calibrated. The presented study is based on several simulated scenarios including orbit determination of accelerometer-equipped Galileo satellites. It shall evaluate different options on how to accommodate accelerometer measurements in the orbit integrator, indicate to what extent currently available accelerometers can be used to improve the modeling of non-gravitational accelerations on GNSS satellites for precise orbit determination, and assess the necessary requirements for an accelerometer that can serve this purpose.

  4. Detecting gunshots using wearable accelerometers.

    Science.gov (United States)

    Loeffler, Charles E

    2014-01-01

    Gun violence continues to be a staggering and seemingly intractable issue in many communities. The prevalence of gun violence among the sub-population of individuals under court-ordered community supervision provides an opportunity for intervention using remote monitoring technology. Existing monitoring systems rely heavily on location-based monitoring methods, which have incomplete geographic coverage and do not provide information on illegal firearm use. This paper presents the first results demonstrating the feasibility of using wearable inertial sensors to recognize wrist movements and other signals corresponding to firearm usage. Data were collected from accelerometers worn on the wrists of subjects shooting a number of different firearms, conducting routine daily activities, and participating in activities and tasks that could be potentially confused with firearm discharges. A training sample was used to construct a combined detector and classifier for individual gunshots, which achieved a classification accuracy of 99.4 percent when tested against a hold-out sample of observations. These results suggest the feasibility of using inexpensive wearable sensors to detect firearm discharges.

  5. Detecting gunshots using wearable accelerometers.

    Directory of Open Access Journals (Sweden)

    Charles E Loeffler

    Full Text Available Gun violence continues to be a staggering and seemingly intractable issue in many communities. The prevalence of gun violence among the sub-population of individuals under court-ordered community supervision provides an opportunity for intervention using remote monitoring technology. Existing monitoring systems rely heavily on location-based monitoring methods, which have incomplete geographic coverage and do not provide information on illegal firearm use. This paper presents the first results demonstrating the feasibility of using wearable inertial sensors to recognize wrist movements and other signals corresponding to firearm usage. Data were collected from accelerometers worn on the wrists of subjects shooting a number of different firearms, conducting routine daily activities, and participating in activities and tasks that could be potentially confused with firearm discharges. A training sample was used to construct a combined detector and classifier for individual gunshots, which achieved a classification accuracy of 99.4 percent when tested against a hold-out sample of observations. These results suggest the feasibility of using inexpensive wearable sensors to detect firearm discharges.

  6. Optomechanical accelerometers and gravity gradiometers

    Science.gov (United States)

    Guzman, Felipe

    2016-04-01

    Compact optical cavities can be combined with highly stable mechanical oscillators to yield accelerometers and gravity gradiometers of exquisite sensitivity, which are also traceable to the SI. We have incorporated Fabry-Pérot fiber-optic micro-cavities onto low-loss monolithic fused-silica mechanical oscillators for gradiometry, acceleration, and force sensing. These devices consist solely of a glass oscillator and fiber optics to inject and read out the coherent optical signal, making them very simple and compatible with space applications. We have demonstrated displacement sensitivities better than 200 am/√Hz with these fiber-optic micro-sensors. This translates into broadband acceleration noise floors below 100 nano-g/√Hz over a 10kHz, when combined with compact high frequency mechanical oscillators. Similarly, we have developed monolithic oscillators with resonance frequencies near and below 10 Hz, yielding measurement sensitivities better than 10‑9 m/s2. We will introduce our sensor concepts and present results on our fiber-optic displacement sensors and novel optomechanical devices.

  7. VARIOMETRIC TESTS FOR ACCELEROMETER SENSORS

    Directory of Open Access Journals (Sweden)

    M. G. D'Urso

    2012-08-01

    Full Text Available We present a comprehensive review of several variometric tests recently carried out on a home-made measurement system composed of a tern of low-cost accelerometer sensors of MEMS (Micro-Electro-Mechanical Systems type equipped with autonomous electric supply and wireless transmission. The most important parameters characterizing the systematic errors, i.e. bias, scale factor and thermal correction factor, have been evaluated by calibration tests based upon the so-called "six -positions" static test proposed by the IEEE 517 Standard. In this way the system optimal configuration has been defined in terms of data acquisition frequency and of scale factor. In addition to such tests, partly documented elsewhere, the results of some sensitivity tests on the influence of external environmental factors are also presented. With the aim of employing the proposed MEMS-based system as a device for monitoring the onset of slope landslides, some further tests have been carried out in order to measure the inclination of rigid objects which the sensors have been fixed to. The most significant results of the tests are illustrated and discussed.

  8. ISA accelerometer and Moon science

    Science.gov (United States)

    Iafolla, Valerio; Peron, Roberto; Santoli, Francesco; Fiorenza, Emiliano; Lefevre, Carlo; Nozzoli, Sergio; Reale, Andrea

    2010-05-01

    In recent years the Moon has become again a target for exploration activities, as shown by many performed, ongoing or foreseen missions. The reason for this new wave are manifold. The knowledge of formation and evolution of the Moon to current state is important in order to trace the overall history of Solar System. An effective driving factor is the possibility of building a human settlement on its surface, with all the related issues of environment characterization, safety, resources, communication and navigation. Our natural satellite is also an important laboratory for fundamental physics: Lunar Laser Ranging is continuing to provide important data that constrain possible theories of gravitation. All these topics are providing stimulus and inspirations for new experiments. ISA (Italian Spring Accelerometer) can provide an important tool for lunar studies. Thanks to its structure (three one-dimensional sensors assembled in a composite structure) it works both in-orbit and on-ground, with the same configuration. It therefore can be used onboard a spacecraft, as a support to a radio science mission, and on the surface of the Moon, as a seismometer. The first option has been explorated in the context of MAGIA (Missione Altimetrica Gravimetrica geochImica lunAre), a proposal for an exploration mission with a noteworthy part dedicated to gravimetry and fundamental physics. The second option is candidate to be hosted on NASA ILN (International Lunar Network) and ESA First Lunar Lander. After a description of the instrument, both of them will be described and discussed, giving emphasis on the integration of the instrument with the other components of the respective experiments.

  9. High performance MEMS accelerometers for concrete SHM applications and comparison with COTS accelerometers

    Science.gov (United States)

    Kavitha, S.; Joseph Daniel, R.; Sumangala, K.

    2016-01-01

    Accelerometers used for civil and huge mechanical structural health monitoring intend to measure the shift in the natural frequency of the monitored structures (noise floor. Sensitivity of accelerometers is inversely proportional to the frequency squared. Commercial MEMS (Micro Electro-Mechanical System) accelerometers that are generally designed for large bandwidth (e.g 25 kHz in ADXL150) have poor sensor level sensitivity and therefore uses complex signal conditioning electronics to achieve large sensitivity and low noise floor which in turn results in higher cost. In this work, an attempt has been made to design MEMS capacitive and piezoresistive accelerometers for smaller bandwidth using IntelliSuite and CoventorWare MEMS tools respectively. The various performance metrics have been obtained using simulation experiments and the results show that these sensors have excellent voltage sensitivity, noise performance and high resolution at sensor level and are even superior to commercial MEMS accelerometers.

  10. Fiber optic accelerometer for pipeline surveillance

    Energy Technology Data Exchange (ETDEWEB)

    Valente, Luiz C.G.; Cabral, Bruno S. [LUPATECH Monitoring Systems, Caxias do Sul, RS (Brazil); Braga, Arthur M.B. [Pontificia Universidade Catolica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Mecanica

    2009-07-01

    The use of accelerometers for monitoring vibration due to impacts and other sources associated with pipeline operation is not new, but conventional electric accelerometers present practical problems to be deployed in the field. In this paper we evaluate the use of both commercially available and prototypes of new optical fiber accelerometers for this application. They all share the possibility of operating at long distances from the reading unit. All tests were performed at CTDUT facilities on free pipes as well as on a 14 pol-OD, 100 meters long pipeline loop. Using controlled impacts, several aspects of the application have been analyzed such as different ways of fixing the accelerometers to the pipeline wall, influence of barriers between impact and sensor, and signal propagation through buried sections of pipeline. Results of measurements performed during the operation of the loop are also presented. They include passing PIGs, pumping water out from the system, and working on the tubes to open the loop. Results indicate that the accelerometers can be placed at distances measuring hundreds of meters from the source of vibration, and that the difference in time and frequency behavior of signals measured by sensors placed in different locations along the pipeline may be used to locate and identify that source. (author)

  11. Unbiased acceleration measurements with an electrostatic accelerometer

    CERN Document Server

    Lenoir, Benjamin; Reynaud, Serge

    2011-01-01

    The Gravity Advanced Packaged is an instrument composed of an electrostatic accelerometer MicroSTAR and a rotating stage aiming at measuring with no bias the spacecraft non-gravitational acceleration to test gravitation during interplanetary missions. To do so, the accelerometer is rotated such that post-processing allows separating the signal from the bias. Given the characteristic of MicroSTAR, it is possible to reach a precision of 1 pm.s$^{-2}$ on the acceleration for an integration time of three hours.

  12. Finite Element Based Design and Optimization for Piezoelectric Accelerometers

    DEFF Research Database (Denmark)

    Liu, Bin; Kriegbaum, B.; Yao, Q.

    1998-01-01

    A systematic Finite Element design and optimisation procedure is implemented for the development of piezoelectric accelerometers. Most of the specifications of accelerometers can be obtained using the Finite Element simulations. The deviations between the simulated and calibrated sensitivities...

  13. Piezoelectric Accelerometers Modification Based on the Finite Element Method

    DEFF Research Database (Denmark)

    Liu, Bin; Kriegbaum, B.

    2000-01-01

    The paper describes the modification of piezoelectric accelerometers using a Finite Element (FE) method. Brüel & Kjær Accelerometer Type 8325 is chosen as an example to illustrate the advanced accelerometer development procedure. The deviation between the measurement and FE simulation results...

  14. Dual Accelerometer Usage Strategy for Onboard Space Navigation

    Science.gov (United States)

    Zanetti, Renato; D'Souza, Chris

    2012-01-01

    This work introduces a dual accelerometer usage strategy for onboard space navigation. In the proposed algorithm the accelerometer is used to propagate the state when its value exceeds a threshold and it is used to estimate its errors otherwise. Numerical examples and comparison to other accelerometer usage schemes are presented to validate the proposed approach.

  15. Smartphone MEMS accelerometers and earthquake early warning

    Science.gov (United States)

    Kong, Q.; Allen, R. M.; Schreier, L.; Kwon, Y. W.

    2015-12-01

    The low cost MEMS accelerometers in the smartphones are attracting more and more attentions from the science community due to the vast number and potential applications in various areas. We are using the accelerometers inside the smartphones to detect the earthquakes. We did shake table tests to show these accelerometers are also suitable to record large shakings caused by earthquakes. We developed an android app - MyShake, which can even distinguish earthquake movements from daily human activities from the recordings recorded by the accelerometers in personal smartphones and upload trigger information/waveform to our server for further analysis. The data from these smartphones forms a unique datasets for seismological applications, such as earthquake early warning. In this talk I will layout the method we used to recognize earthquake-like movement from single smartphone, and the overview of the whole system that harness the information from a network of smartphones for rapid earthquake detection. This type of system can be easily deployed and scaled up around the global and provides additional insights of the earthquake hazards.

  16. Fabrication and characterization of a piezoelectric accelerometer

    DEFF Research Database (Denmark)

    Reus, Roger De; Gulløv, Jens; Scheeper, Patrick

    1999-01-01

    Zinc oxide based piezoelectric accelerometers were fabricated by bulk micromachining. A high yield was obtained in a relatively simple process sequence. For two electrode configurations a direction selectivity better than 100 was obtained for acceleration in the vertical direction and a selectivity...

  17. Dark Matter Direct Detection with Accelerometers

    CERN Document Server

    Graham, Peter W; Mardon, Jeremy; Rajendran, Surjeet; Terrano, William A

    2015-01-01

    The mass of the dark matter particle is unknown, and may be as low as ~$10^{-22}$ eV. The lighter part of this range, below ~eV, is relatively unexplored both theoretically and experimentally but contains an array of natural dark matter candidates. An example is the relaxion, a light boson predicted by cosmological solutions to the hierarchy problem. One of the few generic signals such light dark matter can produce is a time-oscillating, EP-violating force. We propose searches for this using accelerometers, and consider in detail the examples of torsion balances, atom interferometry, and pulsar timing. These approaches have the potential to probe large parts of unexplored parameter space in the next several years. Thus such accelerometers provide radically new avenues for the direct detection of dark matter.

  18. Developing accelerometer based on graphene nanoribbon resonators

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jeong Won, E-mail: jwkang@ut.ac.kr [Department of Computer Engineering, Korea National University of Transportation, Chungju 380-702 (Korea, Republic of); Lee, Jun Ha, E-mail: junha@smu.ac.kr [Department of Computer System Engineering, Sangmyung University, Chonan 330-720 (Korea, Republic of); Hwang, Ho Jung, E-mail: hjhwang@cau.ac.kr [School of Electrical and Electronic Engineering, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Kim, Ki-Sub, E-mail: kks1114@ut.ac.kr [Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380-702 (Korea, Republic of)

    2012-10-01

    We investigated an ultrahigh sensitive accelerometer based on graphene nanoribbon resonators. Sensing acceleration can be made by their resonance frequency shift and/or their capacitance change. Schematics and the static properties were introduced and the dynamic properties were investigated via classical molecular dynamics simulation. As the acceleration increased, the oscillations of the deflections were going dramatically faster and the mean deflections increased, then the capacitance continually varied with large amplitudes and the resonance frequencies linearly increased in a log–log scale by power regression. The energy loss decreased with increasing time, and the average quality factors were dramatically reduced with increasing acceleration. -- Highlights: ► Ultrahigh sensitive accelerometer based on graphene nanoribbon resonators. ► Sensing acceleration by resonance frequency shift and/or capacitance change. ► Resonance frequencies linearly increased with increasing acceleration in a log–log scale. ► Quality factors were dramatically reduced with increasing acceleration.

  19. Multi-Axis Accelerometer Calibration System

    Science.gov (United States)

    Finley, Tom; Parker, Peter

    2010-01-01

    A low-cost, portable, and simplified system has been developed that is suitable for in-situ calibration and/or evaluation of multi-axis inertial measurement instruments. This system overcomes facility restrictions and maintains or improves the calibration quality for users of accelerometer-based instruments with applications in avionics, experimental wind tunnel research, and force balance calibration applications. The apparatus quickly and easily positions a multi-axis accelerometer system into a precisely known orientation suitable for in-situ quality checks and calibration. In addition, the system incorporates powerful and sophisticated statistical methods, known as response surface methodology and statistical quality control. These methods improve calibration quality, reduce calibration time, and allow for increased calibration frequency, which enables the monitoring of instrument stability over time.

  20. MGRA: Motion Gesture Recognition via Accelerometer.

    Science.gov (United States)

    Hong, Feng; You, Shujuan; Wei, Meiyu; Zhang, Yongtuo; Guo, Zhongwen

    2016-01-01

    Accelerometers have been widely embedded in most current mobile devices, enabling easy and intuitive operations. This paper proposes a Motion Gesture Recognition system (MGRA) based on accelerometer data only, which is entirely implemented on mobile devices and can provide users with real-time interactions. A robust and unique feature set is enumerated through the time domain, the frequency domain and singular value decomposition analysis using our motion gesture set containing 11,110 traces. The best feature vector for classification is selected, taking both static and mobile scenarios into consideration. MGRA exploits support vector machine as the classifier with the best feature vector. Evaluations confirm that MGRA can accommodate a broad set of gesture variations within each class, including execution time, amplitude and non-gestural movement. Extensive evaluations confirm that MGRA achieves higher accuracy under both static and mobile scenarios and costs less computation time and energy on an LG Nexus 5 than previous methods. PMID:27089336

  1. MGRA: Motion Gesture Recognition via Accelerometer

    Directory of Open Access Journals (Sweden)

    Feng Hong

    2016-04-01

    Full Text Available Accelerometers have been widely embedded in most current mobile devices, enabling easy and intuitive operations. This paper proposes a Motion Gesture Recognition system (MGRA based on accelerometer data only, which is entirely implemented on mobile devices and can provide users with real-time interactions. A robust and unique feature set is enumerated through the time domain, the frequency domain and singular value decomposition analysis using our motion gesture set containing 11,110 traces. The best feature vector for classification is selected, taking both static and mobile scenarios into consideration. MGRA exploits support vector machine as the classifier with the best feature vector. Evaluations confirm that MGRA can accommodate a broad set of gesture variations within each class, including execution time, amplitude and non-gestural movement. Extensive evaluations confirm that MGRA achieves higher accuracy under both static and mobile scenarios and costs less computation time and energy on an LG Nexus 5 than previous methods.

  2. Accurate Telescope Mount Positioning with MEMS Accelerometers

    CERN Document Server

    Mészáros, László; Pál, András; Csépány, Gergely

    2014-01-01

    This paper describes the advantages and challenges of applying microelectromechanical accelerometer systems (MEMS accelerometers) in order to attain precise, accurate and stateless positioning of telescope mounts. This provides a completely independent method from other forms of electronic, optical, mechanical or magnetic feedback or real-time astrometry. Our goal is to reach the sub-arcminute range which is well smaller than the field-of-view of conventional imaging telescope systems. Here we present how this sub-arcminute accuracy can be achieved with very cheap MEMS sensors and we also detail how our procedures can be extended in order to attain even finer measurements. In addition, our paper discusses how can a complete system design be implemented in order to be a part of a telescope control system.

  3. Physics Education using a Smartphone Accelerometer

    CERN Document Server

    Peters, Randall D

    2010-01-01

    Described is an experiment in which a smartphone was caused to move at steady state in a vertical plane, on a path that was nearly circular. During a time interval of data acquisition that encompassed multiple orbits, the acceleration of the phone was measured by means of its internal accelerometer. A subsequent analysis of the data that was collected shows reasonable agreement between experiment and a simple theory of the motion.

  4. The GRADIO accelerometer - Design and development status

    Science.gov (United States)

    Bernard, A.; Touboul, P.

    The concept of Satellite Gravity Gradiometry based on differential microaccelerometry has been proposed by ONERA in the early eighties. Since 1986, an important effort is devoted to the development of the GRADIO accelerometers. Their configuration has been optimized for the ARISTOTELES mission with the objective of 0.01 Eotvos resolution for an integrating time of 4 s. The achieved resolution, better than 10 exp -9 G, is limited by the actual stability of alignments on the testing equipment.

  5. Review: Fifty Years Plus of Accelerometer History for Shock and Vibration (1940–1996

    Directory of Open Access Journals (Sweden)

    Patrick L. Walter

    1999-01-01

    Full Text Available This article summarizes the history of accelerometer development and the subsequent evolution of the commercial accelerometer industry. The focus is primarily on piezoelectric and piezoresistive accelerometers, although early resistance-bridge-type accelerometers are also described. The pioneer accelerometer manufacturing companies are identified and a chronology of technology development through today is presented.

  6. Performance of an Accelerometer Suspended by a Pendulum

    Institute of Scientific and Technical Information of China (English)

    高尚伟; 栾恩杰; 周泽兵; 罗俊

    2003-01-01

    Performances of an accelerometer suspended by a pendulum and set on ground directly are both discussed.Theoretical analysis shows that the isolation from seismic disturbances of such a suspending accelerometer is equal to that of a narrow band-pass electronic filter. This means that the effect of seismic noises to the accelerometer can be substantially suppressed by means of a pendulum suspension during its performance tests.

  7. Design and Implementation of a Micromechanical Silicon Resonant Accelerometer

    Directory of Open Access Journals (Sweden)

    Libin Huang

    2013-11-01

    Full Text Available The micromechanical silicon resonant accelerometer has attracted considerable attention in the research and development of high-precision MEMS accelerometers because of its output of quasi-digital signals, high sensitivity, high resolution, wide dynamic range, anti-interference capacity and good stability. Because of the mismatching thermal expansion coefficients of silicon and glass, the micromechanical silicon resonant accelerometer based on the Silicon on Glass (SOG technique is deeply affected by the temperature during the fabrication, packaging and use processes. The thermal stress caused by temperature changes directly affects the frequency output of the accelerometer. Based on the working principle of the micromechanical resonant accelerometer, a special accelerometer structure that reduces the temperature influence on the accelerometer is designed. The accelerometer can greatly reduce the thermal stress caused by high temperatures in the process of fabrication and packaging. Currently, the closed-loop drive circuit is devised based on a phase-locked loop. The unloaded resonant frequencies of the prototype of the micromechanical silicon resonant accelerometer are approximately 31.4 kHz and 31.5 kHz. The scale factor is 66.24003 Hz/g. The scale factor stability is 14.886 ppm, the scale factor repeatability is 23 ppm, the bias stability is 23 μg, the bias repeatability is 170 μg, and the bias temperature coefficient is 0.0734 Hz/°C.

  8. A three-axis ultrasensitive accelerometer for space

    Science.gov (United States)

    Bernard, A.

    A three-axis ultrasensitive accelerometer ASTRE (Accelerometre Spatial Triaxial Electrostatique) is a simplified version of the GRADIO accelerometer designed for the ARISTOTELES mission, which operates by measuring the force provided by a three-axis electrostatic suspension of the proof-mass. It covers the g-spectrum from 10 exp -8 to 10 exp -4 in the frequency range dc to 5 Hz. A dedicated test bench was developed in order to preserve the accelerometer from the seismic noise. The paper presents the performance parameters of the ASTRE accelerometer and some of the design schemes.

  9. Study of Piezoresistive Micro Electro-Mechanical Accelerometer Design Platform

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    According to the inland micro electro-mechanical system (MEMS) process technique level, a design platform of piezoresistive micro electro-mechanical accelerometer is given. This platform is much more adaptable to the inland designer compared with the current MEMS CAD software. The design flow is presented in detail, and the key techique in the platform is analyzed amply. The structure design methodology is exemplified in the design of a piezoresistive accelerometer, and the accelerometer is the optimized structure for the given performance requirements. The accelerometer is now being manufactured.

  10. Suitability of MEMS Accelerometers for Condition Monitoring: An experimental study

    Directory of Open Access Journals (Sweden)

    Robert Pietruszkiewicz

    2008-02-01

    Full Text Available With increasing demands for wireless sensing nodes for assets control and condition monitoring; needs for alternatives to expensive conventional accelerometers in vibration measurements have been arisen. Micro-Electro Mechanical Systems (MEMS accelerometer is one of the available options. The performances of three of the MEMS accelerometers from different manufacturers are investigated in this paper and compared to a well calibrated commercial accelerometer used as a reference for MEMS sensors performance evaluation. Tests were performed on a real CNC machine in a typical industrial environmental workshop and the achieved results are presented.

  11. Analysis of MEMS Accelerometer for Optimized Sensitivity

    Directory of Open Access Journals (Sweden)

    Khairun Nisa Khamil

    2014-12-01

    Full Text Available Sensitivity is an important element of a sensing process, and it is part of the open-loop gain of the sensor. This makes it a strong inverse relationship between sensitivity and bandwidth for any class of sensors. The geometrical of the accelerometer, mass width, beam (length and width of the device and its sensitivity are analyzed theoretically and also using finite element analysis software, COMSOL Multiphysics®. Hence, the optimization analysis concluded that desired sensitivity can be achieved by adding number of fingers and adjusting the length of the beam. Preliminary results show that the sensitivity of the device increases by significantly by 38%.

  12. The GRADIO accelerometer: Design and development status

    Science.gov (United States)

    Bernard, Alain; Touboul, M. P.

    1991-12-01

    The concept of Satellite Gravity Gradiometry (SGG) based on differential microaccelerometry as proposed in the early eighties is summarized. Work devoted to the development of the GRADIO accelerometers is described. The configuration was optimized for the Aristoteles mission with the objective of increasing resolution for an integrating time of 4 s. Thanks to the selected three axis configuration, very sensitive differential tests were carried out between two very representative laboratory models, in directions perpendicular to gravity. The resolution of these tests, limited by the actual stability of alignments of the testing equipment is described.

  13. Studying and Modeling Vibration Transducers and Accelerometers

    Directory of Open Access Journals (Sweden)

    Katalin Ágoston

    2010-12-01

    Full Text Available This paper presents types and operating mode of vibration sensors. Piezoelectric sensing elements are often used in accelerometers. It will be investigate the structure and transfer function of the seismic mass type sensing element. The article presents how the piezoelectric sensing element works and how can be modeled with an electronic circuit. The transfer functions of the electronic circuit models are studied in Matlab and the results are presented. It will be presented the influence of the seismic mass on the accelerometer’s working frequency domain.

  14. Classification of Sporting Activities Using Smartphone Accelerometers

    Directory of Open Access Journals (Sweden)

    Noel E. O'Connor

    2013-04-01

    Full Text Available In this paper we present a framework that allows for the automatic identification of sporting activities using commonly available smartphones. We extract discriminative informational features from smartphone accelerometers using the Discrete Wavelet Transform (DWT. Despite the poor quality of their accelerometers, smartphones were used as capture devices due to their prevalence in today’s society. Successful classification on this basis potentially makes the technology accessible to both elite and non-elite athletes. Extracted features are used to train different categories of classifiers. No one classifier family has a reportable direct advantage in activity classification problems to date; thus we examine classifiers from each of the most widely used classifier families. We investigate three classification approaches; a commonly used SVM-based approach, an optimized classification model and a fusion of classifiers. We also investigate the effect of changing several of the DWT input parameters, including mother wavelets, window lengths and DWT decomposition levels. During the course of this work we created a challenging sports activity analysis dataset, comprised of soccer and field-hockey activities. The average maximum F-measure accuracy of 87% was achieved using a fusion of classifiers, which was 6% better than a single classifier model and 23% better than a standard SVM approach.

  15. Calibrating Accelerometers Using an Electromagnetic Launcher

    Energy Technology Data Exchange (ETDEWEB)

    Erik Timpson

    2012-05-13

    A Pulse Forming Network (PFN), Helical Electromagnetic Launcher (HEML), Command Module (CM), and Calibration Table (CT) were built and evaluated for the combined ability to calibrate an accelerometer. The PFN has a maximum stored energy of 19.25 kJ bank and is fired by a silicon controlled rectifier (SCR), with appropriate safety precautions. The HEML is constructed out of G-10 fiberglass and is designed to accelerate 600 grams to 10 meters per second. The CM is microcontroller based running Arduino Software. The CM has a keypad input and 7 segment outputs of the bank voltage and desired voltage. After entering a desired bank voltage, the CM controls the charge of the PFN. When the two voltages are equal it allows the fire button to send a pulse to the SCR to fire the PFN and in turn, the HEML. The HEML projectile's tip hits a target that is held by the CT. The CT consists of a table to hold the PFN and HEML, a vacuum chuck, air bearing, velocity meter and catch pot. The Target is held with the vacuum chuck awaiting impact. After impact, the air bearing allows the target to fall freely for the velocity meter to get an accurate reading. A known acceleration is determined from the known change in velocity of the target. Thus, if an accelerometer was attached to the target, the measured value can be compared to the known value.

  16. MEMS Accelerometer with Screen Printed Piezoelectric Thick Film

    DEFF Research Database (Denmark)

    Hindrichsen, Christian Carstensen; Lau-Moeller, R.; Bove, T.;

    2006-01-01

    A bulk-micromachined piezoelectric MEMS accelerometer with screen printed piezoelectric Pb(ZrxTil )O3(PZT) thick film (TF) as the sensing material has been fabricated and characterized. The accelerometer has a four beam structure with a central seismic mass (3600x3600x500 pm3) and a total chip size...

  17. SOI Digital Accelerometer Based on Pull-in Time Configuration

    NARCIS (Netherlands)

    Pakula, L.S.; Rajaraman, V.; French, P.J.

    2009-01-01

    The operation principle, design, fabrication and measurement results of a quasi digital accelerometer fabricated on a thin silicon-on-insulator (SOI) substrate is presented. The accelerometer features quasi-digital output, therefore eliminating the need for analogue signal conditioning. The accelero

  18. High sensitivity optical waveguide accelerometer based on Fano resonance.

    Science.gov (United States)

    Wan, Fenghua; Qian, Guang; Li, Ruozhou; Tang, Jie; Zhang, Tong

    2016-08-20

    An optical waveguide accelerometer based on tunable asymmetrical Fano resonance in a ring-resonator-coupled Mach-Zehnder interferometer (MZI) is proposed and analyzed. A Fano resonance accelerometer has a relatively large workspace of coupling coefficients with high sensitivity, which has potential application in inertial navigation, missile guidance, and attitude control of satellites. Due to the interference between a high-Q resonance pathway and a coherent background pathway, a steep asymmetric line shape is generated, which greatly improves the sensitivity of this accelerometer. The sensitivity of the accelerometer is about 111.75 mW/g. A 393-fold increase in sensitivity is achieved compared with a conventional MZI accelerometer and is approximately equal to the single ring structure. PMID:27556984

  19. Quantitative Accelerated Life Testing of MEMS Accelerometers

    Directory of Open Access Journals (Sweden)

    Jean-Paul Collette

    2007-11-01

    Full Text Available Quantitative Accelerated Life Testing (QALT is a solution for assessing thereliability of Micro Electro Mechanical Systems (MEMS. A procedure for QALT is shownin this paper and an attempt to assess the reliability level for a batch of MEMSaccelerometers is reported. The testing plan is application-driven and contains combinedtests: thermal (high temperature and mechanical stress. Two variants of mechanical stressare used: vibration (at a fixed frequency and tilting. Original equipment for testing at tiltingand high temperature is used. Tilting is appropriate as application-driven stress, because thetilt movement is a natural environment for devices used for automotive and aerospaceapplications. Also, tilting is used by MEMS accelerometers for anti-theft systems. The testresults demonstrated the excellent reliability of the studied devices, the failure rate in the“worst case” being smaller than 10-7h-1.

  20. A high performance, variable capacitance accelerometer

    Science.gov (United States)

    Wilner, L. Bruce

    1988-12-01

    A variable capacitance acceleration sensor is described. Manufactured using silicon microfabrication techniques, the sensor uses a midplane, flat plate suspension, gas damping, and overrange stops. The sensor is assembled from three silicon wafers, using anodic bonds to inlays of borosilicate glass. Typical sensor properties are 7-pF active capacitance, 3-pF tare capacitance, a response of 0.05 pF/G, a resonance frequency of 3.4 kHz, and damping 0.7 critical. It is concluded that this sensor, with appropriate electronics, forms an accelerometer with an order-of-magnitude greater sensitivity-bandwidth product than a comparable piezoresistive acclerometer, and with extraordinary shock resistance.

  1. Self Diagnostic Accelerometer Testing on the C-17 Aircraft

    Science.gov (United States)

    Tokars, Roger P.; Lekki, John D.

    2013-01-01

    The self diagnostic accelerometer (SDA) developed by the NASA Glenn Research Center was tested for the first time in an aircraft engine environment as part of the Vehicle Integrated Propulsion Research (VIPR) program. The VIPR program includes testing multiple critical flight sensor technologies. One such sensor, the accelerometer, measures vibrations to detect faults in the engine. In order to rely upon the accelerometer, the health of the accelerometer must be ensured. The SDA is a sensor system designed to actively determine the accelerometer structural health and attachment condition, in addition to vibration measurements. The SDA uses a signal conditioning unit that sends an electrical chirp to the accelerometer and recognizes changes in the response due to changes in the accelerometer health and attachment condition. To demonstrate the SDAs flight worthiness and robustness, multiple SDAs were mounted and tested on a C-17 aircraft engine. The engine test conditions varied from engine off, to idle, to maximum power. The SDA attachment conditions were varied from fully tight to loose. The newly developed SDA health algorithm described herein uses cross correlation pattern recognition to discriminate a healthy from a faulty SDA. The VIPR test results demonstrate for the first.

  2. Vibration sensing in smart machine rotors using internal MEMS accelerometers

    Science.gov (United States)

    Jiménez, Samuel; Cole, Matthew O. T.; Keogh, Patrick S.

    2016-09-01

    This paper presents a novel topology for enhanced vibration sensing in which wireless MEMS accelerometers embedded within a hollow rotor measure vibration in a synchronously rotating frame of reference. Theoretical relations between rotor-embedded accelerometer signals and the vibration of the rotor in an inertial reference frame are derived. It is thereby shown that functionality as a virtual stator-mounted displacement transducer can be achieved through appropriate signal processing. Experimental tests on a prototype rotor confirm that both magnitude and phase information of synchronous vibration can be measured directly without additional stator-mounted key-phasor sensors. Displacement amplitudes calculated from accelerometer signals will become erroneous at low rotational speeds due to accelerometer zero-g offsets, hence a corrective procedure is introduced. Impact tests are also undertaken to examine the ability of the internal accelerometers to measure transient vibration. A further capability is demonstrated, whereby the accelerometer signals are used to measure rotational speed of the rotor by analysing the signal component due to gravity. The study highlights the extended functionality afforded by internal accelerometers and demonstrates the feasibility of internal sensor topologies, which can provide improved observability of rotor vibration at externally inaccessible rotor locations.

  3. Type of development and application of integrating accelerometer

    Science.gov (United States)

    Pan, Hongxia; Li, Ting; Liu, Guangpu; Yu, Hongying

    2000-05-01

    In this paper a new technique is suggested to solve the problem of measuring the vibration parameters in bad conditions with strong shock, that is, using integrating accelerometers repacked with normal inertial accelerometers to measure vibration acceleration signal of rocket launcher and then integrating velocity and displacement parameters. After the problems of integral accuracy have been solved, various vibration parameters are obtained to meet the needs of a certain project. By analysis, this integrating accelerometer has been testified to be a very practical sensor with surplus value in measuring vibration parameters in bad condition with strong shock.

  4. Adaptive integrated navigation filtering based on accelerometer calibration

    Directory of Open Access Journals (Sweden)

    Qifan Zhou

    2012-11-01

    Full Text Available In this paper, a novel GPS (Global Positioning System and DR (Dead Reckoning system which was based on the accelerometer and gyroscope integrated system was designed and implemented. In this system, the odometer used in traditional DR system was replaced by a MEMS tri-axis accelerometer in order to decrease the cost and the volume of the system. The system was integrated by the Kalman filter and a new mathematical model was introduced. In order to reasonably use the GPS information, an adaptive algorithm based on single measurement system which could estimate the measurement noise covariance was obtained. On the purpose of reducing the effect of the accumulated error caused by drift and bias of accelerometer, the accelerometer was calibrated online when GPS performed well. In this way, the integrated system could not only obtain the high-precision positioning in real time, but also perform stably in practice.

  5. A Novel Frequency Output Accelerometer Using Ring Oscillator and Mixer

    Institute of Scientific and Technical Information of China (English)

    ZHANGZhaohua; YUERuifeng; LIULitian

    2004-01-01

    A novel digital accelerometer using ring oscillator and mixer is presented. The sensitive unit of this accelerometer is MOS ring oscillators located on silicon beams. The output is frequency signal. Mixer is used as interior signal processor in order to improve characteristics of the output signal. The accelerometer has many perfect characteristics such as high sensitivity, low temperature coefficient and simple fabrication process. The frequency character of MOS ring oscillator and its relationship with acceleration are described. The MOS ring oscillator, mixer circuits and physical structures of this accelerometer are designed. The device was fabricated by standard IC process mixed with MEMS process. The sensitivity of fabricated devices is 6.91 kHz/g.

  6. Predicting human movement with multiple accelerometers using movelets

    DEFF Research Database (Denmark)

    He, Bing; Bai, Jiawei; Zipunnikov, Vadim V;

    2014-01-01

    PURPOSE: The study aims were 1) to develop transparent algorithms that use short segments of training data for predicting activity types and 2) to compare the prediction performance of the proposed algorithms using single accelerometers and multiple accelerometers. METHODS: Sixteen participants...... developed, which, instead of extracting features, build activity-specific dictionaries composed of short signal segments called movelets. Three alternative approaches were proposed to integrate the information from the multiple accelerometers. RESULTS: With at most several seconds of training data per...... activity, the prediction accuracy at the second-level temporal resolution was very high for lying, standing, normal/fast walking, and standing up from a chair (the median prediction accuracy ranged from 88.2% to 99.9% on the basis of the single-accelerometer movelet approach). For these activities, wrist...

  7. Estimating energy expenditure during front crawl swimming using accelerometers

    DEFF Research Database (Denmark)

    Nordsborg, Nikolai Baastrup; Espinosa, Hugo G.; Van Thiel, David H

    2014-01-01

    The determination of energy expenditure is of major interest in training load and performance assessment. Small, wireless accelerometer units have the potential to characterise energy expenditure during swimming. The correlation between absorbed oxygen versus flume swimming speed and absorbed oxy...

  8. High sensitivity accelerometers for high performance seismic attenuators

    International Nuclear Information System (INIS)

    We present concepts and features of a new horizontal accelerometer whose mechanical design and machining process aim to improve the sensitivity in the frequency region between 10 mHz and 1 Hz. The expected sensitivity, less than 10-11 m/s2/√(Hz) around 100 mHz, is a couple of orders of magnitude below the state of art limits. This accelerometer could be integrated in the active control of the LIGO II mirror seismic isolators

  9. Input-output stability for accelerometer control systems

    Science.gov (United States)

    Banks, H. T.; Morris, K. A.

    1991-01-01

    It is shown that, although accelerometer control systems are not well-posed in the sense of Salamon, a well-defined input-output relation exists. It is established that the output of an accelerometer control system can be described by the convolution of the input and a distribution. This distribution is Laplace transformable, and the Laplace transform of the distribution is the transfer function of the system.

  10. Intelligent seismic sensor with double three component MEMS accelerometers

    Science.gov (United States)

    Fu, Jihua; Wang, Jianjun; Li, Zhitao; Liu, Xiaoxi; Wang, Zhongyu

    2010-08-01

    To better understand the response and damage characteristics of structures under earthquakes, a great number of intelligent seismic sensors with high performance were needed to be installed distributed in the whole country. The intelligent seismic sensor was a cost-sensitive application because of its large number of usages. For this reason, a low cost intelligent seismic sensor was put forward in this paper. This kind of intelligent seismic sensor cut down the cost without sacrificing performance by introducing two three component MEMS accelerometers. It was composed by a microprocessor, two three component MEMS accelerometers, an A/D converter, a flash memory, etc. The MEMS accelerometer has better structure and frequency response characteristics than the conventional geophones'. But one MEMS accelerometer tended to be unreliable and have no enough dynamic range for precision measurement. Therefore two three component MEMS accelerometers were symmetrically mounted on both sides of the circuit board. And their measuring values were composed to describe the ground motion or structure response. The composed value was the in-phase stacking of the two accelerometers' measuring values, which enhanced the signal noise ratio of the sensor and broadened its dynamic range. Through the preliminary theory and experiment analysis, the low cost intelligent seismic sensor could measure the acceleration in accuracy.

  11. Isolation of a piezoresistive accelerometer used in high acceleration tests

    Science.gov (United States)

    Bateman, V. I.; Brown, F. A.; Davie, N. T.

    Both uniaxial and triaxial shock isolation techniques for a piezoresistive accelerometer have been developed for pyroshock and impact tests. The uniaxial shock isolation technique has demonstrated acceptable characteristics for a temperature range of -50 to +186 F and a frequency bandwidth of DC to 10 kHz. The triaxial shock isolation technique has demonstrated acceptable results for a temperature range of -50 to 70 F and a frequency bandwidth of DC to 10 kHz. These temperature ranges, that are beyond the accelerometer manufacturer's operational limits of -30 and +150 F, required the calibration of accelerometers at high shock levels and at the temperature extremes of -50 and +160 F. The purposes of these calibrations were to insure that the accelerometers operated at the field test temperatures and to provide an accelerometer sensitivity at each test temperature. Since there is no NIST-traceable (National Institute of Standards and Technology traceable) calibration capability at shock levels of 5,000 - 15,000 g for the temperature extremes of -50 and +160 F, a method for calibrating and certifying the Hopkinson bar with a transfer standard was developed. Time domain and frequency domain results are given that characterize the Hopkinson bar. The NIST-traceable accuracy for the standard accelerometer in shock is +\\-5%. The Hopkinson bar has been certified by the Sandia Secondary Standards Division with an uncertainty of 6%.

  12. Quantitative evaluation of gait ataxia by accelerometers.

    Science.gov (United States)

    Shirai, Shinichi; Yabe, Ichiro; Matsushima, Masaaki; Ito, Yoichi M; Yoneyama, Mitsuru; Sasaki, Hidenao

    2015-11-15

    An appropriate biomarker for spinocerebellar degeneration (SCD) has not been identified. Here, we performed gait analysis on patients with pure cerebellar type SCD and assessed whether the obtained data could be used as a neurophysiological biomarker for cerebellar ataxia. We analyzed 25 SCD patients, 25 patients with Parkinson's disease as a disease control, and 25 healthy control individuals. Acceleration signals during 6 min of walking and 1 min of standing were measured by two sets of triaxial accelerometers that were secured with a fixation vest to the middle of the lower and upper back of each subject. We extracted two gait parameters, the average and the coefficient of variation of motion trajectory amplitude, from each acceleration component. Then, each component was analyzed by correlation with the Scale for the Assessment and Rating of Ataxia (SARA) and the Berg Balance Scale (BBS). Compared with the gait control of healthy subjects and concerning correlation with severity and disease specificity, our results suggest that the average amplitude of medial-lateral (upper back) of straight gait is a physiological biomarker for cerebellar ataxia. Our results suggest that gait analysis is a quantitative and concise evaluation scale for the severity of cerebellar ataxia.

  13. Strong Motion Seismograph Based On MEMS Accelerometer

    Science.gov (United States)

    Teng, Y.; Hu, X.

    2013-12-01

    The MEMS strong motion seismograph we developed used the modularization method to design its software and hardware.It can fit various needs in different application situation.The hardware of the instrument is composed of a MEMS accelerometer,a control processor system,a data-storage system,a wired real-time data transmission system by IP network,a wireless data transmission module by 3G broadband,a GPS calibration module and power supply system with a large-volumn lithium battery in it. Among it,the seismograph's sensor adopted a three-axis with 14-bit high resolution and digital output MEMS accelerometer.Its noise level just reach about 99μg/√Hz and ×2g to ×8g dynamically selectable full-scale.Its output data rates from 1.56Hz to 800Hz. Its maximum current consumption is merely 165μA,and the device is so small that it is available in a 3mm×3mm×1mm QFN package. Furthermore,there is access to both low pass filtered data as well as high pass filtered data,which minimizes the data analysis required for earthquake signal detection. So,the data post-processing can be simplified. Controlling process system adopts a 32-bit low power consumption embedded ARM9 processor-S3C2440 and is based on the Linux operation system.The processor's operating clock at 400MHz.The controlling system's main memory is a 64MB SDRAM with a 256MB flash-memory.Besides,an external high-capacity SD card data memory can be easily added.So the system can meet the requirements for data acquisition,data processing,data transmission,data storage,and so on. Both wired and wireless network can satisfy remote real-time monitoring, data transmission,system maintenance,status monitoring or updating software.Linux was embedded and multi-layer designed conception was used.The code, including sensor hardware driver,the data acquisition,earthquake setting out and so on,was written on medium layer.The hardware driver consist of IIC-Bus interface driver, IO driver and asynchronous notification driver. The

  14. Relative performance of several inexpensive accelerometers

    Science.gov (United States)

    Evans, John R.; Rogers, John A.

    1995-01-01

    We examined the performance of several low-cost accelerometers for highly cost-driven applications in recording earthquake strong motion. We anticipate applications for such sensors in providing the lifeline and emergency-response communities with an immediate, comprehensive picture of the extent and characteristics of likely damage. We also foresee their use as 'filler' instruments sited between research-grade instruments to provide spatially detailed and near-field records of large earthquakes (on the order of 1000 stations at 600-m intervals in San Fernando Valley, population 1.2 million, for example). The latter applications would provide greatly improved attenuation relationships for building codes and design, the first examples of mainshock information (that is, potentially nonlinear regime) for microzonation, and a suite of records for structural engineers. We also foresee possible applications in monitoring structural inter-story drift during earthquakes, possibly leading to local and remote alarm functions as well as design criteria. This effort appears to be the first of its type at the USGS. It is spurred by rapid advances in sensor technology and the recognition of potential non-classical applications. In this report, we estimate sensor noise spectra, relative transfer functions and cross-axis sensitivity of six inexpensive sensors. We tested three micromachined ('silicon-chip') sensors in addition to classical force-balance and piezoelectric examples. This sample of devices is meant to be representative, not comprehensive. Sensor noise spectra were estimated by recording system output with the sensor mounted on a pneumatically supported 545-kg optical-bench isolation table. This isolation table appears to limit ground motion to below our system noise level. These noise estimates include noise introduced by signal-conditioning circuitry, the analog-to-digital converter (ADC), and noise induced in connecting wiring by ambient electromagnetic fields in

  15. One testing method of dynamic linearity of an accelerometer

    Science.gov (United States)

    Lei, Jing-Yu; Guo, Wei-Guo; Tan, Xue-Ming; Shi, Yun-Bo

    2015-09-01

    To effectively test dynamic linearity of an accelerometer over a wide rang of 104 g to about 20 × 104g, one published patent technology is first experimentally verified and analysed, and its deficient is presented, then based on stress wave propagation theory on the thin long bar, the relation between the strain signal and the corresponding acceleration signal is obtained, one special link of two coaxial projectile is developed. These two coaxial metal cylinders (inner cylinder and circular tube) are used as projectiles, to prevent their mutual slip inside the gun barrel during movement, the one end of two projectiles is always fastened by small screws. Ti6-AL4-V bar with diameter of 30 mm is used to propagate loading stress pulse. The resultant compression wave can be measured by the strain gauges on the bar, and a half -sine strain pulse is obtained. The measuring accelerometer is attached on the other end of the bar by a vacuum clamp. In this clamp, the accelerometer only bear compression wave, the reflected tension pulse make the accelerometer off the bar. Using this system, dynamic linearity measurement of accelerometer can be easily tested in wider range of acceleration values. And a really measuring results are presented.

  16. Prediction of Gap Asymmetry in Differential Micro Accelerometers

    Directory of Open Access Journals (Sweden)

    Xiaoping He

    2012-05-01

    Full Text Available Gap asymmetry in differential capacitors is the primary source of the zero bias output of force-balanced micro accelerometers. It is also used to evaluate the applicability of differential structures in MEMS manufacturing. Therefore, determining the asymmetry level has considerable significance for the design of MEMS devices. This paper proposes an experimental-theoretical method for predicting gap asymmetry in differential sensing capacitors of micro accelerometers. The method involves three processes: first, bi-directional measurement, which can sharply reduce the influence of the feedback circuit on bias output, is proposed. Experiments are then carried out on a centrifuge to obtain the input and output data of an accelerometer. Second, the analytical input-output relationship of the accelerometer with gap asymmetry and circuit error is theoretically derived. Finally, the prediction methodology combines the measurement results and analytical derivation to identify the asymmetric error of 30 accelerometers fabricated by DRIE. Results indicate that the level of asymmetry induced by fabrication uncertainty is about ±5 × 10−2, and that the absolute error is about ±0.2 µm under a 4 µm gap.

  17. Italian spring accelerometer (ISA) a high sensitive accelerometer for ``BepiColombo'' ESA CORNERSTONE

    Science.gov (United States)

    Iafolla, V.; Nozzoli, S.

    2001-12-01

    The targets of the ESA CORNERSTONE mission to Mercury "BepiColombo" are concerned with both planetary and magnetospheric physics and to test some aspects of the general relativity. A payload devoted to a set of experiments named radio science is located within one of the three proposed modules, the Mercury Planetary Orbiter (MPO). In particular, a high sensitivity accelerometer ( a minFisica dello Spazio Interplanetario (IFSI), with the financial support of the Agenzia Spaziale Italiana (ASI). A prototype of such an instrument was constructed, matching the requirements of the radio science experiment. Results of the study concerning the use of ISA in the BepiColombo mission are reported here, particular care being devoted to the description of the instrument and to its sensitivity and thermal stabilisation.

  18. An Electromagnetically Excited Silicon Nitride Beam Resonant Accelerometer

    Directory of Open Access Journals (Sweden)

    2009-02-01

    Full Text Available A resonant microbeam accelerometer of a novel highly symmetric structure based on MEMS bulk-silicon technology is proposed and some numerical modeling results for this scheme are presented. The accelerometer consists of two proof masses, four supporting hinges, two anchors, and a vibrating triple beam, which is clamped at both ends to the two proof masses. LPCVD silicon rich nitride is chosen as the resonant triple beam material, and parameter optimization of the triple-beam structure has been performed. The triple beam is excited and sensed electromagnetically by film electrodes located on the upper surface of the beam. Both simulation and experimental results show that the novel structure increases the scale factor of the resonant accelerometer, and ameliorates other performance issues such as cross axis sensitivity of insensitive input acceleration, etc.

  19. Optical accelerometer design based on laser self-mixing interference

    Science.gov (United States)

    Yang, Ying; Li, Xingfei; Kou, Ke; Zhang, Limin

    2015-03-01

    A novel optical accelerometer based on laser self-mixing effect is presented and experimentally demonstrated, which consists of a mass-loaded elastic-beam assembly and laser self-mixing interferometer. Under external acceleration, an inertial force is applied to the mass, flexible beams deflect from their equilibrium position. The deflection can be read out by the self-mixing interferometer. In order to reduce the impact of higher harmonic, wavelet analysis is introduced to remove singular points. Preliminary results indicate that the resolution is 0.19μg/Hz1/2 within a bandwidth of 100Hz. The optical accelerometer has the potential to achieve high-precision, compact accelerometers.

  20. Physical activity in adolescents – Accelerometer data reduction criteria

    DEFF Research Database (Denmark)

    Toftager, Mette; Breum, Lars; Kristensen, Peter Lund;

    Introduction: Accelerometry is increasingly being recognized as an accurate and reliable method to assess free-living physical activity (PA). However, reporting of accelerometer data reduction and methods remains inconsistent. In this study we investigated the impact of different data reduction...... criteria on participant inclusion and PA data outcomes. Methods: We used data from the Danish SPACE for physical activity study (n=1,348,11–13y). Adolescents wore the Actigraph GT3X for seven consecutive days. Accelerometer data were analyzed using a range of values for three key data reduction issues...... and PA outcomes (mean cpm). The following parameters in the data reduction analyses were fixed: 30sec epoch, 24h duration, first registration accepted after 4h, maximum value 20,000cpm, and two activity epochs permitted in blocks of non-wear. Results: Accelerometer data were obtained from a total of 1...

  1. Adapting MCM-D technology to a piezoresistive accelerometer packaging

    Science.gov (United States)

    Collado, A.; Plaza, J. A.; Cabruja, E.; Esteve, J.

    2003-07-01

    A silicon-on-silicon multichip module for a piezoresistive accelerometer is presented in this paper. This packaging technology, a type of wafer level packaging, offers fully complementary metal-oxide semiconductor compatible silicon substrates, so a pre-amplification stage can be included at substrate level. The electrical contacts and a partial sealing of the sensor mobile structures are performed at the same step using flip-chip technology, so the cost is reduced. As accelerometers are stress-sensitive devices, great care must be taken in the fabrication process and materials. Thus, test structures have been included to study the packaging effects. In this paper we report on the compatibility of accelerometer and wafer level packaging technologies.

  2. Micromachined force-balance feedback accelerometer with optical displacement detection

    Science.gov (United States)

    Nielson, Gregory N.; Langlois, Eric; Baker, Michael; Okandan, Murat; Anderson, Robert

    2014-07-22

    An accelerometer includes a proof mass and a frame that are formed in a handle layer of a silicon-on-an-insulator (SOI). The proof mass is separated from the frame by a back-side trench that defines a boundary of the proof mass. The accelerometer also includes a reflector coupled to a top surface of the proof mass. An optical detector is located above the reflector at the device side. The accelerometer further includes at least one suspension spring. The suspension spring has a handle anchor that extends downwards from the device side to the handle layer to mechanically support upward and downward movement of the proof mass relative to a top surface of the proof mass.

  3. Extracting Time-Accurate Acceleration Vectors From Nontrivial Accelerometer Arrangements.

    Science.gov (United States)

    Franck, Jennifer A; Blume, Janet; Crisco, Joseph J; Franck, Christian

    2015-09-01

    Sports-related concussions are of significant concern in many impact sports, and their detection relies on accurate measurements of the head kinematics during impact. Among the most prevalent recording technologies are videography, and more recently, the use of single-axis accelerometers mounted in a helmet, such as the HIT system. Successful extraction of the linear and angular impact accelerations depends on an accurate analysis methodology governed by the equations of motion. Current algorithms are able to estimate the magnitude of acceleration and hit location, but make assumptions about the hit orientation and are often limited in the position and/or orientation of the accelerometers. The newly formulated algorithm presented in this manuscript accurately extracts the full linear and rotational acceleration vectors from a broad arrangement of six single-axis accelerometers directly from the governing set of kinematic equations. The new formulation linearizes the nonlinear centripetal acceleration term with a finite-difference approximation and provides a fast and accurate solution for all six components of acceleration over long time periods (>250 ms). The approximation of the nonlinear centripetal acceleration term provides an accurate computation of the rotational velocity as a function of time and allows for reconstruction of a multiple-impact signal. Furthermore, the algorithm determines the impact location and orientation and can distinguish between glancing, high rotational velocity impacts, or direct impacts through the center of mass. Results are shown for ten simulated impact locations on a headform geometry computed with three different accelerometer configurations in varying degrees of signal noise. Since the algorithm does not require simplifications of the actual impacted geometry, the impact vector, or a specific arrangement of accelerometer orientations, it can be easily applied to many impact investigations in which accurate kinematics need to

  4. Isolation of a piezoresistive accelerometer used in high acceleration tests

    Energy Technology Data Exchange (ETDEWEB)

    Bateman, V.I.; Brown, F.A.; Davie, N.T.

    1992-12-31

    Both uniaxial and triaxial shock isolation techniques for a piezoresistive accelerometer have been developed for pyroshock and impact tests. The uniaxial shock isolation technique has demonstrated acceptable characteristics for a temperature range of {minus}50{degree}F to +186{degree}F and a frequency bandwidth of DC to 10 kHz. The triaxial shock isolation technique has demonstrated acceptable results for a temperature range of {minus}50{degree}F to 70{degree}F and a frequency bandwidth of DC to 10 kHz. These temperature ranges, that are beyond the accelerometer manufacturer`s operational limits of {minus}30{degree}F and +150{degree}F, required the calibration of accelerometers at high shock levels and at the temperature extremes of {minus}50{degree}F and +160{degree}F. The purposes of these calibrations were to insure that the accelerometers operated at the field test temperatures and to provide an accelerometer sensitivity at each test temperature. Since there is no NIST-traceable (National Institute of Standards and Technology traceable) calibration capability at shock levels of 5,000 g - 15,000 g for the temperature extremes of {minus}50{degree}F and +160{degree}F, a method for calibrating and certifying the Hopkinson bar with a transfer standard was developed. Time domain and frequency domain results are given that characterize the Hopkinson bar. The NIST-traceable accuracy for the standard accelerometer in shock is {plus_minus}5%. The Hopkinson bar has been certified by the Sandia Secondary Standards Division with an uncertainty of 6%.

  5. Improved Signal Processing Technique Leads to More Robust Self Diagnostic Accelerometer System

    Science.gov (United States)

    Tokars, Roger; Lekki, John; Jaros, Dave; Riggs, Terrence; Evans, Kenneth P.

    2010-01-01

    The self diagnostic accelerometer (SDA) is a sensor system designed to actively monitor the health of an accelerometer. In this case an accelerometer is considered healthy if it can be determined that it is operating correctly and its measurements may be relied upon. The SDA system accomplishes this by actively monitoring the accelerometer for a variety of failure conditions including accelerometer structural damage, an electrical open circuit, and most importantly accelerometer detachment. In recent testing of the SDA system in emulated engine operating conditions it has been found that a more robust signal processing technique was necessary. An improved accelerometer diagnostic technique and test results of the SDA system utilizing this technique are presented here. Furthermore, the real time, autonomous capability of the SDA system to concurrently compensate for effects from real operating conditions such as temperature changes and mechanical noise, while monitoring the condition of the accelerometer health and attachment, will be demonstrated.

  6. Fabrication of a Miniaturized ZnO Nanowire Accelerometer and Its Performance Tests

    Directory of Open Access Journals (Sweden)

    Hyun Chan Kim

    2016-09-01

    Full Text Available This paper reports a miniaturized piezoelectric accelerometer suitable for a small haptic actuator array. The accelerometer is made with zinc oxide (ZnO nanowire (NW grown on a copper wafer by a hydrothermal process. The size of the accelerometer is 1.5 × 1.5 mm2, thus fitting the 1.8 × 1.8 mm2 haptic actuator array cell. The detailed fabrication process of the miniaturized accelerometer is illustrated. Performance evaluation of the fabricated accelerometer is conducted by comparing it with a commercial piezoelectric accelerometer. The output current of the fabricated accelerometer increases linearly with the acceleration. The miniaturized ZnO NW accelerometer is feasible for acceleration measurement of small and lightweight devices.

  7. Fiber-optical accelerometers based on polymer optical fiber Bragg gratings

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Stefani, Alessio; Bang, Ole;

    2010-01-01

    Fiber-optical accelerometers based on polymer optical fiber Bragg gratings (FBGs) are reported. We have written 3mm FBGs for 1550nm operation, characterized their temperature and strain response, and tested their performance in a prototype accelerometer.......Fiber-optical accelerometers based on polymer optical fiber Bragg gratings (FBGs) are reported. We have written 3mm FBGs for 1550nm operation, characterized their temperature and strain response, and tested their performance in a prototype accelerometer....

  8. Design and Evaluation of Accelerometer based Motional Feedback

    DEFF Research Database (Denmark)

    Schneider, Henrik; Pranjic, Emilio; Agerkvist, Finn T.;

    2015-01-01

    and enable radical design changes in the loudspeaker which can lead to efficiency improvements. In combination this has motivated a revisit of the accelerometer based motional feedback technique. Experimental results on a 8 inch subwoofer show that the total harmonic distortion can be significantly reduced...

  9. High Sensitivity Polymer Optical Fiber-Bragg-Grating-Based Accelerometer

    DEFF Research Database (Denmark)

    Stefani, Alessio; Andresen, Søren; Yuan, Wu;

    2012-01-01

    We report on the fabrication and characterization of the first accelerometer based on a polymer optical fiber Bragg grating (FBG) for operation at both 850 and 1550 nm. The devices have a flat frequency response over a 1-kHz bandwidth and a resonance frequency of about 3 kHz. The response is line...

  10. Systematic characterisation of silicon-embedded accelerometers for mechanomyography.

    Science.gov (United States)

    Silva, J; Chau, T; Naumann, S; Heim, W

    2003-05-01

    Silicon soft suction sockets (roll-on sleeves) currently used in passive prostheses for below-elbow amputees could also be used in externally powered prostheses, enhancing their functionality and comfort. However, as it is extremely difficult to hold currently used electromyography (EMG) sensors in place reliably within a silicon socket, an alternative measurement of muscular activity as the control input is necessary. Mechanomyography (MMG) is the epidermal measurement of the low-frequency vibrations produced by a contracting muscle. MMG sensors do not have to be in direct contact with the skin. Moreover, the embedding of sensors in the roll-on sleeve may also solve attachment issues, making sensor placement flexible. Therefore the objective was to determine the feasibility of recording MMG signals using silicon-embedded, micro-machined accelerometers. Fifteen embedded accelerometers were excited with predefined vibration patterns. The signal-to-noise ratio (SNR) and frequency response of each sample were measured and compared with those of non-embedded accelerometers. The SNR of embedded samples (approximately equal to 19 dB) was significantly higher than that of non-embedded samples (approximately equal to 12 dB), owing to the considerable mechanical damping effect of the silicon in the 300-900 Hz bandwidth (p=0.0028). This has implications for the application of silicon-embedded accelerometers for externally powered prosthesis control. PMID:12803293

  11. Diurnal Cycles of Tree Mass Obtained Using Accelerometers

    Science.gov (United States)

    Llamas, R. A.; Niemeier, J. J.; Kruger, A.; Lintz, H. E.; Kleinknecht, G. J.; Miller, R. A.

    2013-12-01

    We used a non-invasive technique to estimate the mass of trees using accelerometers. The technique was inspired by Selker et al., 2011 who performed experiments with an oak tree to estimate the time-varying canopy mass. The technique consists of placing an accelerometer on the trunk of a live tree. The resonance frequency is related to the mass of the tree. Wind drives the tree and the accelerometer data are analyzed to obtain estimates of the resonance frequency and mass of the tree. In addition to wind speed and direction, we also collected ambient temperature and rain accumulation using co-located instruments. We collected data for 3 months using several accelerometers configured for different sampling rates. Analysis of the data revealed diurnal cycles in temperature, wind speed, and tree mass derived from the tree resonance frequency. We used the Welch method for power spectral density estimation to obtain hourly estimates of the tree resonance frequency. Our hypothesis is that the mass diurnal cycle is related to the tree water content.

  12. Joint angle estimation with accelerometers for dynamic postural analysis.

    Science.gov (United States)

    Ma, Jianting; Kharboutly, Haissam; Benali, Abderraouf; Benamar, Faïz; Bouzit, Mourad

    2015-10-15

    This paper presents a new accelerometer based method for estimating the posture of a subject standing on a dynamic perturbation platform. The induced perturbation is used to study the control mechanisms as well as the balance requirements that regulate the upright standing. These perturbations are translated into different intensity levels of speed and acceleration along longitudinal and lateral directions of motion. In our method, the human posture is modeled by a tridimensional, three-segment inverted pendulum which simultaneously takes into account both the anterior-posterior and medio-lateral strategies of hip and ankle. Four tri-axial accelerometers are used her, one accelerometer is placed on the platform, and the other three are attached to a human subject. Based on the results, the joint angle estimated compare closely to measurements from magnetic encoders placed on an articulated arm joint. The results were also comparable to those found when using a high-end optical motion capture system coupled with advanced biomechanical simulation software. This paper presents the comparisons of our accelerometer-based method with encoder and optical marker based method of the estimated joint angles under different dynamics perturbations. PMID:26338097

  13. GPS-Based Reduced Dynamic Orbit Determination Using Accelerometer Data

    Science.gov (United States)

    VanHelleputte, Tom; Visser, Pieter

    2007-01-01

    Currently two gravity field satellite missions, CHAMP and GRACE, are equipped with high sensitivity electrostatic accelerometers, measuring the non-conservative forces acting on the spacecraft in three orthogonal directions. During the gravity field recovery these measurements help to separate gravitational and non-gravitational contributions in the observed orbit perturbations. For precise orbit determination purposes all these missions have a dual-frequency GPS receiver on board. The reduced dynamic technique combines the dense and accurate GPS observations with physical models of the forces acting on the spacecraft, complemented by empirical accelerations, which are stochastic parameters adjusted in the orbit determination process. When the spacecraft carries an accelerometer, these measured accelerations can be used to replace the models of the non-conservative forces, such as air drag and solar radiation pressure. This approach is implemented in a batch least-squares estimator of the GPS High Precision Orbit Determination Software Tools (GHOST), developed at DLR/GSOC and DEOS. It is extensively tested with data of the CHAMP and GRACE satellites. As accelerometer observations typically can be affected by an unknown scale factor and bias in each measurement direction, they require calibration during processing. Therefore the estimated state vector is augmented with six parameters: a scale and bias factor for the three axes. In order to converge efficiently to a good solution, reasonable a priori values for the bias factor are necessary. These are calculated by combining the mean value of the accelerometer observations with the mean value of the non-conservative force models and empirical accelerations, estimated when using these models. When replacing the non-conservative force models with accelerometer observations and still estimating empirical accelerations, a good orbit precision is achieved. 100 days of GRACE B data processing results in a mean orbit fit of

  14. The MICROSTAR electrostatic accelerometer for the GRASP Mission

    Science.gov (United States)

    Foulon, Bernard; Christophe, Bruno; Liorzou, Francoise; Huynh, Phuong-Anh; Perrot, Eddy

    2015-04-01

    The Geodetic Reference Antenna in Space (GRASP) is a micro satellite mission concept dedicated to the enhancement of all the space geodetic techniques, and promising revolutionary improvements to the definition of the Terrestrial Reference Frame (TRF). GRASP collocates GPS, SLR, VLBI, and DORIS sensors on a dedicated spacecraft in order to establish precise and stable ties between the key geodetic techniques used to define and disseminate the TRF. GRASP also offers a space-based reference antenna for the present and future Global Navigation Satellite Systems (GNSS). The integration of an ultra sensitive accelerometer at the Center of mass of the satellite can provide not only improvement of the Precise Orbit Determination (POD) by the accurate measurement of the non-gravitational force acting on the surface of the satellite but also by the possibility to calibrate with an accuracy better than 100 µm the change in the position of the Satellite Center of Mass as it is performed in the GRACE mission and to determine the precise motion of the antennas assuming some rigid structure between them and the accelerometer as it is done between the star sensor, the optical cube assembly of satellite laser ranging system and the accelerometer in the GRACE-Follow On mission. The proposed accelerometer is miniaturized version of the electrostatic accelerometers developed for the Earth gravity missions CHAMP, GRACE, GOCE and GRACE-FO. He has 3 sensitive axes thanks to a cubic proof-mass and provides the 3 linear accelerations and the 3 angular accelerations about its 3 orthogonal axes. He is called MICROSTAR and its foreseen performance is a linear acceleration noise lower than 10-11 ms-2/Hz1/2 into a measurement bandwidth between 10-3 Hz and 0.1 Hz.

  15. Design of MEMS accelerometer based acceleration measurement system for automobiles

    Science.gov (United States)

    Venkatesh, K. Arun; Mathivanan, N.

    2012-10-01

    Design of an acceleration measurement system using a MEMS accelerometer to measure acceleration of automobiles in all the three axes is presented. Electronic stability control and anti-lock breaking systems in automobiles use the acceleration measurements to offer safety in driving. The system uses an ARM microcontroller to quantize the outputs of accelerometer and save the measurement data on a microSD card. A LabVIEW program has been developed to analyze the longitudinal acceleration measurement data and test the measurement system. Random noises generated and added with measurement data during measurement are filtered by a Kalman filter implemented in LabVIEW. Longitudinal velocity of the vehicle is computed from the measurement data and displayed on a graphical chart. Typical measurement of velocity of a vehicle at different accelerations and decelerations is presented.

  16. An Improved Wavelet Correction for Zero Shifted Accelerometer Data

    Directory of Open Access Journals (Sweden)

    Timothy S. Edwards

    2003-01-01

    Full Text Available Accelerometer data from shock measurements often contains a spurious DC drifting phenomenon known as zero shifting. This erroneous signal can be caused by a variety of sources. The most conservative approach when dealing with such data is to discard it and collect a different set with steps taken to prevent the zero shifting. This approach is rarely practical, however. The test article may have been destroyed or it may be impossible or prohibitively costly to recreate the test. A method has been proposed by which wavelets may be used to correct the acceleration data. By comparing the corrected accelerometer data to an independent measurement of the acceleration from a laser vibrometer this paper shows that the corrected data, in the cases presented, accurately represents the shock. A method is presented by which the analyst may accurately choose the wavelet correction parameters. The comparisons are made in the time and frequency domains, as well as with the shock response spectrum.

  17. Geometric anti-spring vertical accelerometers for seismic monitoring

    International Nuclear Information System (INIS)

    A new low-frequency, very-low noise, vertical accelerometer is presented. The sensor has been designed to be part of an array of few hundred such devices to be used to predict local gravity fluctuations. These fluctuations, acting on the mirrors of gravitational wave interferometers, are a fundamental source of noise that can only be subtracted from the recorded signal. The motion of a 36 g mass supported by loaded springs is monitored by a high-resolution capacitance sensor; a feedback force actuator keeps the mass in the equilibrium position. The feedback signal is proportional to the acceleration in the frequency range 0-150 Hz. The accelerometer spectral sensitivity is better than 10-9 m/√Hz in the same band, with a dynamic range exceeding 150 dB

  18. Guidelines for Standardized Testing of Broadband Seismometers and Accelerometers

    Science.gov (United States)

    Hutt, Charles R.; Evans, John R.; Followill, Fred; Nigbor, Robert L.; Wielandt, Erhard

    2010-01-01

    Testing and specification of seismic and earthquake-engineering sensors and recorders has been marked by significant variations in procedures and selected parameters. These variations cause difficulty in comparing such specifications and test results. In July 1989, and again in May 2005, the U.S. Geological Survey hosted international pub-lic/private workshops with the goal of defining widely accepted guidelines for the testing of seismological inertial sensors, seismometers, and accelerometers. The Proceedings of the 2005 workshop have been published and include as appendix 6 the report of the 1989 workshop. This document represents a collation and rationalization of a single set of formal guidelines for testing and specifying broadband seismometers and accelerometers.

  19. Study of the Dynamics of Large Reflector Antennas with Accelerometers

    CERN Document Server

    Snel, R C; Baars, J W M

    2007-01-01

    The Atacama Large Millimeter Array (ALMA) will consist of up to 64 state-of-the-art sub-mm telescopes, subject to stringent performance specifications which will push the boundaries of the technology, and makes testing of antenna performance a likewise challenging task. Two antenna prototypes were evaluated at the ALMA Test Facility at the Very Large Array site in New Mexico, USA. The dynamic behaviour of the antennas under operational conditions was investigated with the help of an accelerometer system capable of measuring rigid body motion of the elevation structure of the antenna, as well as a few low-order deformation modes, resulting in dynamic performance numbers for pointing stability, reflector surface stability, path length stability, and structure flexure. Special emphasis was given to wind effects, one of the major factors affecting performance on timescales of seconds to tens of minutes. This paper describes the accelerometer system, its capabilities and limitations, and presents the dynamic perfo...

  20. DEPTracker – Sleep Pattern Tracking with Accelerometer Technology

    DEFF Research Database (Denmark)

    Grode, Jesper Nicolai Riis; Havn, Ib; Svane Hansen, Lars;

    2015-01-01

    REM (Rapid Eye Movement) sleep pattern changes are known to be an early indicator of effective medical treatment of patients with a depression diagnosis. Existing methods to detect REM sleep pattern changes are known to be inaccurate, costly, or otherwise inadequate in normal settings...... of this patient group. In this paper, we demonstrate DEPTracker, a system capable of detecting sleep patterns, and in particular REM sleep. We show that DEPTracker is an accurate, cost-effective and suitable approach for sleep pattern detection in general. Details of the technology used, combining accelerometer...... technology with digital signal analysis is given and illustrates that the system is able to successfully detect REM sleep. The project demonstrates that accelerometers can be mounted on an eye lid and eye movements can be detected, sampled and stored in a database for online real-time analysis or post-sleep...

  1. Accelerometer-Based Event Detector for Low-Power Applications

    OpenAIRE

    József Smidla; Gyula Simon

    2013-01-01

    In this paper, an adaptive, autocovariance-based event detection algorithm is proposed, which can be used with micro-electro-mechanical systems (MEMS) accelerometer sensors to build inexpensive and power efficient event detectors. The algorithm works well with low signal-to-noise ratio input signals, and its computational complexity is very low, allowing its utilization on inexpensive low-end embedded sensor devices. The proposed algorithm decreases its energy consumption by lowering its duty...

  2. Monitoring feeding behaviour of dairy cows using accelerometers

    Directory of Open Access Journals (Sweden)

    Gabriele Mattachini

    2016-03-01

    Full Text Available Monitoring cow behaviour has become increasingly important in understanding the nutrition, production, management of the well being, and overall health of dairy cows. Methods of assessing behavioural activity have changed in recent years, favouring automatic recording techniques. Traditional methods to measure behaviour, such as direct observation or time-lapse video, are labour-intensive and time-consuming. Automated recording devices have become increasingly common to measure behaviour accurately. Thus, the development of automated monitoring systems that can continuously and accurately quantify feeding behaviour are required for efficient monitoring and control of modern and automated dairy farms. The aim of this study was to evaluate the possible use of a 3D accelerometer to record feeding behaviour of dairy cows. Feeding behaviour (feeding time and number of visits to the manger of 12 lactating dairy cows was recorded for approximately 3 h with 3D-accelerometer data loggers (HOBO Pendant G logger. The sensors were positioned in the high part of the neck to monitor head movements. Behaviour was simultaneously recorded using visual observation as a reference. Linear regression analysis between the measurement methods showed that the recorded feeding time (R2=0.90, n=12, P<0.001 was closely related to visual observations. In contrast, the number of visits was inadequately recorded by the 3D-accelerometer, showing a poor relationship with visual observations (R2=0.31, n=12, P<0.06. Results suggest that the use of accelerometer sensors can be a reliable and suitable technology for monitoring feeding behaviour of individual dairy cows in free stall housing. However, further research is necessary to develop an appropriate device able to detect and recognise the movements connected with the head movement during feeding. Such a device could be part of an automatic livestock management tool for the efficient monitoring and control of comfort and

  3. Analysis of animal accelerometer data using hidden Markov models

    OpenAIRE

    Leos-Barajas, Vianey; Photopoulou, Theoni; Langrock, Roland; Patterson, Toby A; Watanabe, Yuuki; Murgatroyd, Megan; Papastamatiou, Yannis P.

    2016-01-01

    Use of accelerometers is now widespread within animal biotelemetry as they provide a means of measuring an animal's activity in a meaningful and quantitative way where direct observation is not possible. In sequential acceleration data there is a natural dependence between observations of movement or behaviour, a fact that has been largely ignored in most analyses. Analyses of acceleration data where serial dependence has been explicitly modelled have largely relied on hidden Markov models (H...

  4. Denoising and Trend Terms Elimination Algorithm of Accelerometer Signals

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2016-01-01

    Full Text Available Acceleration-based displacement measurement approach is often used to measure the polish rod displacement in the oilfield pumping well. Random noises and trend terms of the accelerometer signals are the main factors that affect the measuring accuracy. In this paper, an efficient online learning algorithm is proposed to improve the measurement precision of polish rod displacement in the oilfield pumping well. To remove the random noises and eliminate the trend term of accelerometer signals, the ARIMA model and its parameters are firstly derived by using the obtained data of time series of acceleration sensor signals. Secondly, the period of the accelerometer signals is estimated through the Rife-Jane frequency estimation approach based on Fast Fourier Transform. With the obtained model and parameters, the random noises are removed by employing the Kalman filtering algorithm. The quadratic integration of the period is calculated to obtain the polish rod displacement. Moreover, the windowed recursive least squares algorithm is implemented to eliminate the trend terms. The simulation results demonstrate that the proposed online learning algorithm is able to remove the random noises and trend terms effectively and greatly improves the measurement accuracy of the displacement.

  5. Modeling and non-linear responses of MEMS capacitive accelerometer

    Directory of Open Access Journals (Sweden)

    Sri Harsha C.

    2014-01-01

    Full Text Available A theoretical investigation of an electrically actuated beam has been illustrated when the electrostatic-ally actuated micro-cantilever beam is separated from the electrode by a moderately large gap for two distinct types of geometric configurations of MEMS accelerometer. Higher order nonlinear terms have been taken into account for studying the pull in voltage analysis. A nonlinear model of gas film squeezing damping, another source of nonlinearity in MEMS devices is included in obtaining the dynamic responses. Moreover, in the present work, the possible source of nonlinearities while formulating the mathematical model of a MEMS accelerometer and their influences on the dynamic responses have been investigated. The theoretical results obtained by using MATLAB has been verified with the results obtained in FE software and has been found in good agreement. Criterion towards stable micro size accelerometer for each configuration has been investigated. This investigation clearly provides an understanding of nonlinear static and dynamics characteristics of electrostatically micro cantilever based device in MEMS.

  6. Determination of gait events using an externally mounted shank accelerometer.

    Science.gov (United States)

    Sinclair, Jonathan; Hobbs, Sarah J; Protheroe, Laurence; Edmundson, Christopher J; Greenhalgh, Andrew

    2013-02-01

    Biomechanical analysis requires the determination of specific foot contact events. This is typically achieved using force platform information; however, when force platforms are unavailable, alternative methods are necessary. A method was developed for the determination of gait events using an accelerometer mounted to the distal tibia, measuring axial accelerations. The aim of the investigation was to determine the efficacy of this method. Sixteen participants ran at 4.0 m/s ± 5%. Synchronized tibial accelerations and vertical ground reaction forces were sampled at 1000 Hz as participants struck a force platform with their dominant foot. Events determined using the accelerometer, were compared with the corresponding events determined using the force platform. Mean errors of 1.68 and 5.46 ms for average and absolute errors were observed for heel strike and of -3.59 and 5.00 ms for toe-off. Mean and absolute errors of 5.18 and 11.47 ms were also found for the duration of the stance phase. Strong correlations (r = .96) were also observed between duration of stance obtained using the two different methods. The error values compare favorably to other alternative methods of predicting gait events. This suggests that shank-mounted accelerometers can be used to accurately and reliably detect gait events. PMID:23462448

  7. High resolution interface circuit for closed-loop accelerometer*

    Institute of Scientific and Technical Information of China (English)

    Yin Liang; Liu Xiaowei; Chen Weiping; Zhou Zhiping

    2011-01-01

    This paper reports a low noise switched-capacitor CMOS interface circuit for the closed-loop operation of a capacitive accelerometer. The time division multiplexing of the same electrode is adopted to avoid the strong feedthrough between capacitance sensing and electrostatic force feedback. A PID controller is designed to ensure the stability and dynamic response o fa high Q closed-loop accelerometer with a vacuum package. The architecture only requires single ended operational amplifiers, transmission gates and capacitors. Test results show that a full scale acceleration of ±3 g, non-linearity of 0.05% and signal bandwidth of 1000 Hz are achieved. The complete module operates from a ±5 V supply and has a measured sensitivity of 1.2 V/g with a noise of floor of 0.8μg/√(Hz) in closed-loop. The chip is fabricated in the 2 μm two-metal and two-poly n-well CMOS process with an area of 15.2 mm2. These results prove that this circuit is suitable for high performance micro-accelerometer applications like seismic detection and oil exploration.

  8. Development of Dual-Axis MEMS Accelerometers for Machine Tools Vibration Monitoring

    Directory of Open Access Journals (Sweden)

    Chih-Yung Huang

    2016-07-01

    Full Text Available With the development of intelligent machine tools, monitoring the vibration by the accelerometer is an important issue. Accelerometers used for measuring vibration signals during milling processes require the characteristics of high sensitivity, high resolution, and high bandwidth. A commonly used accelerometer is the lead zirconate titanate (PZT type; however, integrating it into intelligent modules is excessively expensive and difficult. Therefore, the micro electro mechanical systems (MEMS accelerometer is an alternative with the advantages of lower price and superior integration. In the present study, we integrated two MEMS accelerometer chips into a low-pass filter and housing to develop a low-cost dual-axis accelerometer with a bandwidth of 5 kHz and a full scale range of ±50 g for measuring machine tool vibration. In addition, a platform for measuring the linearity, cross-axis sensitivity and frequency response of the MEMS accelerometer by using the back-to-back calibration method was also developed. Finally, cutting experiments with steady and chatter cutting were performed to verify the results of comparing the MEMS accelerometer with the PZT accelerometer in the time and frequency domains. The results demonstrated that the dual-axis MEMS accelerometer is suitable for monitoring the vibration of machine tools at low cost.

  9. Quality control methods in accelerometer data processing: identifying extreme counts.

    Directory of Open Access Journals (Sweden)

    Carly Rich

    Full Text Available BACKGROUND: Accelerometers are designed to measure plausible human activity, however extremely high count values (EHCV have been recorded in large-scale studies. Using population data, we develop methodological principles for establishing an EHCV threshold, propose a threshold to define EHCV in the ActiGraph GT1M, determine occurrences of EHCV in a large-scale study, identify device-specific error values, and investigate the influence of varying EHCV thresholds on daily vigorous PA (VPA. METHODS: We estimated quantiles to analyse the distribution of all accelerometer positive count values obtained from 9005 seven-year old children participating in the UK Millennium Cohort Study. A threshold to identify EHCV was derived by differentiating the quantile function. Data were screened for device-specific error count values and EHCV, and a sensitivity analysis conducted to compare daily VPA estimates using three approaches to accounting for EHCV. RESULTS: Using our proposed threshold of ≥ 11,715 counts/minute to identify EHCV, we found that only 0.7% of all non-zero counts measured in MCS children were EHCV; in 99.7% of these children, EHCV comprised < 1% of total non-zero counts. Only 11 MCS children (0.12% of sample returned accelerometers that contained negative counts; out of 237 such values, 211 counts were equal to -32,768 in one child. The medians of daily minutes spent in VPA obtained without excluding EHCV, and when using a higher threshold (≥19,442 counts/minute were, respectively, 6.2% and 4.6% higher than when using our threshold (6.5 minutes; p<0.0001. CONCLUSIONS: Quality control processes should be undertaken during accelerometer fieldwork and prior to analysing data to identify monitors recording error values and EHCV. The proposed threshold will improve the validity of VPA estimates in children's studies using the ActiGraph GT1M by ensuring only plausible data are analysed. These methods can be applied to define appropriate EHCV

  10. Exploring the possibilities for star-tracker assisted calibration of the six individual GOCE accelerometers

    OpenAIRE

    Visser, P N A M

    2008-01-01

    A method has been developed and tested for estimating calibration parameters for the six accelerometers on board the Gravity field and steady-state Ocean Circulation Explorer (GOCE) from star tracker observations. These six accelerometers are part of the gradiometer, which is the prime instrument on board GOCE. It will be shown that by taking appropriate combinations of observations collected by the accelerometers, by modeling acceleration terms caused by gravity gradients from an a priori lo...

  11. Development of a quartz digital accelerometer for environmental sensing and navigation applications

    Energy Technology Data Exchange (ETDEWEB)

    Kass, W.J.; Vianco, P.T.

    1993-03-01

    A quartz digital accelerometer has been developed which uses double ended tuning forks as the active sensing elements. The authors have demonstrated the ability of this accelerometer to be capable of acceleration measurements between {+-}150G with {+-}0.5G accuracy. They have further refined the original design and assembly processes to produce accelerometers with < 1mG stability in inertial measurement applications. This report covers the development, design, processing, assembly, and testing of these devices.

  12. The Impact of Gait Disability on the Calibration of Accelerometer Output in Adults with Multiple Sclerosis

    OpenAIRE

    Weikert, Madeline; Dlugonski, Deirdre; Suh, Yoojin; Fernhall, Bo; Motl, Robert W.

    2011-01-01

    Accelerometer activity counts have been correlated with energy expenditure during treadmill walking among ambulatory adults with multiple sclerosis (MS). This study examined the effects of gait disability on 1) the association between rates of energy expenditure and accelerometer output in overground walking and 2) the calibration of accelerometer output for quantifying time spent in moderate-to-vigorous physical activity (MVPA) in people with MS. The sample consisted of 24 individuals with M...

  13. Principle Research on a Single Mass Piezoelectric Six-Degrees-of-Freedom Accelerometer

    OpenAIRE

    Jingcheng Liu; Min Li; Lan Qin; Jun Liu

    2013-01-01

    A signal mass piezoelectric six-degrees-of-freedom (six-DOF) accelerometer is put forward in response to the need for health monitoring of the dynamic vibration characteristics of high grade digitally controlled machine tools. The operating principle of the piezoelectric six-degrees-of-freedom accelerometer is analyzed, and its structure model is constructed. The numerical simulation model (finite element model) of the six axis accelerometer is established. Piezoelectric quartz is chosen for ...

  14. Flextensional fiber Bragg grating-based accelerometer for low frequency vibration measurement

    Institute of Scientific and Technical Information of China (English)

    Jinghua Zhang; Xueguang Qiao; Manli Hu; Zhongyao Feng; Hong Gao; Yang Yang; Rui Zhou

    2011-01-01

    @@ The intelligent structural health monitoring method,which uses a fiber Bragg grating(FBG)sensor,is a new approach in the field of civil engineering.However,it lacks a reliable FBG-based accelerometer for taking structural low frequency vibration measurements.In this letter,a flextensional FBG-based accelerometer is proposed and demonstrated.The experimental results indicate that the natural frequency of the developed accelerometer is 16.7 Hz,with a high sensitivity of 410.7 pm/g.In addition,it has a broad and flat response over low frequencies ranging from 1 to 10 Hz.The natural frequency and sensitivity of the accelerometer can be tuned by adding mass to tailor the sensor performance to specific applications.Experimental results are presented to demonstrate the good performance of the proposed FBG-based accelerometer.These results show that the proposed accelerometer is satisfactory for low frequency vibration measurements.%The intelligent structural health monitoring method, which uses a fiber Bragg grating {FBG} sensor, ie a new approach in the field of civil engineering. However, it lacks a reliable FBG-based accelerometer for taking structural low frequency vibration measurements. In this letter, a flextensional FBG-based accelerometer is proposed and demonstrated. The experimental results indicate that the natural frequency of the developed accelerometer is 16.7 Hz, with a high sensitivity of 410.7 pm/g. In addition, it has a broad and flat response over low frequencies ranging from 1 to 10 Hz. The natural frequency and sensitivity of the accelerometer can be tuned by adding mass to tailor the sensor performance to specific applications. Experimental results are presented to demonstrate the good performance of the proposed FBG-based accelerometer. These results show that the proposed accelerometer is satisfactory for low frequency vibration measurements.

  15. System Wide Joint Position Sensor Fault Tolerance in Robot Systems Using Cartesian Accelerometers

    Science.gov (United States)

    Aldridge, Hal A.; Juang, Jer-Nan

    1997-01-01

    Joint position sensors are necessary for most robot control systems. A single position sensor failure in a normal robot system can greatly degrade performance. This paper presents a method to obtain position information from Cartesian accelerometers without integration. Depending on the number and location of the accelerometers. the proposed system can tolerate the loss of multiple position sensors. A solution technique suitable for real-time implementation is presented. Simulations were conducted using 5 triaxial accelerometers to recover from the loss of up to 4 joint position sensors on a 7 degree of freedom robot moving in general three dimensional space. The simulations show good estimation performance using non-ideal accelerometer measurements.

  16. Interest of the MICROSTAR Accelerometer to improve the GRASP Mission.

    Science.gov (United States)

    Perrot, E.; Lebat, V.; Foulon, B.; Christophe, B.; Liorzou, F.; Huynh, P. A.

    2015-12-01

    The Geodetic Reference Antenna in Space (GRASP) is a micro satellite mission concept proposed by JPL to improve the definition of the Terrestrial Reference Frame (TRF). GRASP collocates GPS, SLR, VLBI, and DORIS sensors on a dedicated spacecraft in order to establish precise and stable ties between the key geodetic techniques used to define and disseminate the TRF. GRASP also offers a space-based reference antenna for the present and future Global Navigation Satellite Systems (GNSS). By taking advantage of the new testing possibilities offer by the catapult facility at the ZARM drop tower, the ONERA's space accelerometer team proposes an up-dated version, called MICROSTAR, of its ultra sensitive electrostatic accelerometers which have contributed to the success of the last Earth's gravity missions GRACE and GOCE. Built around a cubic proof-mass, it provides the 3 linear accelerations with a resolution better than 10-11 ms-2/Hz1/2 into a measurement bandwidth between 10-3 Hz and 0.1 Hz and the 3 angular accelerations about its 3 orthogonal axes with 5´10-10 rad.s-2/Hz1/2 resolution. Integrated at the centre of mass of the satellite, MICROSTAR improves the Precise Orbit Determination (POD) by accurate measurement of the non-gravitational force acting on the satellite. It offers also the possibility to calibrate the change in the position of the satellite center of mass with an accuracy better than 100 μm as demonstrated in the GRACE mission. Assuming a sufficiently rigid structure between the antennas and the accelerometer, its data can participate to reach the mission objective of 1 mm precision for the TRF position.

  17. Characterisation of a highly symmetrical miniature capacitive triaxial accelerometer

    OpenAIRE

    Lotters, J.C.; Olthuis, W.; Veltink, P.H.; Bergveld, P.

    1997-01-01

    A highly symmetrical cubic capacitive triaxial accelerometer for biomedical applications has been designed, realised and tested. The sensors are available in two outer dimensions, namely 2×2×2 and 5×5×5 mm3. The devices are mounted on a standard IC package for easy testing. Features of the sensor are a highly symmetrical cubic structure, capacitive coupling of the high frequency input voltage to the seismic mass and the use of the polymers polydimethylsiloxane (PDMS) as spring material betwee...

  18. Triaxial MEMS accelerometer with screen printed PZT thick film

    DEFF Research Database (Denmark)

    Hindrichsen, Christian Carstensen; Almind, Ninia Sejersen; Brodersen, Simon Hedegaard;

    2010-01-01

    . In this work integration of a screen printed piezoelectric PZT thick film with silicon MEMS technology is shown. A high bandwidth triaxial accelerometer has been designed, fabricated and characterized. The voltage sensitivity is 0.31 mV/g in the vertical direction, 0.062 mV/g in the horizontal direction......Piezoelectric thick films have increasing interest due to the potential high sensitivity and actuation force for MEMS sensors and actuators. The screen printing technique is a promising deposition technique for realizing piezoelectric thick films in the thickness range from 10-100 mu m...

  19. Technique for Determining Bridge Displacement Response Using MEMS Accelerometers.

    Science.gov (United States)

    Sekiya, Hidehiko; Kimura, Kentaro; Miki, Chitoshi

    2016-02-19

    In bridge maintenance, particularly with regard to fatigue damage in steel bridges, it is important to determine the displacement response of the entire bridge under a live load as well as that of each member. Knowing the displacement response enables the identification of dynamic deformations that can cause stresses and ultimately lead to damage and thus also allows the undertaking of appropriate countermeasures. In theory, the displacement response can be calculated from the double integration of the measured acceleration. However, data measured by an accelerometer include measurement errors caused by the limitations of the analog-to-digital conversion process and sensor noise. These errors distort the double integration results. Furthermore, as bridges in service are constantly vibrating because of passing vehicles, estimating the boundary conditions for the numerical integration is difficult. To address these problems, this paper proposes a method for determining the displacement of a bridge in service from its acceleration based on its free vibration. To verify the effectiveness of the proposed method, field measurements were conducted using nine different accelerometers. Based on the results of these measurements, the proposed method was found to be highly accurate in comparison with the reference displacement obtained using a contact displacement gauge.

  20. Technique for Determining Bridge Displacement Response Using MEMS Accelerometers

    Directory of Open Access Journals (Sweden)

    Hidehiko Sekiya

    2016-02-01

    Full Text Available In bridge maintenance, particularly with regard to fatigue damage in steel bridges, it is important to determine the displacement response of the entire bridge under a live load as well as that of each member. Knowing the displacement response enables the identification of dynamic deformations that can cause stresses and ultimately lead to damage and thus also allows the undertaking of appropriate countermeasures. In theory, the displacement response can be calculated from the double integration of the measured acceleration. However, data measured by an accelerometer include measurement errors caused by the limitations of the analog-to-digital conversion process and sensor noise. These errors distort the double integration results. Furthermore, as bridges in service are constantly vibrating because of passing vehicles, estimating the boundary conditions for the numerical integration is difficult. To address these problems, this paper proposes a method for determining the displacement of a bridge in service from its acceleration based on its free vibration. To verify the effectiveness of the proposed method, field measurements were conducted using nine different accelerometers. Based on the results of these measurements, the proposed method was found to be highly accurate in comparison with the reference displacement obtained using a contact displacement gauge.

  1. Shock margin testing of a one-axis MEMS accelerometer.

    Energy Technology Data Exchange (ETDEWEB)

    Parson, Ted Blair; Tanner, Danelle Mary; Buchheit, Thomas Edward

    2008-07-01

    Shock testing was performed on a selected commercial-off-the-shelf - MicroElectroMechanical System (COTS-MEMS) accelerometer to determine the margin between the published absolute maximum rating for shock and the 'measured' level where failures are observed. The purpose of this testing is to provide baseline data for isolating failure mechanisms under shock and environmental loading in a representative device used or under consideration for use within systems and assemblies of the DOD/DOE weapons complex. The specific device chosen for this study was the AD22280 model of the ADXL78 MEMS Accelerometer manufactured by Analog Devices Inc. This study focuses only on the shock loading response of the device and provides the necessary data for adding influence of environmental exposure to the reliability of this class of devices. The published absolute maximum rating for acceleration in any axis was 4000 G for this device powered or unpowered. Results from this study showed first failures at 8000 G indicating a margin of error of two. Higher shock level testing indicated that an in-plane, but off-axis acceleration was more damaging than one in the sense direction.

  2. Evolution of accelerometer methods for physical activity research.

    Science.gov (United States)

    Troiano, Richard P; McClain, James J; Brychta, Robert J; Chen, Kong Y

    2014-07-01

    The technology and application of current accelerometer-based devices in physical activity (PA) research allow the capture and storage or transmission of large volumes of raw acceleration signal data. These rich data not only provide opportunities to improve PA characterisation, but also bring logistical and analytic challenges. We discuss how researchers and developers from multiple disciplines are responding to the analytic challenges and how advances in data storage, transmission and big data computing will minimise logistical challenges. These new approaches also bring the need for several paradigm shifts for PA researchers, including a shift from count-based approaches and regression calibrations for PA energy expenditure (PAEE) estimation to activity characterisation and EE estimation based on features extracted from raw acceleration signals. Furthermore, a collaborative approach towards analytic methods is proposed to facilitate PA research, which requires a shift away from multiple independent calibration studies. Finally, we make the case for a distinction between PA represented by accelerometer-based devices and PA assessed by self-report.

  3. Huygens probe entry dynamic model and accelerometer data analysis

    Science.gov (United States)

    Colombatti, Giacomo; Aboudan, Alessio; Ferri, Francesca; Angrilli, Francesco

    2008-04-01

    During the first phase of Huygens arrival into Titan's atmosphere the probe is subjected to gravitational and aerodynamic forces in aerodynamic hypersonic regime. Atmospheric drag exerts a strong deceleration on the capsule measured by Huygens atmospheric structure instrument (HASI) servo accelerometer. A 6 DOF (Degree of Freedom) model of the Huygens probe entry dynamics has been developed and used for data analysis. The accelerometer data are analysed and the model allows the retrieval of dynamics information of Huygens probe from 1545 km altitude down to end of the entry phase. Probe's initial conditions (velocity and position) were refined to match the measured deceleration profile resulting in a different altitude at interface epoch with respect to those of the Cassini Navigation Team. Velocity and position of probe at interface epoch are compatible with those used by Descent Trajectory Working Group (DTWG). Measurements acquired before atmosphere detection are used to estimate probe's angular rate, bound attitude and characterise the angle of attack profile which results to be lower than 4∘ during the whole entry. Probe's spin calculated (6.98 RPM) is slightly different with respect to DTWG of 7.28 RPM but considering a 2% error in the Inertia matrix these results are inside the 1-σ error band.

  4. Optimal GPS/accelerometer integration algorithm for monitoring the vertical structural dynamics

    Science.gov (United States)

    Meng, Xiaolin; Wang, Jian; Han, Houzeng

    2014-11-01

    The vertical structural dynamics is a crucial factor for structural health monitoring (SHM) of civil structures such as high-rise buildings, suspension bridges and towers. This paper presents an optimal GPS/accelerometer integration algorithm for an automated multi-sensor monitoring system. The closed loop feedback algorithm for integrating the vertical GPS and accelerometer measurements is proposed based on a 5 state extended KALMAN filter (EKF) and then the narrow moving window Fast Fourier Transform (FFT) analysis is applied to extract structural dynamics. A civil structural vibration is simulated and the analysed result shows the proposed algorithm can effectively integrate the online vertical measurements produced by GPS and accelerometer. Furthermore, the accelerometer bias and scale factor can also be estimated which is impossible with traditional integration algorithms. Further analysis shows the vibration frequencies detected in GPS or accelerometer are all included in the integrated vertical defection time series and the accelerometer can effectively compensate the short-term GPS outages with high quality. Finally, the data set collected with a time synchronised and integrated GPS/accelerometer monitoring system installed on the Nottingham Wilford Bridge when excited by 15 people jumping together at its mid-span are utilised to verify the effectiveness of this proposed algorithm. Its implementations are satisfactory and the detected vibration frequencies are 1.720 Hz, 1.870 Hz, 2.104 Hz, 2.905 Hz and also 10.050 Hz, which is not found in GPS or accelerometer only measurements.

  5. Exploring the possibilities for star-tracker assisted calibration of the six individual GOCE accelerometers

    NARCIS (Netherlands)

    Visser, P.N.A.M.

    2008-01-01

    A method has been developed and tested for estimating calibration parameters for the six accelerometers on board the Gravity field and steady-state Ocean Circulation Explorer (GOCE) from star tracker observations. These six accelerometers are part of the gradiometer, which is the prime instrument on

  6. A new z-axis resonant micro-accelerometer based on electrostatic stiffness.

    Science.gov (United States)

    Yang, Bo; Wang, Xingjun; Dai, Bo; Liu, Xiaojun

    2015-01-05

    Presented in the paper is the design, the simulation, the fabrication and the experiment of a new z-axis resonant accelerometer based on the electrostatic stiffness. The new z-axis resonant micro-accelerometer, which consists of a torsional accelerometer and two plane resonators, decouples the sensing movement of the accelerometer from the oscillation of the plane resonators by electrostatic stiffness, which will improve the performance. The new structure and the sensitive theory of the acceleration are illuminated, and the equation of the scale factor is deduced under ideal conditions firstly. The Ansys simulation is implemented to verify the basic principle of the torsional accelerometer and the plane resonator individually. The structure simulation results prove that the effective frequency of the torsional accelerometer and the plane resonator are 0.66 kHz and 13.3 kHz, respectively. Then, the new structure is fabricated by the standard three-mask deep dry silicon on glass (DDSOG) process and encapsulated by parallel seam welding. Finally, the detecting and control circuits are designed to achieve the closed-loop self-oscillation, to trace the natural frequency of resonator and to measure the system frequency. Experimental results show that the new z-axis resonant accelerometer has a scale factor of 31.65 Hz/g, a bias stability of 727 µg and a dynamic range of over 10 g, which proves that the new z-axis resonant micro-accelerometer is practicable.

  7. A New Z-axis Resonant Micro-Accelerometer Based on Electrostatic Stiffness

    Directory of Open Access Journals (Sweden)

    Bo Yang

    2015-01-01

    Full Text Available Presented in the paper is the design, the simulation, the fabrication and the experiment of a new z-axis resonant accelerometer based on the electrostatic stiffness. The new z-axis resonant micro-accelerometer, which consists of a torsional accelerometer and two plane resonators, decouples the sensing movement of the accelerometer from the oscillation of the plane resonators by electrostatic stiffness, which will improve the performance. The new structure and the sensitive theory of the acceleration are illuminated, and the equation of the scale factor is deduced under ideal conditions firstly. The Ansys simulation is implemented to verify the basic principle of the torsional accelerometer and the plane resonator individually. The structure simulation results prove that the effective frequency of the torsional accelerometer and the plane resonator are 0.66 kHz and 13.3 kHz, respectively. Then, the new structure is fabricated by the standard three-mask deep dry silicon on glass (DDSOG process and encapsulated by parallel seam welding. Finally, the detecting and control circuits are designed to achieve the closed-loop self-oscillation, to trace the natural frequency of resonator and to measure the system frequency. Experimental results show that the new z-axis resonant accelerometer has a scale factor of 31.65 Hz/g, a bias stability of 727 µg and a dynamic range of over 10 g, which proves that the new z-axis resonant micro-accelerometer is practicable.

  8. The kinematics of the swing phase obtained from accelerometer and gyroscope measurements

    NARCIS (Netherlands)

    Heyn, Andreas; Mayagoitia, Ruth E.; Nene, Anand V.; Veltink, Peter H.

    1996-01-01

    The kinematics needed to calculate the knee moment during the initial swing phase were obtained from a set of eight leg-mounted uni-axial accelerometers and two gyroscopes. The angular and linear accelerations of shank and thigh were calculated from the signals of two accelerometers mounted on each

  9. Development of a novel accelerometer based on an overlay detection bridge

    Institute of Scientific and Technical Information of China (English)

    Du Chunhui; He Changde; Ge Xiaoyang; Zhang Yongping; Yu Jiaqi; Song Xiaopeng; Zhang Wendong

    2013-01-01

    This paper describes the design,simulation,processing and test result of a high sensitivity accelerometer based on the piezoresistive effect which uses an overlay bridge detection method.The structure of this accelerometer is supersymmetric "mass-beams".This accelerometer has 8 beams,where two varistors are put in the two ends.Four varistors compose a Wheatstone bridge and the output voltages of the 4 Wheatstone bridges have been superimposed as the final output voltage.The sensitivity of the accelerometer can be improved effectively by these clever methods.A simplified mathematical model has been created to analyze the mechanical properties of the sensor,then the finite element modeling and simulation have been used to verify the feasibility of the accelerometer.The results show that the sensitivity of the accelerometer is 1.1381 mV/g,which is about four times larger than that of the single bridge accelerometers and series bridge sensor.The bandwidth is 0-1000 Hz which is equal to that of the single bridge accelerometers and the series bridge sensor.The comparison reveals that the new overlay detection bridge method can improve the sensitivity of the sensor in the same bandwidth.Meanwhile,this method provides an effective method to improve the sensitivity ofpiezoresistive sensors.

  10. High shock, high frequency characteristics of a mechanical isolator for a piezoresistive accelerometer

    Energy Technology Data Exchange (ETDEWEB)

    Bateman, V.I.; Brown, F.A.; Davie, N.T. [and others

    1995-07-01

    A mechanical isolator has been developed for a piezoresistive accelerometer. The purpose of the isolator is to mitigate high frequency shocks before they reach the accelerometer because the high frequency shocks may cause the accelerometer to resonate. Since the accelerometer is undamped, it often breaks when it resonates. The mechanical isolator was developed in response to impact test requirements for a variety of structures at Sandia National Laboratories. An Extended Technical Assistance Program with the accelerometer manufacturer has resulted in a commercial isolator that will be available to the general public. This mechanical isolator has ten times the bandwidth of any other commercial isolator and has acceptable frequency domain performance from DC to 10 kHz ({plus_minus} 10%) over a temperature range of -65{degrees}F to +185{degrees}F as demonstrated in this paper.

  11. Influence of allowable interruption period on estimates of accelerometer wear time and sedentary time in older adults

    OpenAIRE

    Mailey, Emily L; Gothe, Neha P.; Wójcicki, Thomas R.; Szabo, Amanda N.; Olson, Erin A.; Mullen, Sean P.; Fanning, Jason T.; Motl, Robert W.; McAuley, Edward

    2013-01-01

    The criteria one uses to reduce accelerometer data can profoundly influence the interpretation of research outcomes. The purpose of this study was to examine the influence of three different interruption periods (i.e., 20, 30, and 60 minutes) on the amount of data retained for analyses and estimates of sedentary time among older adults. Older adults (N=311; Mage=71.1) wore an accelerometer for seven days and reported wear time on an accelerometer log. Accelerometer data were downloaded and sc...

  12. Slice&Dice: Recognizing Food Preparation Activities Using Embedded Accelerometers

    Science.gov (United States)

    Pham, Cuong; Olivier, Patrick

    Within the context of an endeavor to provide situated support for people with cognitive impairments in the kitchen, we developed and evaluated classifiers for recognizing 11 actions involved in food preparation. Data was collected from 20 lay subjects using four specially designed kitchen utensils incorporating embedded 3-axis accelerometers. Subjects were asked to prepare a mixed salad in our laboratory-based instrumented kitchen environment. Video of each subject's food preparation activities were independently annotated by three different coders. Several classifiers were trained and tested using these features. With an overall accuracy of 82.9% our investigation demonstrated that a broad set of food preparation actions can be reliably recognized using sensors embedded in kitchen utensils.

  13. Accelerometer-Based Event Detector for Low-Power Applications

    Directory of Open Access Journals (Sweden)

    József Smidla

    2013-10-01

    Full Text Available In this paper, an adaptive, autocovariance-based event detection algorithm is proposed, which can be used with micro-electro-mechanical systems (MEMS accelerometer sensors to build inexpensive and power efficient event detectors. The algorithm works well with low signal-to-noise ratio input signals, and its computational complexity is very low, allowing its utilization on inexpensive low-end embedded sensor devices. The proposed algorithm decreases its energy consumption by lowering its duty cycle, as much as the event to be detected allows it. The performance of the algorithm is tested and compared to the conventional filter-based approach. The comparison was performed in an application where illegal entering of vehicles into restricted areas was detected.

  14. Stress relaxation insensitive designs for metal compliant mechanism threshold accelerometers

    Directory of Open Access Journals (Sweden)

    Carlos Vilorio

    2015-12-01

    Full Text Available We present two designs for metal compliant mechanisms for use as threshold accelerometers which require zero external power. Both designs rely on long, thin flexures positioned orthogonally to a flat body. The first design involves cutting or stamping a thin spring-steel sheet and then bending elements to form the necessary thin flexors. The second design uses precut spring-steel flexure elements mounted into a mold which is then filled with molten tin to form a bimetallic device. Accelerations necessary to switch the devices between bistable states were measured using a centrifuge. Both designs showed very little variation in threshold acceleration due to stress relaxation over a period of several weeks. Relatively large variations in threshold acceleration were observed for devices of the same design, most likely due to variations in the angle of the flexor elements relative to the main body of the devices.

  15. ISLES: Probing Extra Dimensions Using a Superconducting Accelerometer

    Science.gov (United States)

    Paik, Ho Jung; Moody, M. Vol; Prieto-Gortcheva, Violeta A.

    2003-01-01

    In string theories, extra dimensions must be compactified. The possibility that gravity can have large radii of compactification leads to a violation of the inverse square law at submillimeter distances. The objective of ISLES is to perform a null test of Newton s law in space with a resolution of one part in 10(exp 5) or better at 100 microns. The experiment will be cooled to less than or equal to 2 K, which permits superconducting magnetic levitation of the test masses. To minimize Newtonian errors, ISLES employs a near null source, a circular disk of large diameter-to-thickness ratio. Two test masses, also disk-shaped, are suspended on the two sides of the source mass at a nominal distance of 100 microns. The signal is detected by a superconducting differential accelerometer. A ground test apparatus is under construction.

  16. Improving energy expenditure estimation by using a triaxial accelerometer.

    Science.gov (United States)

    Chen, K Y; Sun, M

    1997-12-01

    In our study of 125 subjects (53 men and 72 women) for two 24-h periods, we validated energy expenditure (EE), estimated by a triaxial accelerometer (Tritrac-R3D), by using a whole-room indirect calorimeter under close-to-normal living conditions. The estimated EE was correlated with the measured total EE for the 2 days (r = 0. 925 and r = 0.855; P linear and a nonlinear model to predict EE by using the acceleration components from the Tritrac. Predicted EE was significantly improved with both models in estimating total EE, total EE for physical activities, EE in low-intensity activities, minute-by-minute averaged relative difference, and minute-by-minute SEE (all P acceleration, EE can be estimated with higher accuracy (averaged SEE = 0.418 W/kg) than with the Tritrac model.

  17. Circular Piezoelectric Accelerometer for High Band Width Application

    DEFF Research Database (Denmark)

    Hindrichsen, Christian Carstensen; Larsen, Jack; Lou-Møller, Rasmus;

    2009-01-01

    An uniaxial bulk-micromachined piezoelectric MEMS accelerometer intended for high bandwidth application is fabricated and characterized. A circular seismic mass (radius = 1200 ¿m) is suspended by a 20 ¿m thick annular silicon membrane (radius = 1800 ¿m). A 24 ¿m PZT screen printed thick film...... is used as the sensing material on top of the silicon membrane. Accelerations in the out of plane direction induce a force on the seismic mass bending the membrane and a potential difference is measured in the out of plane direction of the stressed PZT. A resonance frequency of 23.50 kHz, a charge...

  18. A brief test of the Hewlett-Packard MEMS seismic accelerometer

    Science.gov (United States)

    Homeijer, Brian D.; Milligan, Donald J.; Hutt, Charles R.

    2014-01-01

    Testing was performed on a prototype of Hewlett-Packard (HP) Micro-Electro-Mechanical Systems (MEMS) seismic accelerometer at the U.S. Geological Survey’s Albuquerque Seismological Laboratory. This prototype was built using discrete electronic components. The self-noise level was measured during low seismic background conditions and found to be 9.8 ng/√Hz at periods below 0.2 s (frequencies above 5 Hz). The six-second microseism noise was also discernible. The HP MEMS accelerometer was compared to a Geotech Model GS-13 reference seismometer during seismic noise and signal levels well above the self-noise of the accelerometer. Matching power spectral densities (corrected for accelerometer and seismometer responses to represent true ground motion) indicated that the HP MEMS accelerometer has a flat (constant) response to acceleration from 0.0125 Hz to at least 62.5 Hz. Tilt calibrations of the HP MEMS accelerometer verified that the flat response to acceleration extends to 0 Hz. Future development of the HP MEMS accelerometer includes replacing the discreet electronic boards with a low power application-specific integrated circuit (ASIC) and increasing the dynamic range of the sensor to detect strong motion signals above one gravitational acceleration, while maintaining the self-noise observed during these tests.

  19. Triaxial Accelerometer Error Coefficients Identification with a Novel Artificial Fish Swarm Algorithm

    Directory of Open Access Journals (Sweden)

    Yanbin Gao

    2015-01-01

    Full Text Available Artificial fish swarm algorithm (AFSA is one of the state-of-the-art swarm intelligence techniques, which is widely utilized for optimization purposes. Triaxial accelerometer error coefficients are relatively unstable with the environmental disturbances and aging of the instrument. Therefore, identifying triaxial accelerometer error coefficients accurately and being with lower costs are of great importance to improve the overall performance of triaxial accelerometer-based strapdown inertial navigation system (SINS. In this study, a novel artificial fish swarm algorithm (NAFSA that eliminated the demerits (lack of using artificial fishes’ previous experiences, lack of existing balance between exploration and exploitation, and high computational cost of AFSA is introduced at first. In NAFSA, functional behaviors and overall procedure of AFSA have been improved with some parameters variations. Second, a hybrid accelerometer error coefficients identification algorithm has been proposed based on NAFSA and Monte Carlo simulation (MCS approaches. This combination leads to maximum utilization of the involved approaches for triaxial accelerometer error coefficients identification. Furthermore, the NAFSA-identified coefficients are testified with 24-position verification experiment and triaxial accelerometer-based SINS navigation experiment. The priorities of MCS-NAFSA are compared with that of conventional calibration method and optimal AFSA. Finally, both experiments results demonstrate high efficiency of MCS-NAFSA on triaxial accelerometer error coefficients identification.

  20. A triaxial accelerometer monkey algorithm for optimal sensor placement in structural health monitoring

    International Nuclear Information System (INIS)

    Optimal sensor placement (OSP) technique is a vital part of the field of structural health monitoring (SHM). Triaxial accelerometers have been widely used in the SHM of large-scale structures in recent years. Triaxial accelerometers must be placed in such a way that all of the important dynamic information is obtained. At the same time, the sensor configuration must be optimal, so that the test resources are conserved. The recommended practice is to select proper degrees of freedom (DOF) based upon several criteria and the triaxial accelerometers are placed at the nodes corresponding to these DOFs. This results in non-optimal placement of many accelerometers. A ‘triaxial accelerometer monkey algorithm’ (TAMA) is presented in this paper to solve OSP problems of triaxial accelerometers. The EFI3 measurement theory is modified and involved in the objective function to make it more adaptable in the OSP technique of triaxial accelerometers. A method of calculating the threshold value based on probability theory is proposed to improve the healthy rate of monkeys in a troop generation process. Meanwhile, the processes of harmony ladder climb and scanning watch jump are proposed and given in detail. Finally, Xinghai NO.1 Bridge in Dalian is implemented to demonstrate the effectiveness of TAMA. The final results obtained by TAMA are compared with those of the original monkey algorithm and EFI3 measurement, which show that TAMA can improve computational efficiency and get a better sensor configuration. (paper)

  1. The effect of accelerometer location on the classification of single-site forearm mechanomyograms

    Directory of Open Access Journals (Sweden)

    Sejdić Ervin

    2010-06-01

    Full Text Available Abstract Background Recently, pattern recognition methods have been deployed in the classification of multiple activation states from mechanomyogram (MMG signals for the purpose of controlling switching interfaces. Given the propagative properties of MMG signals, it has been suggested that MMG classification should be robust to changes in sensor placement. Nonetheless, this purported robustness remains speculative to date. This study sought to quantify the change in classification accuracy, if any, when a classifier trained with MMG signals from the muscle belly, is subsequently tested with MMG signals from a nearby location. Methods An arrangement of 5 accelerometers was attached to the flexor carpi radialis muscle of 12 able-bodied participants; a reference accelerometer was located over the muscle belly, two peripheral accelerometers were positioned along the muscle's transverse axis and two more were aligned to the muscle's longitudinal axis. Participants performed three classes of muscle activity: wrist flexion, wrist extension and semi-pronation. A collection of time, frequency and time-frequency features were considered and reduced by genetic feature selection. The classifier, trained using features from the reference accelerometer, was tested with signals from the longitudinally and transversally displaced accelerometers. Results Classification degradation due to accelerometer displacement was significant for all participants, and showed no consistent trend with the direction of displacement. Further, the displaced accelerometer signals showed task-dependent de-correlations with respect to the reference accelerometer. Conclusions These results indicate that MMG signal features vary with spatial location and that accelerometer displacements of only 1-2 cm cause sufficient feature drift to significantly diminish classification accuracy. This finding emphasizes the importance of consistent sensor placement between MMG classifier training

  2. A Novel Digital Closed Loop MEMS Accelerometer Utilizing a Charge Pump.

    Science.gov (United States)

    Chu, Yixing; Dong, Jingxin; Chi, Baoyong; Liu, Yunfeng

    2016-01-01

    This paper presents a novel digital closed loop microelectromechanical system (MEMS) accelerometer with the architecture and experimental evaluation. The complicated timing diagram or complex power supply in published articles are circumvented by using a charge pump system of adjustable output voltage fabricated in a 2P4M 0.35 µm complementary metal-oxide semiconductor (CMOS) process, therefore making it possible for interface circuits of MEMS accelerometers to be integrated on a single die on a large scale. The output bitstream of the sigma delta modulator is boosted by the charge pump system and then applied on the feedback comb fingers to form electrostatic forces so that the MEMS accelerometer can operate in a closed loop state. Test results agree with the theoretical formula nicely. The nonlinearity of the accelerometer within ±1 g is 0.222% and the long-term stability is about 774 µg.

  3. CMOS-MEMS Microgravity Accelerometer with High-Precision DC Response Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this Phase II SBIR project a high-sensitivity low-noise all-silicon CMOS-MEMS accelerometer for quasi-steady measurements of accelerations at sub 1 micro-g...

  4. CMOS-MEMS Microgravity Accelerometer with High-Precision DC Response Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I SBIR effort initiates development of a high-sensitivity low-noise all-silicon CMOS-MEMS accelerometer for quasi-steady measurements of accelerations at...

  5. Processing of the signals in precision digital accelerometer with the fiber-optical sensor

    Directory of Open Access Journals (Sweden)

    O. A. Chubarev

    2007-10-01

    Full Text Available The algorithm of processing the signals in precision digital accelerometer with the fiberoptical sensor is brought. Advantages and features of use microcontroller device for processing signals from the fiber-optical sensor are considered.

  6. Electrostatic accelerometer with bias rejection for Gravitation and Solar System physics

    CERN Document Server

    Lenoir, Benjamin; Foulon, Bernard; Christophe, Bruno; Lamine, Brahim; Reynaud, Serge

    2010-01-01

    Radio tracking of interplanetary probes is an important tool for navigation purposes as well as for testing the laws of physics or exploring planetary environments. The addition of an accelerometer on board a spacecraft provides orbit determination specialists and physicists with an additional observable of great interest: it measures the value of the non-gravitational acceleration acting on the spacecraft, i.e. the departure of the probe from geodesic motion. This technology is now routinely used for geodesy missions in Earth orbits with electrostatic accelerometers. This article proposes a technological evolution which consists in adding a subsystem to remove the bias of an electrostatic accelerometer. It aims at enhancing the scientific return of interplanetary missions in the Solar System, from the point of view of fundamental physics as well as Solar System physics. The main part of the instrument is an electrostatic accelerometer called MicroSTAR, which inherits mature technologies based on ONERA's expe...

  7. A Novel Digital Closed Loop MEMS Accelerometer Utilizing a Charge Pump

    Directory of Open Access Journals (Sweden)

    Yixing Chu

    2016-03-01

    Full Text Available This paper presents a novel digital closed loop microelectromechanical system (MEMS accelerometer with the architecture and experimental evaluation. The complicated timing diagram or complex power supply in published articles are circumvented by using a charge pump system of adjustable output voltage fabricated in a 2P4M 0.35 µm complementary metal-oxide semiconductor (CMOS process, therefore making it possible for interface circuits of MEMS accelerometers to be integrated on a single die on a large scale. The output bitstream of the sigma delta modulator is boosted by the charge pump system and then applied on the feedback comb fingers to form electrostatic forces so that the MEMS accelerometer can operate in a closed loop state. Test results agree with the theoretical formula nicely. The nonlinearity of the accelerometer within ±1 g is 0.222% and the long-term stability is about 774 µg.

  8. Accelerometer for Space Applications Based on Light-Pulse Atom Interferometry Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to build a compact, high-precision single-axis accelerometer based on atom interferometry that is applicable to operation in space environments. Based on...

  9. A state-the-art report on the development of the piezoelectric accelerometer sensor

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jee Yun; Oh, Suk Jin; Kim, Kyung Hoh; Kim, Sun Jae; Kang, Dae Kab [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1994-12-01

    A state-of-the art surveys on the application and the manufacturing technology of a piezoelectric accelerometer sensor. An accelerometer sensor is applied to the monitoring of acoustic leak, reactor coolant pump vibration and loose parts in the reactor, and the measurement of vibration and stress of large equipments such as pump, tubes, etc.. The performance of an accelerometer consisted of piezoelectric ceramic, mass, base, case and cable is depend on the characteristics of each component and the assembling method. Sensitivity, linearity and dynamic range, transverse sensitivity, phase response, transient temperature response, frequency response, base strain sensitivity, magnetic sensitivity, acoustic sensitivity, humidity effect and radiation effect must be measured and evaluated for conforming quality of the developed accelerometer sensor. 35 figs., 29 tabs., 38 refs. (Author).

  10. Principle Research on a Single Mass Piezoelectric Six-Degrees-of-Freedom Accelerometer

    Directory of Open Access Journals (Sweden)

    Jingcheng Liu

    2013-08-01

    Full Text Available A signal mass piezoelectric six-degrees-of-freedom (six-DOF accelerometer is put forward in response to the need for health monitoring of the dynamic vibration characteristics of high grade digitally controlled machine tools. The operating principle of the piezoelectric six-degrees-of-freedom accelerometer is analyzed, and its structure model is constructed. The numerical simulation model (finite element model of the six axis accelerometer is established. Piezoelectric quartz is chosen for the acceleration sensing element and conversion element, and its static sensitivity, static coupling interference and dynamic natural frequency, dynamic cross coupling are analyzed by ANSYS software. Research results show that the piezoelectric six-DOF accelerometer has advantages of simple and rational structure, correct sensing principle and mathematic model, good linearity, high rigidity, and theoretical natural frequency is more than 25 kHz, no nonlinear cross coupling and no complex decoupling work.

  11. Characteristics of a piezoresistive accelerometer in shock environments up to 150,000 G

    Energy Technology Data Exchange (ETDEWEB)

    Bateman, V.I.; Davie, N.T.; Brown, F.A.

    1995-03-01

    The characteristics of a piezoresistive accelerometer in shock environments are being studied at Sandia National Laboratories in the Mechanical Shock Testing Laboratory. A Hopkinson bar capability has been developed to extend our undemanding of the piezoresistive accelerometer, in two mechanical configurations, in the high frequency, high shock environments where measurements are being made. Two different Hopkinson bar materials are being used: Titanium and beryllium The in-axis performance of the piezoresistive accelerometer for frequencies of dc-10 kHz and shock magnitudes of up to 150,000 g as determined from measurements with a titanium Hopkinson bar are presented. The beryllium Hopkinson bar configuration is described. Preliminary in-axis characteristics of the piezoresistive accelerometer at a nominal shock level of 50,000 g for a frequency range of DC-30 kHz determined from the beryllium bar are presented.

  12. The use of a beryllium Hopkinson bar to characterize a piezoresistive accelerometer in shock environments

    Energy Technology Data Exchange (ETDEWEB)

    Bateman, V.I.; Brown, F.A.; Davie, N.T.

    1996-03-01

    The characteristics of a piezoresistive accelerometer in shock environments are being studied at Sandia National Laboratories in the Mechanical Shock Testing Laboratory. A Hopkinson bar capability has been developed to extend our understanding of the piezoresistive accelerometer, in two mechanical configurations, in the high frequency, high shock environments where measurements are being made. In this paper, the beryllium Hopkinson bar configuration with a laser doppler vibrometer as the reference measurement is described. The in-axis performance of the piezoresistive accelerometer for frequencies of dc-50 kHz and shock magnitudes of up to 70,000 g as determined from measurements with a beryllium Hopkinson bar are presented. Preliminary results of characterizations of the accelerometers subjected to cross-axis shocks in a split beryllium Hopkinson bar configuration are presented.

  13. Accelerometer for Space Applications Based on Light-Pulse Atom Interferometry Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to design a compact, high-precision, single-axis accelerometer based on atom interferometry that is applicable to operation in space environments. Our...

  14. Feasibility and validity of accelerometer measurements to assess physical activity in toddlers

    Directory of Open Access Journals (Sweden)

    De Bourdeaudhuij Ilse

    2011-06-01

    Full Text Available Abstract Background Accelerometers are considered to be the most promising tool for measuring physical activity (PA in free-living young children. So far, no studies have examined the feasibility and validity of accelerometer measurements in children under 3 years of age. Therefore, the purpose of the present study was to examine the feasibility and validity of accelerometer measurements in toddlers (1- to 3-year olds. Methods Forty-seven toddlers (25 boys; 20 ± 4 months wore a GT1M ActiGraph accelerometer for 6 consecutive days and parental perceptions of the acceptability of wearing the monitor were assessed to examine feasibility. To investigate the validity of the ActiGraph and the predictive validity of three ActiGraph cut points, accelerometer measurements of 31 toddlers (17 boys; 20 ± 4 months during free play at child care were compared to directly observed PA, using the Observational System for Recording Physical Activity in Children-Preschool (OSRAC-P. Validity was assessed using Pearson and Spearman correlations and predictive validity using area under the Receiver Operating Characteristic curve (ROC-AUC. Results The feasibility examination indicated that accelerometer measurements of 30 toddlers (63.8% could be included with a mean registration time of 564 ± 62 min during weekdays and 595 ± 83 min during weekend days. According to the parental reports, 83% perceived wearing the accelerometer as 'not unpleasant and not pleasant' and none as 'unpleasant'. The validity evaluation showed that mean ActiGraph activity counts were significantly and positively associated with mean OSRAC-P activity intensity (r = 0.66; p Conclusions The present findings suggest that ActiGraph accelerometer measurements are feasible and valid for quantifying PA in toddlers. However, further research is needed to accurately identify PA intensities in toddlers using accelerometry.

  15. Validation of the Actical Accelerometer in Multiethnic Preschoolers: The Children's Healthy Living (CHL) Program

    OpenAIRE

    Ettienne, Reynolette; Nigg, Claudio R.; Li, Fenfang; Su, Yuhua; McGlone, Katalina; Luick, Bret; Tachibana, Alvin; Carran, Christina; Mercado, Jobel; Novotny, Rachel

    2016-01-01

    This study aimed to determine the validity and reliability of the Actical accelerometer for measuring physical activity (PA) in preschool children of mixed ethnicity, compared with direct observation via a modified System for Observing Fitness Instruction Time (SOFIT) protocol and proxy parental reports (PA Logs). Fifty children in Hawai‘i wore wrist-mounted accelerometers for two 7-day periods with a washout period between each week. Thirty children were concurrently observed using SOFIT. Pa...

  16. Identifying Active Travel Behaviors in Challenging Environments Using GPS, Accelerometers, and Machine Learning Algorithms

    OpenAIRE

    Ellis, Katherine; Godbole, Suneeta; Marshall, Simon; Lanckriet, Gert; Staudenmayer, John; Kerr, Jacqueline

    2014-01-01

    Background: Active travel is an important area in physical activity research, but objective measurement of active travel is still difficult. Automated methods to measure travel behaviors will improve research in this area. In this paper, we present a supervised machine learning method for transportation mode prediction from global positioning system (GPS) and accelerometer data. Methods: We collected a dataset of about 150 h of GPS and accelerometer data from two research assistants follow...

  17. Identifying active travel behaviors in challenging environments using GPS, accelerometers and machine learning algorithms

    OpenAIRE

    Katherine eEllis; Suneeta eGodbole; Simon eMarshall; Gert eLanckriet; John eStaudenmayer; Jacqueline eKerr

    2014-01-01

    Background: Active travel is an important area in physical activity research, but objective measurement of active travel is still difficult. Automated methods to measure travel behaviors will improve research in this area. In this paper we present a supervised machine learning method for transportation mode prediction from GPS and accelerometer data. Methods: We collected a dataset of about 150 hours of GPS and accelerometer data from two research assistants following a protocol of prescribe...

  18. Using accelerometers to remotely and automatically characterize behavior in small animals.

    Science.gov (United States)

    Hammond, Talisin T; Springthorpe, Dwight; Walsh, Rachel E; Berg-Kirkpatrick, Taylor

    2016-06-01

    Activity budgets in wild animals are challenging to measure via direct observation because data collection is time consuming and observer effects are potentially confounding. Although tri-axial accelerometers are increasingly employed for this purpose, their application in small-bodied animals has been limited by weight restrictions. Additionally, accelerometers engender novel complications, as a system is needed to reliably map acceleration to behaviors. In this study, we describe newly developed, tiny acceleration-logging devices (1.5-2.5 g) and use them to characterize behavior in two chipmunk species. We collected paired accelerometer readings and behavioral observations from captive individuals. We then employed techniques from machine learning to develop an automatic system for coding accelerometer readings into behavioral categories. Finally, we deployed and recovered accelerometers from free-living, wild chipmunks. This is the first time to our knowledge that accelerometers have been used to generate behavioral data for small-bodied (<100 g), free-living mammals. PMID:26994177

  19. Use of a Wireless Network of Accelerometers for Improved Measurement of Human Energy Expenditure

    Directory of Open Access Journals (Sweden)

    Alexander H. Montoye

    2014-04-01

    Full Text Available Single, hip-mounted accelerometers can provide accurate measurements of energy expenditure (EE in some settings, but are unable to accurately estimate the energy cost of many non-ambulatory activities. A multi-sensor network may be able to overcome the limitations of a single accelerometer. Thus, the purpose of our study was to compare the abilities of a wireless network of accelerometers and a hip-mounted accelerometer for the prediction of EE. Thirty adult participants engaged in 14 different sedentary, ambulatory, lifestyle and exercise activities for five minutes each while wearing a portable metabolic analyzer, a hip-mounted accelerometer (AG and a wireless network of three accelerometers (WN worn on the right wrist, thigh and ankle. Artificial neural networks (ANNs were created separately for the AG and WN for the EE prediction. Pearson correlations (r and the root mean square error (RMSE were calculated to compare criterion-measured EE to predicted EE from the ANNs. Overall, correlations were higher (r = 0.95 vs. r = 0.88, p < 0.0001 and RMSE was lower (1.34 vs. 1.97 metabolic equivalents (METs, p < 0.0001 for the WN than the AG. In conclusion, the WN outperformed the AG for measuring EE, providing evidence that the WN can provide highly accurate estimates of EE in adults participating in a wide range of activities.

  20. Linearity enhancement of scale factor in an optical interrogated micromechanical accelerometer.

    Science.gov (United States)

    Zhang, Yu; Feng, Lishuang; Wang, Xiao; Wang, Yang

    2016-08-01

    A method to reduce the residual stress of support arms in an optical interrogated micromechanical accelerometer is proposed in order to enhance the linearity of the scale factor of the accelerometer. First, the behavior of residual stress in support arms is analyzed in detail, and the simulation of shape curvature caused by residual stress in aluminum-made support arms is completed using finite element analysis. Then, by comparing two different materials of support arms (aluminum-made and silicon-made support arms), a modified fabrication is introduced in order to reduce the unexpected residual stress in support arms. Finally, based on contrast experiments, the linearity of the scale factor of accelerometers with aluminum-made and silicon-made support arms is measured using the force feedback test system, respectively. Results show that the linearity of the scale factor of the accelerometer with silicon-made support arms is 0.85%, which is reduced about an order of magnitude compared to that of the accelerometer with aluminum-made support arms with the linearity of scale factor of 7.48%; linearity enhancement of the scale factor is validated. This allows accuracy improvement of the optical interrogated micromechanical accelerometer in the application of inertial navigation and positioning. PMID:27505396

  1. Performance of a single reflective grating-based fiber optic accelerometer

    Science.gov (United States)

    Lee, Yeon-Gwan; Kim, Dae-Hyun; Kim, Chun-Gon

    2012-04-01

    This paper presents a single reflective grating-based fiber optic accelerometer that can monitor the low-frequency acceleration of civil engineering structures. A simpler sensor structure was realized by employing a single reflective grating panel and two optical fibers as transceivers rather than the moiré fringe fiber optic accelerometer, which is composed of two gratings and four optical fibers. The simplified layout contributes to resolving the issues of space restraints during installation and complex cabling problems in transmission of fiber optic accelerometers. The measured oscillated displacement and sinusoidal acceleration from the proposed fiber optic sensor demonstrated good agreement with those of a commercial laser displacement sensor and an accelerometer without electromagnetic interference. The developed fiber optic accelerometer can be used in frequency ranges below 4 Hz within a 5% error margin and high sensitivity of 33.33 rad G-1. Furthermore, in comparison with the conventional transmission fiber optic accelerometer design, the proposed scheme's cable design is simplified by 50%.

  2. Synthesis of the System Modeling and Signal Detecting Circuit of a Novel Vacuum Microelectronic Accelerometer

    Directory of Open Access Journals (Sweden)

    Zhengguo Shang

    2009-05-01

    Full Text Available A novel high-precision vacuum microelectronic accelerometer has been successfully fabricated and tested in our laboratory. This accelerometer has unique advantages of high sensitivity, fast response, and anti-radiation stability. It is a prototype intended for navigation applications and is required to feature micro-g resolution. This paper briefly describes the structure and working principle of our vacuum microelectronic accelerometer, and the mathematical model is also established. The performances of the accelerometer system are discussed after Matlab modeling. The results show that, the dynamic response of the accelerometer system is significantly improved by choosing appropriate parameters of signal detecting circuit, and the signal detecting circuit is designed. In order to attain good linearity and performance, the closed-loop control mode is adopted. Weak current detection technology is studied, and integral T-style feedback network is used in I/V conversion, which will eliminate high-frequency noise at the front of the circuit. According to the modeling parameters, the low-pass filter is designed. This circuit is simple, reliable, and has high precision. Experiments are done and the results show that the vacuum microelectronic accelerometer exhibits good linearity over -1 g to +1 g, an output sensitivity of 543 mV/g, and a nonlinearity of 0.94 %.

  3. Applications of ISA accelerometer for the exploration of the Moon

    Science.gov (United States)

    Iafolla, Valerio; Peron, Roberto; Nozzoli, Sergio; Santoli, Francesco; Fiorenza, Emiliano; Lefevre, Carlo; Reale, Andrea

    The recent years have seen again the Moon as a target for exploration activities. The reasons for this new wave are manifold, from the knowledge of formation and evolution of the Moon towards its current state to the possibility of building a human settlement on its surface, with all the related issues of environment characterization, safety, resources, communication and navigation. Our natural satellite is also an important laboratory for fundamental physics: Lunar Laser Ranging is continuing to provide important data that constrain possible theories of gravitation. ISA (Italian Spring Accelerometer) can provide an important tool in this respect. Thanks to its concept it works both in-orbit and on-ground, with essentially the same configuration. It therefore can be used onboard a spacecraft, as a support to a radio science mission, and on the surface of the Moon, as a seismometer. Two options have been considered. The first one is the support to space gravimetric measurements to be performed in the context of the proposed MAGIA (Missione Altimetrica Gravimetrica geochImica lunAre) mission. The second one concerns ISA as a candidate seismometer to be hosted on NASA ILN (International Lunar Network) and ESA First Lunar Lander. Both options will be discussed, giving emphasis on the integration of the instrument in the overall mission scenarios.

  4. Micromachined silicon cantilever beam accelerometer incorporating an integrated optical waveguide

    Science.gov (United States)

    Burcham, Kevin E.; De Brabander, Gregory N.; Boyd, Joseph T.

    1993-01-01

    A micromachined cantilever beam accelerometer is described in which beam deflection is determined optically. A diving board structure is anisotropically etched into a silicon wafer. This diving board structure is patterned from the wafer backside so as to leave a small gap between the tip of the diving board and the opposite fixed edge on the front side of the wafer. In order to sense a realistic range of accelerations, a foot mass incorporated onto the end of the beam is found to provide design flexibility. A silicon nitride optical waveguide is then deposited by low pressure chemical vapor deposition (LPCVD) onto the sample. Beam deflection is measured by the decrease of light coupled across the gap between the waveguide sections. In order to investigate sensor response and simulate deflection of the beam, we utilized a separate beam and waveguide section which could be displaced from one another in a precisely controlled manner. Measurements were performed on samples with gaps of 4.0, 6.0, and 8.0 micron and the variation of the fraction of light coupled across the gap as a function of displacement and gap spacing was found to agree with overlap integral calculations.

  5. BepiColombo ISA accelerometer: ready for launch

    Science.gov (United States)

    Francesco, Santoli; Valerio, Iafolla; Emiliano, Fiorenza; Carlo, Lefevre; Lucchesi David, M.; Marco, Lucente; Carmelo, Magnafico; Sergio, Nozzoli; Roberto, Peron

    2016-04-01

    To be launched in 2017, ESA mission BepiColombo will perform a thorough study of the planet Mercury and its environment. Among the wide range of its scientific objectives, an important set is constituted by the so-called Radio Science Experiments (RSE), which will study the gravitational field and rotation of the planet, and will perform very precise tests of general relativity theory. The fulfilment of these scientific objectives will be made possible by a precise orbit determination of the Mercury Planetary Orbiter (MPO), at the same time estimating a number of relevant parameters. In order to reach the required level of accuracy in recovering these parameters, the data coming from the high-sensitivity ISA (Italian Spring Accelerometer) instrument onboard the MPO probe will be used: the first time for a deep-space probe. After a long path of design and development, the instrument is now ready for integration into MPO. Following a brief description of the RSE in the context of the mission, the instrument and its capabilities will be reviewed. Emphasis will be given to the foreseen strategies for its operation in the various phases of the mission, along with the manifold calibration possibilities.

  6. Movement prediction using accelerometers in a human population.

    Science.gov (United States)

    Xiao, Luo; He, Bing; Koster, Annemarie; Caserotti, Paolo; Lange-Maia, Brittney; Glynn, Nancy W; Harris, Tamara B; Crainiceanu, Ciprian M

    2016-06-01

    We introduce statistical methods for predicting the types of human activity at sub-second resolution using triaxial accelerometry data. The major innovation is that we use labeled activity data from some subjects to predict the activity labels of other subjects. To achieve this, we normalize the data across subjects by matching the standing up and lying down portions of triaxial accelerometry data. This is necessary to account for differences between the variability in the position of the device relative to gravity, which are induced by body shape and size as well as by the ambiguous definition of device placement. We also normalize the data at the device level to ensure that the magnitude of the signal at rest is similar across devices. After normalization we use overlapping movelets (segments of triaxial accelerometry time series) extracted from some of the subjects to predict the movement type of the other subjects. The problem was motivated by and is applied to a laboratory study of 20 older participants who performed different activities while wearing accelerometers at the hip. Prediction results based on other people's labeled dictionaries of activity performed almost as well as those obtained using their own labeled dictionaries. These findings indicate that prediction of activity types for data collected during natural activities of daily living may actually be possible. PMID:26288278

  7. On-Body Smartphone Localization with an Accelerometer

    Directory of Open Access Journals (Sweden)

    Kaori Fujinami

    2016-03-01

    Full Text Available A user of a smartphone may feel convenient, happy, safe, etc., if his/her smartphone works smartly based on his/her context or the context of the device. In this article, we deal with the position of a smartphone on the body and carrying items like bags as the context of a device. The storing position of a smartphone impacts the performance of the notification to a user, as well as the measurement of embedded sensors, which plays an important role in a device’s functionality control, accurate activity recognition and reliable environmental sensing. In this article, nine storing positions, including four types of bags, are subject to recognition using an accelerometer on a smartphone. In total, 63 features are selected as a set of features among 182 systematically-defined features, which can characterize and discriminate the motion of a smartphone terminal during walking. As a result of leave-one-subject-out cross-validation, an accuracy of 0.801 for the nine-class classification is shown, while an accuracy of 0.859 is obtained against five classes, which merges the subclasses of trouser pockets and bags. We also show the basic performance evaluation to select the proper window size and classifier. Furthermore, the analysis of the contributive features is presented.

  8. Optimising Performance of a Cantilever-type Micro Accelerometer Sensor

    Directory of Open Access Journals (Sweden)

    B.P. Joshi

    2007-05-01

    Full Text Available A technique for optimising performance of cantilever-type micro acceleration sensor hasbeen developed. Performance of a sensor is judged mainly by its sensitivity and bandwidth.Maximising product of these two important parameters of inertial sensors helps to optimise thesensor performance. It is observed that placement of a lumped mass (add-mass on the sensor'sproof-mass helps to control both sensitivity and the first resonant frequency of the cantileverstructure to the designer's choice. Simulation and modelling of various dimensions of rectangularstructures for acceleration sensor with this novel add-mass technique are discussed. CoventorwareMEMSCAD has been used to model, simulate, and carry out FEM analysis. A simple analyticalmodel is discussed to elaborate the mechanics of cantilever-type micro accelerometer. Thecomparison of the results obtained from analytical model and the finite element simulations revealthese to be in good agreement. The advantages of this technique for choosing the two mostimportant sensor parameters (i.e., sensitivity and bandwidth of an inertial sensor are brought out.

  9. Detection of rail corrugation based on fiber laser accelerometers

    Science.gov (United States)

    Huang, Wenzhu; Zhang, Wentao; Du, Yanliang; Sun, Baochen; Ma, Huaixiang; Li, Fang

    2013-09-01

    Efficient inspection methods are necessary for detection of rail corrugation to improve the safety and ride quality of railway operations. This paper presents a novel fiber optic technology for detection of rail corrugation based on fiber laser accelerometers (FLAs), tailored to the measurement of surface damage on rail structures. The principle of detection of rail corrugation using double integration of axle-box acceleration is presented. Then we present the theoretical model and test results of FLAs which are installed on the bogie to detect the vertical axle-box acceleration of the train. Characteristics of high sensitivity and large dynamic range are achieved when using fiber optic interferometric demodulation. A flexible inertial algorithm based on double integration and the wavelet denoising method is proposed to accurately estimate the rail corrugation. A field test is carried out on the Datong-Qinhuangdao Railway in north China. The test results are compared with the results of a rail inspection car, which shows that the fiber laser sensing system has a good performance in monitoring rail corrugation.

  10. Reliability issues of an accelerometer under environmental stresses

    Science.gov (United States)

    Schmitt, Petra; Pressecq, Francis; Perez, Guy; Lafontan, Xavier; Nicot, Jean Marc; Esteve, Daniel; Fourniols, Jean Yves; Camon, Henri; Oudea, Coumar

    2004-01-01

    COTS (Commercial-off-the-shelf) MEMS components are very interesting for space applications because they are lightweight, small, economic in energy, cheap and available in short delays. The reliability of MEMS COTS that are used out of their intended domain of operation (such as a space application) might be assured by a reliability methodology derived from the Physics of Failure approach. In order to use this approach it is necessary to create models of MEMS components that take into consideration environmental stresses and thus can be used for lifetime prediction. Unfortunately, today MEMS failure mechanisms are not well understood today and therefore a preliminary work is necessary to determine influent factors and physical phenomena. The model development is based on a good knowledge of the process parameters (Young"s modulus, stress...), environmental tests and appropriated modeling approaches, such a finite element analysis (FEA) and behavioural modeling. In order to do the environmental tests and to analyse MEMS behaviour, we have developed the Environmental MEMS Analyzer EMA 3D. The described methodology has been applied to a Commercial-off-the-shelf (COTS) accelerometer, the ADXL150. A first level behavioral model was created and then refined in the following steps by the enrichment with experimental results and finite element simulations.

  11. Classification of knee arthropathy with accelerometer-based vibroarthrography.

    Science.gov (United States)

    Moreira, Dinis; Silva, Joana; Correia, Miguel V; Massada, Marta

    2016-01-01

    One of the most common knee joint disorders is known as osteoarthritis which results from the progressive degeneration of cartilage and subchondral bone over time, affecting essentially elderly adults. Current evaluation techniques are either complex, expensive, invasive or simply fails into detection of small and progressive changes that occur within the knee. Vibroarthrography appeared as a new solution where the mechanical vibratory signals arising from the knee are recorded recurring only to an accelerometer and posteriorly analyzed enabling the differentiation between a healthy and an arthritic joint. In this study, a vibration-based classification system was created using a dataset with 92 healthy and 120 arthritic segments of knee joint signals collected from 19 healthy and 20 arthritic volunteers, evaluated with k-nearest neighbors and support vector machine classifiers. The best classification was obtained using the k-nearest neighbors classifier with only 6 time-frequency features with an overall accuracy of 89.8% and with a precision, recall and f-measure of 88.3%, 92.4% and 90.1%, respectively. Preliminary results showed that vibroarthrography can be a promising, non-invasive and low cost tool that could be used for screening purposes. Despite this encouraging results, several upgrades in the data collection process and analysis can be further implemented.

  12. Motion analysis of sun salutation using magnetometer and accelerometer

    Directory of Open Access Journals (Sweden)

    Omkar S

    2009-01-01

    Full Text Available Background: Sun salutation is a part of yoga. It consists of a sequence of postures done with synchronized breathing. The practice of few cycles of sun salutation is known to help in maintaining good health and vigor. The practice of sun salutation does not need any extra gadgets. Also it is very much aerobic and invigorates the body and the mind. sun salutation, which comprises 10 postures, involves most of the joints of the body. Understanding the transition phase during motion is a challenging task, and thus, new convenient methods need to be employed. Aims: The purpose of this study was to get an insight into the motion analysis of sun salutation during the transition from each of the 10 postures. Materials and Methods: A device MicroStrain sensor 3DM-GX1, which is a combination of magnetometers, accelerometers, and gyroscopes was used to measure the inclination and the acceleration of the body along the three axes. The acceleration obtained was then separated into gravitational and kinematic components. Results and Conclusions: The value of the gravitational component helps us to understand the position of the body and the kinematic component helps us to analyze the grace of the motion.

  13. Can accelerometers detect mass variations in Amazonian trees?

    Science.gov (United States)

    van Emmerik, Tim; Steele-Dunne, Susan; Gentine, Pierre; Guerin, Marceau; Hut, Rolf; Oliveira, Rafael; van de Giesen, Nick

    2016-04-01

    The mass of trees is influenced by physiological processes within the tree (e.g. transpiration and root water uptake), as well as external loads (e.g. intercepted precipitation). Recent studies have found diurnal variations in radar backscatter over vegetated areas, which might be attributed to mass changes of the vegetation layer. Field measurements are required to study the driving processes. This study aims to use measured three-dimensional displacement and acceleration of trees, to detect and quantify their diurnal (bio)mass variations. Accelerometers and dendrometers were installed on seven different tree species in the Amazon rainforest. Trees were selected to cover a broad range of wood density. Using spectral analysis, the governing frequencies in the acceleration time series were found. The governing frequencies showed a diurnal pattern, as well as a change during precipitation events. Our results suggest that we can separate and potentially quantify tree mass changes due to (1) internal water redistribution and (2) intercepted precipitation. This will allow further investigation of the effect of precipitation and water stress on tree dynamics in forest canopies.

  14. Separating bedtime rest from activity using waist or wrist-worn accelerometers in youth.

    Directory of Open Access Journals (Sweden)

    Dustin J Tracy

    Full Text Available Recent interest in sedentary behavior and technological advances expanded use of watch-size accelerometers for continuous monitoring of physical activity (PA over extended periods (e.g., 24 h/day for 1 week in studies conducted in natural living environment. This approach necessitates the development of new methods separating bedtime rest and activity periods from the accelerometer recordings. The goal of this study was to develop a decision tree with acceptable accuracy for separating bedtime rest from activity in youth using accelerometer placed on waist or wrist. Minute-by-minute accelerometry data were collected from 81 youth (10-18 years old, 47 females during a monitored 24-h stay in a whole-room indirect calorimeter equipped with a force platform covering the floor to detect movement. Receiver Operating Characteristic (ROC curve analysis was used to determine the accelerometer cut points for rest and activity. To examine the classification differences, the accelerometer bedtime rest and activity classified by the algorithm in the development group (n = 41 were compared with actual bedtime rest and activity classification obtained from the room calorimeter-measured metabolic rate and movement data. The selected optimal bedtime rest cut points were 20 and 250 counts/min for the waist- and the wrist-worn accelerometer, respectively. The selected optimal activity cut points were 500 and 3,000 counts/min for waist and wrist-worn accelerometers, respectively. Bedtime rest and activity were correctly classified by the algorithm in the validation group (n = 40 by both waist- (sensitivity: 0.983, specificity: 0.946, area under ROC curve: 0. 872 and wrist-worn (0.999, 0.980 and 0.943 accelerometers. The decision tree classified bedtime rest correctly with higher accuracy than commonly used automated algorithm for both waist- and wrist-warn accelerometer (all p<0.001. We concluded that cut points developed and validated for waist- and wrist

  15. Validation of a novel smartphone accelerometer-based knee goniometer.

    Science.gov (United States)

    Ockendon, Matthew; Gilbert, Robin E

    2012-09-01

    Loss of full knee extension following anterior cruciate ligament surgery has been shown to impair knee function. However, there can be significant difficulties in accurately and reproducibly measuring a fixed flexion of the knee. We studied the interobserver and the intraobserver reliabilities of a novel, smartphone accelerometer-based, knee goniometer and compared it with a long-armed conventional goniometer for the assessment of fixed flexion knee deformity. Five healthy male volunteers (age range 30 to 40 years) were studied. Measurements of knee flexion angle were made with a telescopic-armed goniometer (Lafayette Instrument, Lafayette, IN) and compared with measurements using the smartphone (iPhone 3GS, Apple Inc., Cupertino, CA) knee goniometer using a novel trigonometric technique based on tibial inclination. Bland-Altman analysis of validity and reliability including statistical analysis of correlation by Pearson's method was undertaken. The iPhone goniometer had an interobserver correlation (r) of 0.994 compared with 0.952 for the Lafayette. The intraobserver correlation was r = 0.982 for the iPhone (compared with 0.927). The datasets from the two instruments correlate closely (r = 0.947) are proportional and have mean difference of only -0.4 degrees (SD 3.86 degrees). The Lafayette goniometer had an intraobserver reliability +/- 9.6 degrees. The interobserver reliability was +/- 8.4 degrees. By comparison the iPhone had an interobserver reliability +/- 2.7 degrees and an intraobserver reliability +/- 4.6 degrees. We found the iPhone goniometer to be a reliable tool for the measurement of subtle knee flexion in the clinic setting. PMID:23150162

  16. Self Diagnostic Accelerometer Ground Testing on a C-17 Aircraft Engine

    Science.gov (United States)

    Tokars, Roger P.; Lekki, John D.

    2013-01-01

    The self diagnostic accelerometer (SDA) developed by the NASA Glenn Research Center was tested for the first time in an aircraft engine environment as part of the Vehicle Integrated Propulsion Research (VIPR) program. The VIPR program includes testing multiple critical flight sensor technologies. One such sensor, the accelerometer, measures vibrations to detect faults in the engine. In order to rely upon the accelerometer, the health of the accelerometer must be ensured. Sensor system malfunction is a significant contributor to propulsion in flight shutdowns (IFSD) which can lead to aircraft accidents when the issue is compounded with an inappropriate crew response. The development of the SDA is important for both reducing the IFSD rate, and hence reducing the rate at which this component failure type can put an aircraft in jeopardy, and also as a critical enabling technology for future automated malfunction diagnostic systems. The SDA is a sensor system designed to actively determine the accelerometer structural health and attachment condition, in addition to making vibration measurements. The SDA uses a signal conditioning unit that sends an electrical chirp to the accelerometer and recognizes changes in the response due to changes in the accelerometer health and attachment condition. In an effort toward demonstrating the SDAs flight worthiness and robustness, multiple SDAs were mounted and tested on a C-17 aircraft engine. The engine test conditions varied from engine off, to idle, to maximum power. The two SDA attachment conditions used were fully tight and loose. The newly developed SDA health algorithm described herein uses cross correlation pattern recognition to discriminate a healthy from a faulty SDA. The VIPR test results demonstrate for the first time the robustness of the SDA in an engine environment characterized by high vibration levels.

  17. Temperature insensitive all-fiber accelerometer using a photonic crystal fiber long-period grating interferometer

    Science.gov (United States)

    Zheng, Shijie; Zhu, Yinian; Krishnaswamy, Sridhar

    2012-04-01

    Fiber-optic accelerometers have attracted great attention in recent years due to the fact that they have many advantages over electrical counterparts because all-fiber accelerometers have the capabilities for multiplexing to reduce cabling and to transmit signals over a long distance. They are also immune to electromagnetic interference. We propose and develop a compact and robust photonic crystal fiber (PCF) Mach-Zehnder interferometer (MZI) that can be implemented as an accelerometer for measurements of vibration and displacement. To excite core mode to couple out with cladding modes, two long-period gratings (LPGs) with identical transmission spectra are needed to be written in an endless single-mode PCF using a CO2 laser. The first LPG can couple a part of core mode to several cladding modes. After the light beams travel at different speeds over a certain length of the core and cladding, the cladding modes will be recoupled back to the core when they meet the second LPG, resulting in interference between the core mode and cladding modes. Dynamic strain is introduced to the PCF-MZI fiber segment that is bonded onto a spring-mass system. The shift of interference fringe can be measured by a photodetector, and the transformed analog voltage signal is proportional to the acceleration of the sensor head. Based on simulations of the PCF-MZI accelerometer, we can get a sensitivity of ~ 0.08 nm/g which is comparable with fiber Bragg grating (FBG) accelerometers. The proposed accelerometer has a capability of temperature insensitivity; therefore, no thermal-compensation scheme is required. Experimental results indicate that the PCF-MZI accelerometer may be a good candidate sensor for applications in civil engineering infrastructure and aeronautical platforms.

  18. Does a waist-worn ActiGraph accelerometer quantify community ambulation in persons with multiple sclerosis?

    OpenAIRE

    Jacob J. Sosnoff, PhD; Michael J. Socie, MS; Morgan K. Boes, MS; Brian M. Sandroff, MS; Robert W. Motl, PhD

    2012-01-01

    Accelerometry has been recognized as a method of objectively measuring community ambulation in persons with multiple sclerosis (MS). However, the assumption that walking itself serves as a major contributor to the accelerometer signal has yet to be tested. This study examined the assumption that community-based walking is a primary contributor to accelerometer output in MS. Ambulatory persons (5 males/17 females; 13 without aid/9 with aid) with MS wore a triaxial accelerometer (ActiGraph GT3X...

  19. Pyroshock data acquisition-recent developments using P/R and P/E accelerometers and isolators

    Science.gov (United States)

    Bateman, Vesta I.

    2002-05-01

    Mechanical isolators have been developed for piezoresistive and piezoelectric accelerometers to mitigate high frequency shocks before they reach the accelerometer because the high frequency pyroshocks may cause the accelerometer to resonate and/or break. Several commercial mechanically isolated accelerometers are available to the general public and their characteristics have been studied using Hopkinson bar test techniques. The in-axis response of these devices will be compared. Cross-axis response will be presented for one device. Additionally, pyroshock and ballistic shock measurements, performed by international organizations, will be presented for several isolators.

  20. Utility of Accelerometers to Measure Physical Activity in Children Attending an Obesity Treatment Intervention

    Directory of Open Access Journals (Sweden)

    Wendy Robertson

    2011-01-01

    Full Text Available Objectives. To investigate the use of accelerometers to monitor change in physical activity in a childhood obesity treatment intervention. Methods. 28 children aged 7–13 taking part in “Families for Health” were asked to wear an accelerometer (Actigraph for 7-days, and complete an accompanying activity diary, at baseline, 3-months and 9-months. Interviews with 12 parents asked about research measurements. Results. Over 90% of children provided 4 days of accelerometer data, and around half of children provided 7 days. Adequately completed diaries were collected from 60% of children. Children partake in a wide range of physical activity which uniaxial monitors may undermonitor (cycling, nonmotorised scootering or overmonitor (trampolining. Two different cutoffs (4 METS or 3200 counts⋅min-1 for minutes spent in moderate and vigorous physical activity (MVPA yielded very different results, although reached the same conclusion regarding a lack of change in MVPA after the intervention. Some children were unwilling to wear accelerometers at school and during sport because they felt they put them at risk of stigma and bullying. Conclusion. Accelerometers are acceptable to a majority of children, although their use at school is problematic for some, but they may underestimate children's physical activity.

  1. Evaluation of MEMS-Based Wireless Accelerometer Sensors in Detecting Gear Tooth Faults in Helicopter Transmissions

    Science.gov (United States)

    Lewicki, David George; Lambert, Nicholas A.; Wagoner, Robert S.

    2015-01-01

    The diagnostics capability of micro-electro-mechanical systems (MEMS) based rotating accelerometer sensors in detecting gear tooth crack failures in helicopter main-rotor transmissions was evaluated. MEMS sensors were installed on a pre-notched OH-58C spiral-bevel pinion gear. Endurance tests were performed and the gear was run to tooth fracture failure. Results from the MEMS sensor were compared to conventional accelerometers mounted on the transmission housing. Most of the four stationary accelerometers mounted on the gear box housing and most of the CI's used gave indications of failure at the end of the test. The MEMS system performed well and lasted the entire test. All MEMS accelerometers gave an indication of failure at the end of the test. The MEMS systems performed as well, if not better, than the stationary accelerometers mounted on the gear box housing with regards to gear tooth fault detection. For both the MEMS sensors and stationary sensors, the fault detection time was not much sooner than the actual tooth fracture time. The MEMS sensor spectrum data showed large first order shaft frequency sidebands due to the measurement rotating frame of reference. The method of constructing a pseudo tach signal from periodic characteristics of the vibration data was successful in deriving a TSA signal without an actual tach and proved as an effective way to improve fault detection for the MEMS.

  2. The timing of scour and fill in a gravel-bedded river measured with buried accelerometers

    Science.gov (United States)

    Gendaszek, Andrew S.; Magirl, Christopher S.; Czuba, Christiana R.; Konrad, Christopher P.

    2013-01-01

    A device that measures the timing of streambed scour and the duration of sediment mobilization at specific depths of a streambed was developed using data-logging accelerometers placed within the gravel substrate of the Cedar River, Washington, USA. Each accelerometer recorded its orientation every 20 min and remained stable until the surrounding gravel matrix mobilized as sediment was transported downstream and scour reached the level of the accelerometer. The accelerometer scour monitors were deployed at 26 locations in salmon-spawning habitat during the 2010–2011 flood season to record when the streambed was scoured to the depth of typical egg-pocket deposition. Scour was recorded at one location during a moderate high-flow event (65 m3/s; 1.25–1.5-year recurrence interval) and at 17 locations during a larger high-flow event (159 m3/s; 7-year recurrence interval). Accelerometer scour monitors recorded periods of intermittent sediment mobilization and stability within a high-flow event providing insight into the duration of scour. Most scour was recorded during the rising limb and at the peak of a flood hydrograph, though some scour occurred during sustained high flows following the peak of the flood hydrograph.

  3. Noise behaviors of a closed-loop micro-electromechanical system capacitive accelerometer

    Institute of Scientific and Technical Information of China (English)

    马铭骏; 金仲和; 刘义冬; 马铁英

    2015-01-01

    The noise of closed loop micro-electromechanical systems (MEMS) capacitive accelerometer is treated as one of the significant performance specifications. Traditional optimization of noise performance often focuses on designing large capacitive sensitivity accelerometer and applying closed loop structure to shape total noise, but different noise sources in closed loop and their behaviors at low frequencies are seldom carefully studied, especially their behaviors with different electronic parameters. In this work, a thorough noise analysis is established focusing on the four noise sources transfer functions near 0 Hz with simplified electronic parameters in closed loop, and it is found that the total electronic noise equivalent acceleration varies differently at different frequency points, such that the noise spectrum shape at low frequencies can be altered from 1/f noise-like shape to flat spectrum shape. The bias instability changes as a consequence. With appropriate parameters settings, the 670 Hz resonant frequency accelerometer can reach resolution of 2.6μg/Hz at 2 Hz and 6 µg bias instability, and 1300 Hz accelerometer can achieve 5μg/Hz at 2 Hz and 31 µg bias instability. Both accelerometers have flat spectrum profile from 2 Hz to 15 Hz.

  4. Feasibility of frequency-modulated wireless transmission for a multi-purpose MEMS-based accelerometer.

    Science.gov (United States)

    Sabato, Alessandro; Feng, Maria Q

    2014-09-05

    Recent advances in the Micro Electro-Mechanical System (MEMS) technology have made wireless MEMS accelerometers an attractive tool for Structural Health Monitoring (SHM) of civil engineering structures. To date, sensors' low sensitivity and accuracy--especially at very low frequencies--have imposed serious limitations for their application in monitoring large-sized structures. Conventionally, the MEMS sensor's analog signals are converted to digital signals before radio-frequency (RF) wireless transmission. The conversion can cause a low sensitivity to the important low-frequency and low-amplitude signals. To overcome this difficulty, the authors have developed a MEMS accelerometer system, which converts the sensor output voltage to a frequency-modulated signal before RF transmission. This is achieved by using a Voltage to Frequency Conversion (V/F) instead of the conventional Analog to Digital Conversion (ADC). In this paper, a prototype MEMS accelerometer system is presented, which consists of a transmitter and receiver circuit boards. The former is equipped with a MEMS accelerometer, a V/F converter and a wireless RF transmitter, while the latter contains an RF receiver and a F/V converter for demodulating the signal. The efficacy of the MEMS accelerometer system in measuring low-frequency and low-amplitude dynamic responses is demonstrated through extensive laboratory tests and experiments on a flow-loop pipeline.

  5. A novel sandwich capacitive accelerometer with a symmetrical structure fabricated from a D-SOI wafer

    International Nuclear Information System (INIS)

    This paper presents a novel sandwich capacitance accelerometer with a symmetrical double-sided beam-mass structure. The symmetrical beam-mass structure is fabricated from a double-device-layer silicon-on-insulate (D-SOI) wafer. The proof mass is suspended by eight beams at the corners on both sides. The beams are fabricated at the device layers of the SOI wafer; the cross-section of the beams is a standard trapezoid. The thickness of the beams can be well controlled because it is determined by the thickness of the device layer in the SOI wafer, and there is no dry etching process in the accelerometer fabrication. The resonance frequency of the developed accelerometer is measured in an open-loop system by a network analyzer. The quality factor and the resonant frequency are 18 and 812 Hz, respectively. The accelerometer has an opened-loop capacitance sensitivity of 8.7 pF g−1, a closed-loop sensitivity of 1.39 V g−1 and a nonlinearity of 0.49% over the range of 1 g. The measured input, referred to as the noise floor of the accelerometers, with an interface circuit is 2.4 µg (√Hz)−1 (0–100 Hz). (paper)

  6. A novel micro-accelerometer with adjustable sensitivity based on resonant tunnelling diodes

    International Nuclear Information System (INIS)

    Resonant tunnelling diodes (RTDs) have negative differential resistance effect, and the current-voltage characteristics change as a function of external stress, which is regarded as meso-piezoresistance effect of RTDs. In this paper, a novel micro-accelerometer based on AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs RTDs is designed and fabricated to be a four-beam-mass structure, and an RTD-Wheatstone bridge measurement system is established to test the basic properties of this novel accelerometer. According to the experimental results, the sensitivity of the RTD based micro-accelerometer is adjustable within a range of 3 orders when the bias voltage of the sensor changes. The largest sensitivity of this RTD based micro-accelerometer is 560.2025 mV/g which is about 10 times larger than that of silicon based micro piezoresistive accelerometer, while the smallest one is 1.49135 mV/g. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  7. Measurement Method of Magnetic Field for the Wire Suspended Micro-Pendulum Accelerometer

    Directory of Open Access Journals (Sweden)

    Yongle Lu

    2015-04-01

    Full Text Available Force producer is one of the core components of a Wire Suspended Micro-Pendulum Accelerometer; and the stability of permanent magnet in the force producer determines the consistency of the acceleration sensor’s scale factor. For an assembled accelerometer; direct measurement of magnetic field strength is not a feasible option; as the magnetometer probe cannot be laid inside the micro-space of the sensor. This paper proposed an indirect measurement method of the remnant magnetization of Micro-Pendulum Accelerometer. The measurement is based on the working principle of the accelerometer; using the current output at several different scenarios to resolve the remnant magnetization of the permanent magnet. Iterative Least Squares algorithm was used for the adjustment of the data due to nonlinearity of this problem. The calculated remnant magnetization was 1.035 T. Compared to the true value; the error was less than 0.001 T. The proposed method provides an effective theoretical guidance for measuring the magnetic field of the Wire Suspended Micro-Pendulum Accelerometer; correcting the scale factor and temperature influence coefficients; etc.

  8. Characteristics of a piezoresistive accelerometer in high frequency, high shock environments

    Energy Technology Data Exchange (ETDEWEB)

    Bateman, V.I.; Davie, N.T.; Brown, F.A.

    1993-12-31

    The characteristics of a piezoresistive accelerometer in shock environments are being studied at Sandia National Laboratories in the Mechanical Shock Testing Laboratory. A Hopkinson bar capability has been developed to extend our understanding of the piezoresistive accelerometer with and without mechanical isolation in the high frequency, high shock environments where measurements are being made. Two different Hopkinson bar materials are being used: titanium and beryllium. The characteristics of the piezoresistive accelerometer for frequencies of DC-10 kHz and shock magnitudes of up to 4,000 g as determined from measurements with a titanium Hopkinson bar are presented. The SNL uniaxial shock isolation technique has demonstrated acceptable characteristics for a temperature range of {minus}50{degree}F to +186{degree}F and a frequency bandwidth of DC to 10 kHz. These characteristics have been verified by the calibration of the Hopkinson bar used for accelerometer testing. The beryllium Hopkinson bar configuration is described. Preliminary characteristics of the piezoresistive accelerometer at a nominal shock level of 17,000 g for a frequency range of DC-50 kHz are presented.

  9. A novel micro-accelerometer with adjustable sensitivity based on resonant tunnelling diodes

    Institute of Scientific and Technical Information of China (English)

    Xiong Ji-Jun; Mao Hai-Yang; Zhang Wen-Dong; Wang Kai-Qun

    2009-01-01

    Resonant tunnelling diodes (RTDs) have negative differential resistance effect, and the current-voltage charac-teristics change as a function of external stress, which is regarded as meso-piezoresistance effect of RTDs. In this paper, a novel micro-accelerometer based on AlAs/GaAs/Ino.1Gao.9As/GaAs/AlAs RTDs is designed and fabricated to be a four-beam-mass structure, and an RTD-Wheatstone bridge measurement system is established to test the ba-sic properties of this novel accelerometer. According to the experimental results, the sensitivity of the RTD based micro-accelerometer is adjustable within a range of 3 orders when the bias voltage of the sensor changes. The largest sensitivity of this RTD based micro-accelerometer is 560.2025 mV/g which is about 10 times larger than that of silicon based micro piezoresistive accelerometer, while the smallest one is 1.49135 mV/g.

  10. Ground Based Investigation of Electrostatic Accelerometer in HUST

    Science.gov (United States)

    Bai, Y.; Zhou, Z.

    2013-12-01

    High-precision electrostatic accelerometers with six degrees of freedom (DOF) acceleration measurement were successfully used in CHAMP, GRACE and GOCE missions which to measure the Earth's gravity field. In our group, space inertial sensor based on the capacitance transducer and electrostatic control technique has been investigated for test of equivalence principle (TEPO), searching non-Newtonian force in micrometer range, and satellite Earth's field recovery. The significant techniques of capacitive position sensor with the noise level at 2×10-7pF/Hz1/2 and the μV/Hz1/2 level electrostatic actuator are carried out and all the six servo loop controls by using a discrete PID algorithm are realized in a FPGA device. For testing on ground, in order to compensate one g earth's gravity, the fiber torsion pendulum facility is adopt to measure the parameters of the electrostatic controlled inertial sensor such as the resolution, and the electrostatic stiffness, the cross couple between different DOFs. A short distance and a simple double capsule equipment the valid duration about 0.5 second is set up in our lab for the free fall tests of the engineering model which can directly verify the function of six DOF control. Meanwhile, high voltage suspension method is also realized and preliminary results show that the horizontal axis of acceleration noise is about 10-8m/s2/Hz1/2 level which limited mainly by the seismic noise. Reference: [1] Fen Gao, Ze-Bing Zhou, Jun Luo, Feasibility for Testing the Equivalence Principle with Optical Readout in Space, Chin. Phys. Lett. 28(8) (2011) 080401. [2] Z. Zhu, Z. B. Zhou, L. Cai, Y. Z. Bai, J. Luo, Electrostatic gravity gradiometer design for the advanced GOCE mission, Adv. Sp. Res. 51 (2013) 2269-2276. [3] Z B Zhou, L Liu, H B Tu, Y Z Bai, J Luo, Seismic noise limit for ground-based performance measurements of an inertial sensor using a torsion balance, Class. Quantum Grav. 27 (2010) 175012. [4] H B Tu, Y Z Bai, Z B Zhou, L Liu, L

  11. Theoretical analysis and concept demonstration of a novel MOEMS accelerometer based on Raman-Nath diffraction

    Institute of Scientific and Technical Information of China (English)

    Zhang Zuwei; Wen Zhiyu; Hu Jing

    2012-01-01

    The design and simulation of a novel microoptoelectromechanical system (MOEMS) accelerometer based on Raman-Nath diffraction are presented.The device is planned to be fabricated by microelectromechanical system technology and has a different sensing principle than the other reported MOEMS accelerometers.The fundamental theories and principles of the device are discussed in detail,a 3D finite element simulation of the flexural plate wave delay line oscillator is provided,and the operation frequency around 40 MHz is calculated.Finally,a lecture experiment is performed to demonstrate the feasibility of the device.This novel accelerometer is proposed to have the advantages of high sensitivity and anti-radiation,and has great potential for various applications.

  12. Android Application to Assess Smartphone Accelerometers and Bluetooth for Real-Time Control

    Directory of Open Access Journals (Sweden)

    M. A. Nugent

    2015-03-01

    Full Text Available Modern smart phones have evolved into sophisticated embedded systems, incorporating hardware and software features that make the devices potentially useful for real-time control operations. An object-oriented Android application was developed to quantify the performance of the smartphone’s on-board linear accelerometers and bluetooth wireless module with a view to potentially transmitting accelerometer data wirelessly between bluetooth-enabled devices. A portable bluetooth library was developed which runs the bluetooth functionality of the application as an independent background service. The performance of bluetooth was tested by pinging data between 2 smartphones, measuring round-trip-time and round-trip-time variation (jitter against variations in data size, transmission distance and sources of interference. The accelerometers were tested for sampling frequency and sampling frequency jitter.

  13. Technical note: Use of accelerometers to describe gait patterns in dairy calves

    DEFF Research Database (Denmark)

    Passillé, A. M. de; Jensen, Margit Bak; Chapinal, N.;

    2010-01-01

    Developments in accelerometer technology offer new opportunities for automatic monitoring of animal behavior. Until now, commercially available accelerometers have been used to measure walking in adult cows but have failed to identify walking in calves. We described the pattern of acceleration...... of steps were counted. Accelerometer data was then analyzed for each gait. Steps could be clearly identified by changes in the acceleration in the forward and vertical axes and vector sum, but less clearly in the lateral axis. The number of steps counted using the forward axis was highly correlated...... with the number observed from the video recordings. Galloping, trotting, and walking differed significantly in the median interpeak intervals in acceleration in the forward axis and in the vector sum of the acceleration in the 2 axes. Interpeak intervals could be used to discriminate among the 3 gaits, although...

  14. PENGONTROLAN GERAK MOBILE ROBOT MENGGUNAKAN SENSOR ACCELEROMETER PADA PERANGKAT BERGERAK ANDROID

    Directory of Open Access Journals (Sweden)

    Dedy Hermanto

    2015-02-01

    Full Text Available Smartphones are mobile devices that are often use by every one. In android smarphones, embedded several sensors are use to support for android phone. One of sensors that provide on android smartphones are acceleromoter sensor, an accelerometer is used to measure the acceleration of the angle X, Y and Z. With that sensors will used to drive mobile robot movement accordance with the changes of value from accelerometer sensors. This mobile robot application communicate to smartphones using bluetooth, with this wireless technology use serial for line communication to send data value to mobile robot from smartphonnes. Application for mobile robot movement using value X and Y from accelerometer sensor get from smartphones.

  15. Cable force monitoring system of cable stayed bridges using accelerometers inside mobile smart phone

    Science.gov (United States)

    Zhao, Xuefeng; Yu, Yan; Hu, Weitong; Jiao, Dong; Han, Ruicong; Mao, Xingquan; Li, Mingchu; Ou, Jinping

    2015-03-01

    Cable force is one of the most important parameters in structural health monitoring system integrated on cable stayed bridges for safety evaluation. In this paper, one kind of cable force monitoring system scheme was proposed. Accelerometers inside mobile smart phones were utilized for the acceleration monitoring of cable vibration. Firstly, comparative tests were conducted in the lab. The test results showed that the accelerometers inside smartphones can detect the cable vibration, and then the cable force can be obtained. Furthermore, there is good agreement between the monitoring results of different kinds of accelerometers. Finally, the proposed cable force monitoring system was applied on one cable strayed bridge structure, the monitoring result verified the feasibility of the monitoring system.

  16. Application of Novel Rotation Angular Model for 3D Mouse System Based on MEMS Accelerometers

    Institute of Scientific and Technical Information of China (English)

    QIAN Li; CHEN Wen-yuan; XU Guo-ping

    2009-01-01

    A new scheme is proposed to model 3D angular motion of a revolving regular object with miniature, low-cost micro electro mechanical systems (MEMS) accelerometers (instead of gyroscope), which is employed in 3D mouse system. To sense 3D angular motion, the static property of MEMS accelerometer, sensitive to gravity acceleration, is exploited. With the three outputs of configured accelerometers, the proposed model is implemented to get the rotary motion of the rigid object. In order to validate the effectiveness of the proposed model, an input device is developed with the configuration of the scheme. Experimental results show that a simulated 3D cube can accurately track the rotation of the input device. The result indicates the feasibility and effectiveness of the proposed model in the 3D mouse system.

  17. Note: A balloon-borne accelerometer technique for measuring atmospheric turbulence

    Science.gov (United States)

    Marlton, Graeme J.; Giles Harrison, R.; Nicoll, Keri A.; Williams, Paul D.

    2015-01-01

    A weather balloon and its suspended instrument package behave like a pendulum with a moving pivot. This dynamical system is exploited here for the detection of atmospheric turbulence. By adding an accelerometer to the instrument package, the size of the swings induced by atmospheric turbulence can be measured. In test flights, strong turbulence has induced accelerations greater than 5g, where g = 9.81 m s-2. Calibration of the accelerometer data with a vertically orientated lidar has allowed eddy dissipation rate values of between 10-3 and 10-2 m2 s-3 to be derived from the accelerometer data. The novel use of a whole weather balloon and its adapted instrument package can be used as a new instrument to make standardized in situ measurements of turbulence.

  18. Minimizing cross-axis sensitivity in grating-based optomechanical accelerometers.

    Science.gov (United States)

    Lu, Qianbo; Wang, Chen; Bai, Jian; Wang, Kaiwei; Lou, Shuqi; Jiao, Xufen; Han, Dandan; Yang, Guoguang; Liu, Dong; Yang, Yongying

    2016-04-18

    Cross-axis sensitivity of single-axis optomechanical accelerometers, mainly caused by the asymmetric structural design, is an essential issue primarily for high performance applications, which has not been systematically researched. This paper investigates the generating mechanism and detrimental effects of the cross-axis sensitivity of a high resoluion single-axis optomechanical accelerometer, which is composed of a grating-based cavity and an acceleration sensing chip consisting of four crab-shaped cantilevers and a proof mass. The modified design has been proposed and a prototype setup has been built based on the model of cross-axis sensitivity in optomechanical accelerometers. The characterization of the cross-axis sensitivity of a specific optomechanical accelerometer is quantitatively discussed for both mechanical and optical components by numerical simulation and theoretical analysis in this work. The analysis indicates that the cross-axis sensitivity decreases the contrast ratio of the interference signal and the acceleration sensitivity, as well as giving rise to an additional optical path difference, which would impact the accuracy of the accelerometer. The improved mechanical design is achieved by double side etching on a specific double-substrate-layer silicon-on-insulator (SOI) wafer to move the center of the proof mass to the support plane. The experimental results demonstrate that the modified design with highly symmetrical structure can suppress the cross-axis sensitivity significantly without compromising the sensitivity and resolution. The cross-axis sensitivity defined by the contrast ratio of the output signal drops to 2.19% /0.1g from 28.28%/0.1g under the premise that the acceleration sensitivity of this single-axis optomechanical accelerometer remains 1162.45V/g and the resolution remains 1.325μg. PMID:27137337

  19. Self-noise models of five commercial strong-motion accelerometers

    Science.gov (United States)

    Ringler, Adam; Evans, John R.; Hutt, Charles R.

    2015-01-01

    Strong‐motion accelerometers provide onscale seismic recordings during moderate‐to‐large ground motions (e.g., up to tens of m/s2 peak). Such instruments have played a fundamental role in improving our understanding of earthquake source physics (Bocketal., 2011), earthquake engineering (Youdet al., 2004), and regional seismology (Zollo et al., 2010). Although strong‐motion accelerometers tend to have higher noise levels than high‐quality broadband velocity seismometers, their higher clip‐levels provide linear recordings at near‐field sites even for the largest of events where a collocated broadband sensor would no longer be able to provide onscale recordings (Clinton and Heaton, 2002).

  20. Movement, resting, and attack behaviors of wild pumas are revealed by tri-axial accelerometer measurements

    OpenAIRE

    Wang, Yiwei; Nickel, Barry; Rutishauser, Matthew; Bryce, Caleb M; Williams, Terrie M; Elkaim, Gabriel; Wilmers, Christopher C.

    2015-01-01

    Background Accelerometers are useful tools for biologists seeking to gain a deeper understanding of the daily behavior of cryptic species. We describe how we used GPS and tri-axial accelerometer (sampling at 64 Hz) collars to monitor behaviors of free-ranging pumas (Puma concolor), which are difficult or impossible to observe in the wild. We attached collars to twelve pumas in the Santa Cruz Mountains, CA from 2010-2012. By implementing Random Forest models, we classified behaviors in wild pu...

  1. An Accelerometer Based Instrumentation of the Golf Club: Measurement and Signal Analysis

    OpenAIRE

    Grober, Robert D.

    2010-01-01

    Two accelerometers are used to measure the motion of the golf club. The accelerometers are mounted in the shaft of the golf club. Each measures the acceleration along the axis of the shaft of the golf club. Interpreting the measurement with the context of the double pendulum model of the golf swing, it is useful to resolve the resulting signals into differential and common mode components. The differential mode is a measure of the rotational kinetic energy of the golf club, and this can be us...

  2. General Relativity Accuracy Test (TEPEE/GReAT): new configuration for the differential accelerometer

    Science.gov (United States)

    Iafolla, V.; Lucchesi, D.; Nozzoli, S.; Santoli, F.; Shapiro, I. I.; Lorenzioni, E. C.; Cosmo, M. L.; Ashenberg, J.; Cheimets, P. N.; Glashow, S.; GReAT

    A key component of experiments to test the Weak Equivalence Principle (WEP), or the universality of free fall, is the differential acceleration detector. The detector must have a very high accuracy in measuring the difference of acceleration, possibly caused by a violation of the Equivalence Principle, acting on a pair of proof masses of different materials. At the same time, the detector must be able to reject common-mode external accelerations and gravity gradients. In this paper, we report the progress in the development of a differential accelerometer that must be able to test the WEP with an accuracy of several parts in 10^15. The detector will be released to free fall inside an evacuated capsule (Einstein elevator) which has been previously dropped from a stratospheric balloon. In order to reach the accuracy goal of the experiment, the accelerometer must attain a sensitivity close to 10^-14 g/Hz^1/2 in a 25 s integration time. The free-fall time is determined by the time that the detector takes to span the co-falling capsule. The detector will be slowly rotated about a horizontal axis to modulate the gravity signal and then released inside the capsule, immediately after the capsule's release from the balloon. First, we describe briefly the overall experiment. Then, we present experimental results obtained with a differential accelerometer prototype, by stressing experimental tests of the sensitivity of the accelerometer read-out system with very-weak signals. Due to the fact that the accelerometer has a resonant frequency as low as 3 Hz and because of the difficulty to attenuate the external noise at such low frequencies, we have carried out acceleration measurements in the laboratory in a region of the seismic noise spectrum, i.e., at frequencies around 10^-1 Hz, where the noise is very low. In addition, we have exploited the ability of the sensor to reject common-mode noise components. Finally, we present a new configuration of the differential

  3. Compact FBG diaphragm accelerometer based on L-shaped rigid cantilever beam

    Institute of Scientific and Technical Information of China (English)

    Yinyan Weng; Xueguang Qiao; Zhongyao Feng; Manli Hu; Jinghua Zhang; YangYang

    2011-01-01

    A compact fiber Bragg grating (FBG) diaphragm accelerometer based on L-shaped rigid cantilever beam is proposed and experimentally demonstrated. The sensing system is based on the integration of a flat diaphragm and an L-shaped rigid cantilever beam. The FBG is pre-tensioned and the two side points are fixed, efficiently avoiding the unwanted chirp effect of grating. Dynamic vibration measurement shows that the proposed FBG diaphragm accelerometer provides a wide frequency response range (0-110 Hz) and an extremely high sensitivity (106.5 pm/g), indemnifying it as a good candidate for embedding structural health monitoring and seismic wave measurement.%A compact fiber Bragg grating (FBG) diaphragm accelerometer based on L-shaped rigid cantilever beam is proposed and experimentally demonstrated.The sensing system is based on the integration of a flat diaphragm and an L-shaped rigid cantilever beam.The FBG is pre-tensioned and the two side points are fixed,efficiently avoiding the unwanted chirp effect of grating.Dynamic vibration measurement shows that the proposed FBG diaphragm accelerometer provides a wide frequency response range (0-110 Hz) and an extremely high sensitivity (106.5 pm/g),indentifying it as a good candidate for embedding structural health monitoring and seismic wave measurement.In the past few decades,accelerometers based on fiber Bragg grating (FBG) have attracted a great deal of interest from researchers and engineers because they play a vital role in vibration measurements.In recent years,FBG accelerometers have been more and more applied in structural health monitoring[1-3) and seismic wave measurement[4-6].This study concerns about the development of geophones composed of FBG accelerometers in seismic exploration.The main frequency of geophones in seismic wave measurement of oil and gas exploration is usually below 100 Hz.An FBG-based accelerometer consisting of a mass resting on a layer of compliant material supported by a rigid base plate

  4. Tracking of Physical Activity with Accelerometers Over a Two-year Time Period

    DEFF Research Database (Denmark)

    Dencker, Magnus; Tanha, Tina; Wollmer, Per;

    2013-01-01

    BACKGROUND: Limited data exists of tracking and changes in accelerometer measured physical activity in children. METHODS: Physical activity was assessed by accelerometers for four days in 167 children (boys n=90, girls n=77), aged 9.8±0.6 years. Follow-up measurement was made 2.0±0.1 yrs later...... (range 1.9-2.1 yrs). General physical activity (GPA) was defined as mean count/minute. Minutes of inactivity, light- moderate- and vigorous physical activity (LMVPA), moderate and vigorous physical activity (MVPA) and vigorous physical activity (VPA) per day were calculated both as absolute values and as...

  5. GOCE gradiometer: estimation of biases and scale factors of all six individual accelerometers by precise orbit determination

    NARCIS (Netherlands)

    Visser, P.N.A.M.

    2008-01-01

    A method has been implemented and tested for estimating bias and scale factor parameters for all six individual accelerometers that will fly on-board of GOCE and together form the so-called gradiometer. The method is based on inclusion of the individual accelerometer observations in precise orbit de

  6. Is there a Sex Difference in Accelerometer Counts During Walking in Older Adults?

    DEFF Research Database (Denmark)

    Van Domelen, Dane R; Caserotti, Paolo; Brychta, Robert J;

    2014-01-01

    Accelerometers have emerged as a useful tool for measuring free-living physical activity in epidemiological studies. Validity of activity estimates depends on the assumption that measurements are equivalent for males and females while performing activities of the same intensity. The primary purpose...

  7. Development and validation of an accelerometer-based method for quantifying gait events.

    Science.gov (United States)

    Boutaayamou, Mohamed; Schwartz, Cédric; Stamatakis, Julien; Denoël, Vincent; Maquet, Didier; Forthomme, Bénédicte; Croisier, Jean-Louis; Macq, Benoît; Verly, Jacques G; Garraux, Gaëtan; Brüls, Olivier

    2015-02-01

    An original signal processing algorithm is presented to automatically extract, on a stride-by-stride basis, four consecutive fundamental events of walking, heel strike (HS), toe strike (TS), heel-off (HO), and toe-off (TO), from wireless accelerometers applied to the right and left foot. First, the signals recorded from heel and toe three-axis accelerometers are segmented providing heel and toe flat phases. Then, the four gait events are defined from these flat phases. The accelerometer-based event identification was validated in seven healthy volunteers and a total of 247 trials against reference data provided by a force plate, a kinematic 3D analysis system, and video camera. HS, TS, HO, and TO were detected with a temporal accuracy ± precision of 1.3 ms ± 7.2 ms, -4.2 ms ± 10.9 ms, -3.7 ms ± 14.5 ms, and -1.8 ms ± 11.8 ms, respectively, with the associated 95% confidence intervals ranging from -6.3 ms to 2.2 ms. It is concluded that the developed accelerometer-based method can accurately and precisely detect HS, TS, HO, and TO, and could thus be used for the ambulatory monitoring of gait features computed from these events when measured concurrently in both feet.

  8. Auto-calibration of capacitive MEMS accelerometers based on pull-in voltage

    NARCIS (Netherlands)

    Rocha, L.A.; Dias, R.A.; Cretu, E.; Mol, L.; Wolffenbuttel, R.F.

    2011-01-01

    This paper describes an electro-mechanical auto-calibration technique for use in capacitive MEMS accelerometers. Auto-calibration is achieved using the combined information derived from an initial measurement of the resonance frequency and the measurement of the pull-in voltages during device operat

  9. Evaluation of Accelerometer Mechanical Filters on Submerged Cylinders Near an Underwater Explosion

    Directory of Open Access Journals (Sweden)

    G. Yiannakopoulos

    1998-01-01

    Full Text Available An accelerometer, mounted to a structure near an explosion to measure elasto-plastic deformation, can be excited at its resonant frequency by impulsive stresses transmitted within the structure. This results in spurious high peak acceleration levels that can be much higher than acceleration levels from the explosion itself. The spurious signals also have higher frequencies than the underlying signal from the explosion and can be removed by a low pass filter. This report assesses the performance of four accelerometer and filter assemblies. The assessment involves measurements of the response of a mild steel cylinder to an underwater explosion, in which each assembly is mounted onto the interior surface of the cylinder. Three assemblies utilise a piezoresistive accelerometer in which isolation is provided mechanically. In the fourth assembly, a piezoelectric accelerometer, with a built-in filter, incorporates both mechanical and electronic filtering. This assembly is found to be more suitable because of its secure mounting arrangement, ease of use, robustness and noise free results.

  10. Testing accelerometer rectification error caused by multidimensional composite inputs with double turntable centrifuge.

    Science.gov (United States)

    Guan, W; Meng, X F; Dong, X M

    2014-12-01

    Rectification error is a critical characteristic of inertial accelerometers. Accelerometers working in operational situations are stimulated by composite inputs, including constant acceleration and vibration, from multiple directions. However, traditional methods for evaluating rectification error only use one-dimensional vibration. In this paper, a double turntable centrifuge (DTC) was utilized to produce the constant acceleration and vibration simultaneously and we tested the rectification error due to the composite accelerations. At first, we deduced the expression of the rectification error with the output of the DTC and a static model of the single-axis pendulous accelerometer under test. Theoretical investigation and analysis were carried out in accordance with the rectification error model. Then a detailed experimental procedure and testing results were described. We measured the rectification error with various constant accelerations at different frequencies and amplitudes of the vibration. The experimental results showed the distinguished characteristics of the rectification error caused by the composite accelerations. The linear relation between the constant acceleration and the rectification error was proved. The experimental procedure and results presented in this context can be referenced for the investigation of the characteristics of accelerometer with multiple inputs.

  11. Activity classification using a single chest mounted tri-axial accelerometer.

    Science.gov (United States)

    Godfrey, A; Bourke, A K; Olaighin, G M; van de Ven, P; Nelson, J

    2011-11-01

    Accelerometer-based activity monitoring sensors have become the most suitable means for objective assessment of mobility trends within patient study groups. The use of minimal, low power, IC (integrated circuit) components within these sensors enable continuous (long-term) monitoring which provides more accurate mobility trends (over days or weeks), reduced cost, longer battery life, reduced size and weight of sensor. Using scripted activities of daily living (ADL) such as sitting, standing, walking, and numerous postural transitions performed under supervised conditions by young and elderly subjects, the ability to discriminate these ADL were investigated using a single tri-axial accelerometer, mounted on the trunk. Data analysis was performed using Matlab® to determine the accelerations performed during eight different ADL. Transitions and transition types were detected using the scalar (dot) product technique and vertical velocity estimates on a single tri-axial accelerometer was compared to a proven discrete wavelet transform method that incorporated accelerometers and gyroscopes. Activities and postural transitions were accurately detected by this simplified low-power kinematic sensor and activity detection algorithm with a sensitivity and specificity of 86-92% for young healthy subjects in a controlled setting and 83-89% for elderly healthy subjects in a home environment. PMID:21636308

  12. A novel class of MEMS accelerometers for very high-G munitions environment

    Science.gov (United States)

    Rastegar, Jahangir; Feng, Dake

    2016-05-01

    The state of art in shock resistant MEMS accelerometer design is to reduce the size of the proof-mass, thereby reducing the generated forces and moments due to shock loading. Physical stops are also provided to limit proof-mass motion to prevent damage to various moving components. The reduction of the proof-mass size reduces the sensor sensitivity. In addition, to increase the sensor dynamic response, proof-mass motion needs to be minimally damped, resulting in a significant sensor settling time after experiencing a high shock loading such as those experienced by gun-fired munitions during firing. The settling time is particularly important for accelerometers that are used in gun-fired munitions and mortars for navigation and guidance. This paper describes the development of a novel class of accelerometers that are provided with the means of locking the sensor proof-mass in its "null" position when subjected to acceleration levels above a prescribed threshold, thereby protecting the moving parts of the accelerometer. In munitions applications, the proof-mass is thereby locked in its null position during the firing and is released during the flight to measure flight acceleration with minimal settling time. Details of the design and operation of the developed sensors and results of their prototyping and testing are presented. The application of the developed technology to other types of inertial sensors and devices is discussed.

  13. The microcontroller processing of signals in precision digital accelerometer with the fiber-optical sensor

    Directory of Open Access Journals (Sweden)

    A. O. Dubikovsky

    2007-10-01

    Full Text Available Features, a principle and operating modes of the three-coordinate fiber-optical sensor are considered. The block diagram and algorithm of processing of a signal precision digital accelerometer with the fiber-optical sensor is offered, expected sizes of key parameters are resulted.

  14. Using accelerometers for physical actions recognition by a neural fuzzy network.

    Science.gov (United States)

    Liu, Shing-Hong; Chang, Yuan-Jen

    2009-11-01

    Triaxial accelerometers were employed to monitor human actions under various conditions. This study aimed to determine an optimum classification scheme and sensor placement positions for recognizing different types of physical action. Three triaxial accelerometers were placed on the chest, waist, and thigh, and their abilities to recognize the three actions of walking, sitting down, and falling were determined. The features of the resultant triaxial signals from each accelerometer were extracted by an autoregression (AR) model. A self-constructing neural fuzzy inference network (SONFIN) was used to recognize the three actions. The performance of the SONFIN was assessed based on statistical parameters, sensitivity, specificity, and total classification accuracy. The results show that the SONFIN provided a stability total classification accuracy of 96.3% and 88.7% for the training and testing data, when the parameters of the 60-order AR model were used as the input feature vector, and the accelerometer was placed anywhere on the abdomen. Seven elderly individuals performing the three basic actions had 80.4% confirmation for the testing data.

  15. Signals and Noises Acting On The Accelerometer Mounted In The Mpo (mercury Planetary Orbiter).

    Science.gov (United States)

    Iafolla, V.; Fiorenza, E.; Lucchesi, D.; Milyukov, V.; Nozzoli, S.

    The RadioScience experiments proposed for the BepiClombo ESA CORNERSTONE are aiming at performing planetary measurements such as: the rotation state of Mer- cury, the global structure of its gravity field and the local gravitational anomalies, but also to test some aspects of the General Relativity, to an unprecedented level of accu- racy. A high sensitivity accelerometer will measure the inertial acceleration acting on the MPO; these data, together with tracking data are used to evaluate the purely gravi- tational trajectory of the MPO, by transforming it to a virtual drag-free satellite system. At the Istituto di Fisica dello Spazio Interplanetario (IFSI) a high sensitive accelerom- eter named ISA (Italian Spring Accelerometer)* and considered for this mission has been studied. The main problems concerning the use of the accelerometer are related to the high dynamics necessary to follow the variation of the acceleration signals, with accuracy equal to 10^-9 g/sqr(Hz), and very high at the MPO orbital period and due to thermal noise introduced at the sidereal period of Mercury. The description of the accelerometer will be presented, with particular attention to the thermal problems and to the analysis regarding the choice of the mounting position on the MPO. *Project funded by the Italian Space Agency (ASI).

  16. Identifying types of physical activity with a single accelerometer: Evaluating laboratory trained algorithms in daily life

    NARCIS (Netherlands)

    Cuba Gyllensten, I.; Bonomi, A.G.

    2011-01-01

    Accurate identification of physical activity types has been achieved in laboratory conditions using single-site accelerometers and classification algorithms. This methodology is then applied to free-living subjects to determine activity behaviour. This study aimed at analysing the reproducibility of

  17. Identification of Capacitive MEMS Accelerometer Structure Parameters for Human Body Dynamics Measurements

    Directory of Open Access Journals (Sweden)

    Vincas Benevicius

    2013-08-01

    Full Text Available Due to their small size, low weight, low cost and low energy consumption, MEMS accelerometers have achieved great commercial success in recent decades. The aim of this research work is to identify a MEMS accelerometer structure for human body dynamics measurements. Photogrammetry was used in order to measure possible maximum accelerations of human body parts and the bandwidth of the digital acceleration signal. As the primary structure the capacitive accelerometer configuration is chosen in such a way that sensing part measures on all three axes as it is 3D accelerometer and sensitivity on each axis is equal. Hill climbing optimization was used to find the structure parameters. Proof-mass displacements were simulated for all the acceleration range that was given by the optimization problem constraints. The final model was constructed in Comsol Multiphysics. Eigenfrequencies were calculated and model’s response was found, when vibration stand displacement data was fed into the model as the base excitation law. Model output comparison with experimental data was conducted for all excitation frequencies used during the experiments.

  18. Validation of the Actical Accelerometer in Multiethnic Preschoolers: The Children's Healthy Living (CHL) Program.

    Science.gov (United States)

    Ettienne, Reynolette; Nigg, Claudio R; Li, Fenfang; Su, Yuhua; McGlone, Katalina; Luick, Bret; Tachibana, Alvin; Carran, Christina; Mercado, Jobel; Novotny, Rachel

    2016-04-01

    This study aimed to determine the validity and reliability of the Actical accelerometer for measuring physical activity (PA) in preschool children of mixed ethnicity, compared with direct observation via a modified System for Observing Fitness Instruction Time (SOFIT) protocol and proxy parental reports (PA Logs). Fifty children in Hawai'i wore wrist-mounted accelerometers for two 7-day periods with a washout period between each week. Thirty children were concurrently observed using SOFIT. Parents completed PA Logs for three days. Reliability and validity were measured by intra-class correlation coefficient and proportions of agreement concurrently. There was slight agreement (proportion of agreement: 82%; weighted Kappa=.17, P SOFIT as well as between the accelerometer and the PA Logs (proportions of agreement: 40%; weighted Kappa=0.15, P <.001). PA logs underestimated the PA levels of the children, while the Actical was found to be valid and reliable for estimating PA levels of multiethnic, mixed ethnicity preschoolers. These findings suggest that accelerometers can be objective, valid, and accurate physical activity assessment tools compared to conventional PA logs and subjective reports of activity for preschool children of mixed ethnicity. PMID:27099804

  19. Physical activity, cognitive performance, and academic achievement: an observational study in Dutch adolescents using accelerometers

    NARCIS (Netherlands)

    Van Dijk, Martin; De Groot, Renate; Savelberg, Hans; Van Acker, Frederik; Kirschner, Paul A.

    2013-01-01

    Van Dijk, M. L., De Groot, R. H. M., Savelberg, H. C. M., Van Acker, F. H. M., & Kirschner, P. A. (2013, 7 November). Physical activity, cognitive performance, and academic achievement: an observational study in Dutch adolescents using accelerometers. Paper presentation at ICO National Fall School 2

  20. Physical activity, cognitive performance, and academic achievement: an observational study in Dutch adolescents using accelerometers

    OpenAIRE

    Van Dijk, Martin; De Groot, Renate; Savelberg, Hans; Van Acker, Frederik; Kirschner, Paul A.

    2013-01-01

    Van Dijk, M. L., De Groot, R. H. M., Savelberg, H. C. M., Van Acker, F. H. M., & Kirschner, P. A. (2013, 7 November). Physical activity, cognitive performance, and academic achievement: an observational study in Dutch adolescents using accelerometers. Paper presentation at ICO National Fall School 2013, Maastricht, The Netherlands.

  1. Experiment on interface separation detection of concrete-filled steel tubular arch bridge using accelerometer array

    Science.gov (United States)

    Pan, Shengshan; Zhao, Xuefeng; Zhao, Hailiang; Mao, Jian

    2015-04-01

    Based on the vibration testing principle, and taking the local vibration of steel tube at the interface separation area as the study object, a real-time monitoring and the damage detection method of the interface separation of concrete-filled steel tube by accelerometer array through quantitative transient self-excitation is proposed. The accelerometers are arranged on the steel tube area with or without void respectively, and the signals of accelerometers are collected at the same time and compared under different transient excitation points. The results show that compared with the signal of compact area, the peak value of accelerometer signal at void area increases and attenuation speed slows down obviously, and the spectrum peaks of the void area are much more and disordered and the amplitude increases obviously. whether the input point of transient excitation is on void area or not is irrelevant with qualitative identification results. So the qualitative identification of the interface separation of concrete-filled steel tube based on the signal of acceleration transducer is feasible and valid.

  2. Modelling fat mass as a function of weekly physical activity profiles measured by Actigraph accelerometers

    International Nuclear Information System (INIS)

    We show results on the Avon longitudinal study of parents and children (ALSPAC) using a new approach for modelling the relationship between health outcomes and physical activity assessed by accelerometers. The key feature of the model is that it uses the histogram of physical activity counts as a predictor function, rather than scalar summary measures such as average daily moderate to vigorous physical activity (MVPA). Three models are fitted: (1a) A regression of fat mass at age 12 (N = 4164) onto the histogram of accelerometer counts at age 12; (1b) A regression of fat mass at age 14 (N = 2403) onto the histogram of accelerometer counts at age 12 and (1c) a regression of fat mass at age 14 (N = 2413) onto the accelerometer counts at age 14. All three models significantly improve on models including MVPA instead of the histogram and improve the goodness of fit of models (2a), (2b) and (2c) from R2 = 0.267, 0.248 and 0.230 to R2 = 0.292, 0.263 and 0.258 for models (1a), (1b) and (1c) respectively. The proportion of time spent in sedentary and very light activity (corresponding to slow walking and similar activities) has a positive contribution towards fat mass and time spent in moderate to vigorous activity has a negative contribution towards fat mass. (paper)

  3. Comparison of Yamax pedometer and GT3X accelerometer steps in a free-living sample

    Science.gov (United States)

    Our objective was to compare steps detected by the Yamax pedometer (PEDO) versus the GT3X accelerometer (ACCEL) in free-living adults. Daily PEDO and ACCEL steps were collected from a sample of 23 overweight and obese participants (18 females; mean +/- sd: age = 52.6 +/- 8.4 yr.; body mass index = 3...

  4. Detection of generalized tonic-clonic seizures by a wireless wrist accelerometer

    DEFF Research Database (Denmark)

    Beniczky, S.; Hjalgrim, Helle; Polster, T.;

    2013-01-01

    Our objective was to assess the clinical reliability of a wrist-worn, wireless accelerometer sensor for detecting generalized tonic-clonic seizures (GTCS). Seventy-three consecutive patients (age 6-68 years; median 37 years) at risk of having GTCS and who were admitted to the long-term video-elec...

  5. Measurement of six degree-of-freedom ground motion by using eight accelerometers

    Institute of Scientific and Technical Information of China (English)

    Yang Zhenyu; Shen Yi; Liu Zhiyan

    2005-01-01

    A new integrated measuring system with eight force-balance accelerometers is proposed to obtain a direct measurement of six degree-of freedom (DOF) ground motions, including three rotational and three actual translational acceleration components without gyroscopes. In the proposed measuring system, the relationship between the output from eight force-balance accelerometer and the six DOF motion of the measuring system under an earthquake are described by differential equations. These equations are derived from the positions and directions of the eight force-balance accelerometers in the measuring system. The third-order Runge-Kutta algorithm is used to guarantee the accuracy of the numerical calculation. All the algorithms used to compute the six DOF components of the ground motion are implemented in a real-time in Digital Signal Processor (DSP). The distortion of the measured results caused by position and direction errors of the accelerometers in the measuring system are reduced by multiplying a compensation coefficient C to the output and subtracting static zero drift from the measured results, respectively.

  6. Wearable Goniometer and Accelerometer Sensory Fusion for Knee Joint Angle Measurement in Daily Life

    Directory of Open Access Journals (Sweden)

    Alessandro Tognetti

    2015-11-01

    Full Text Available Human motion analysis is crucial for a wide range of applications and disciplines. The development and validation of low cost and unobtrusive sensing systems for ambulatory motion detection is still an open issue. Inertial measurement systems and e-textile sensors are emerging as potential technologies for daily life situations. We developed and conducted a preliminary evaluation of an innovative sensing concept that combines e-textiles and tri-axial accelerometers for ambulatory human motion analysis. Our sensory fusion method is based on a Kalman filter technique and combines the outputs of textile electrogoniometers and accelerometers without making any assumptions regarding the initial accelerometer position and orientation. We used our technique to measure the flexion-extension angle of the knee in different motion tasks (monopodalic flexions and walking at different velocities. The estimation technique was benchmarked against a commercial measurement system based on inertial measurement units and performed reliably for all of the various tasks (mean and standard deviation of the root mean square error of 1:96 and 0:96, respectively. In addition, the method showed a notable improvement in angular estimation compared to the estimation derived by the textile goniometer and accelerometer considered separately. In future work, we will extend this method to more complex and multi-degree of freedom joints.

  7. Using an inertial navigation algorithm and accelerometer to monitor chest compression depth during cardiopulmonary resuscitation.

    Science.gov (United States)

    Boussen, Salah; Ibouanga-Kipoutou, Harold; Fournier, Nathalie; Raboutet, Yves Godio; Llari, Maxime; Bruder, Nicolas; Arnoux, Pierre Jean; Behr, Michel

    2016-09-01

    We present an original method using a low cost accelerometer and a Kalman-filter based algorithm to monitor cardiopulmonary resuscitation chest compressions (CC) depth. A three-axis accelerometer connected to a computer was used during CC. A Kalman filter was used to retrieve speed and position from acceleration data. We first tested the algorithm for its accuracy and stability on surrogate data. The device was implemented for CC performed on a manikin. Different accelerometer locations were tested. We used a classical inertial navigation algorithm to reconstruct CPR depth and frequency. The device was found accurate enough to monitor CPR depth and its stability was checked for half an hour without any drift. Average error on displacement was ±0.5mm. We showed that depth measurement was dependent on the device location on the patient or the rescuer. The accuracy and stability of this small low-cost accelerometer coupled to a Kalman-filter based algorithm to reconstruct CC depth and frequency, was found well adapted and could be easily implemented. PMID:27246666

  8. Measuring Height of an Object using Accelerometer and Camera in iOS and Android Devices

    OpenAIRE

    Anmole Dewan; Abhijeet Sharma; Tanupriya Choudhary; Vasudha Vashisht

    2014-01-01

    The height of object can be determined by using inch tapes, angles of elevation and basic trigonometry. Everything listed can be replaced by using standard smart phones having accelerometer, GPS receiver, network connectivity and camera. The research deals with calculation of height of an object by converting data received from the sensors.

  9. A novel class of MEMS accelerometers for guidance and control of gun-fired munitions

    Science.gov (United States)

    Rastegar, Jahangir; Feng, Dake; Pereira, Carlos M.

    2015-05-01

    The state of art in shock resistant MEMS accelerometer design is to reduce the size of the proof-mass, thereby reducing the generated forces and moments due to shock loading. Physical stops are also provided to limit proof-mass motion to prevent damage to various moving components. The reduction of the proof-mass size reduces the sensor sensitivity. In addition, to increase the sensor dynamic response, proof-mass motion needs to be minimally damped, resulting in a significant sensor settling time after experiencing a high shock loading such as those experienced by gun-fired munitions during firing. The settling time is particularly important for accelerometers that are used in gun-fired munitions and mortars for navigation and guidance. This paper describes the development of a novel class of accelerometers that are provided with the means of locking the sensor proof-mass in its "null" position when subjected to acceleration levels above prescribed thresholds, thereby protecting the moving parts of the accelerometer. In munitions applications, the proof-mass is thereby locked in its null position during the firing and released during the flight to begin to measure flight acceleration with minimal settling time. Details of the design and operation of the developed sensors and results of their prototyping and testing are presented. The application of the developed technology to other types of inertial sensors and devices is discussed.

  10. A wireless accelerometer node for reliable and valid measurement of lumbar accelerations during treadmill running.

    Science.gov (United States)

    Lindsay, Timothy R; Yaggie, James A; McGregor, Stephen J

    2016-01-01

    This study investigated the reliability of a wireless accelerometer and its agreement with optical motion capture for the measurement of root mean square (RMS) acceleration during running. RMS acceleration provides a whole-body metric of movement mechanics and economy. Fifteen healthy college-age participants performed treadmill running for two 60-s trials at 2.22, 2.78, and 3.33 m/s and one trial of 150 s (five 30-s epochs) at 2.78 m/s. We assessed between-trial and within-trial reliability, and agreement in each axis between a trunk-mounted wireless accelerometer and a reflective marker on the accelerometer measured by optical motion capture. Intraclass correlations assessing between-trial repeatability were 0.89-0.97, depending on the axis, and intraclass correlations assessing within-trial repeatability were 0.99-1.00. Bland-Altman analyses assessing agreement indicated mean difference values between -0.03 and 0.03 g, depending on the axis. Anterio-posterior acceleration had the greatest limits of agreement (LOA) (±0.12 g) and vertical acceleration had the smallest LOA (±0.03 g). For measuring RMS acceleration of the trunk, this wireless accelerometer node provides repeatable and valid measurement compared with the standard laboratory method of optical motion capture.

  11. Optimal Methods of RTK-GPS/Accelerometer Integration to Monitor the Displacement of Structures

    Directory of Open Access Journals (Sweden)

    Sungnam Hong

    2012-01-01

    Full Text Available The accurate measurement of diverse displacements of structures is an important index for the evaluation of a structure’s safety. In this study, a comparative analysis was conducted to determine the integrated RTK-GPS/accelerometer method that can provide the most precise structure displacement measurements. For this purpose, three methods of calculating the dynamic displacements from the acceleration data were comparatively analyzed. In addition, two methods of determining dynamic, static, and quasi-static displacements by integrating the displacements measured from the RTK-GPS system and the accelerometer were also comparatively analyzed. To ensure precise comparison results, a cantilever beam was manufactured onto which diverse types of displacements were generated to evaluate the measurement accuracy by method. Linear variable differential transformer (LVDT measurements were used as references for the evaluation to ensure accuracy. The study results showed that the most suitable method of measuring the dynamic displacement with the accelerometer was to calculate the displacement by filtering and double-integrating the acceleration data using the FIR band-pass filter. The integration method that uses frequency-based displacement extraction was most appropriate for the integrated RTK-GPS/accelerometer method of comprehensively measuring the dynamic, static, and quasi-static displacements.

  12. Accelerometer and rate gyroscope measurement of kinematics: an inexpensive alternative to optical motion analysis systems

    NARCIS (Netherlands)

    Mayagoitia, Ruth E.; Nene, Anand V.; Veltink, Peter H.

    2002-01-01

    A general-purpose system to obtain the kinematics of gait in the sagittal plane based on body-mounted sensors was developed. It consisted of four uniaxial seismic accelerometers and one rate gyroscope per body segment. Tests were done with 10 young healthy volunteers, walking at five different speed

  13. Identification of children's activity type with accelerometer-based neural networks

    NARCIS (Netherlands)

    Vries, S.I. de; Engels, M.; Garre, F.G.

    2011-01-01

    Purpose: The study's purpose was to identify children's physical activity type using artificial neural network (ANN) models based on uniaxial or triaxial accelerometer data from the hip or the ankle. Methods: Fifty-eight children (31 boys and 27 girls, age range = 9-12 yr) performed the following ac

  14. Wearable Goniometer and Accelerometer Sensory Fusion for Knee Joint Angle Measurement in Daily Life.

    Science.gov (United States)

    Tognetti, Alessandro; Lorussi, Federico; Carbonaro, Nicola; de Rossi, Danilo

    2015-11-11

    Human motion analysis is crucial for a wide range of applications and disciplines. The development and validation of low cost and unobtrusive sensing systems for ambulatory motion detection is still an open issue. Inertial measurement systems and e-textile sensors are emerging as potential technologies for daily life situations. We developed and conducted a preliminary evaluation of an innovative sensing concept that combines e-textiles and tri-axial accelerometers for ambulatory human motion analysis. Our sensory fusion method is based on a Kalman filter technique and combines the outputs of textile electrogoniometers and accelerometers without making any assumptions regarding the initial accelerometer position and orientation. We used our technique to measure the flexion-extension angle of the knee in different motion tasks (monopodalic flexions and walking at different velocities). The estimation technique was benchmarked against a commercial measurement system based on inertial measurement units and performed reliably for all of the various tasks (mean and standard deviation of the root mean square error of 1:96 and 0:96, respectively). In addition, the method showed a notable improvement in angular estimation compared to the estimation derived by the textile goniometer and accelerometer considered separately. In future work, we will extend this method to more complex and multi-degree of freedom joints.

  15. Using an accelerometer for analyzing a reach-to-grasp movement after stroke

    Directory of Open Access Journals (Sweden)

    Stella Maris Michaelsen

    2013-12-01

    Full Text Available The purpose of this study was using an accelerometer to access the kinematics of reach-to-grasp movements in subjects with hemiparesis. Eight subjects (59.4 ± 6.9 years old with chronic hemiparesis (50.9 ± 25.8 months post-stroke participated in this study. Kinematic assessment was performed using a triaxial accelerometer (EMG Systems, Brazil attached to the subjects' forearm. Ten reach-to-grasp movements of grabbing a 500ml-size bottle were performed by the subjects with the paretic and the non-paretic upper limbs (ULs. The following space-temporal variables were calculated and used to compare the paretic and non-paretic ULs: movement time (MT, time to reach the peak velocity, absolute and relative (TPV and TPV%MT, relative deceleration duration (DEC%MT, time to peak acceleration (TPA and peak hand acceleration (PA. Movements were slower in the paretic UL with increased MT, TPA and DEC. The accelerometer allowed to identify of changes in reaching-to-grasp movements of subjects with hemiparesis. When complex systems are not available, accelerometers can be an alternative to measure UL movements.

  16. Validity of an Accelerometer-Based Activity Monitor System for Measuring Physical Activity in Frail Elderly

    NARCIS (Netherlands)

    Hollewand, Anne M; Spijkerman, Anouk G; Bilo, Henk J; Kleefstra, Nanne; Kamsma, Yvo; van Hateren, Kornelis J

    2016-01-01

    This study aimed to investigate the validity of the accelerometer-based DynaPort system to detect physical activity in frail elderly subjects. Eighteen home-dwelling subjects (Groningen Frailty Indicator (GFI) score ≥4, ≥75 years) were included. Activities in their home environment were simultaneous

  17. Fiber Optic 3-D Space Piezoelectric Accelerometer and its Antinoise Technology

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The mechanical structure of piezoelectric accelerometer is designed, and the operation equations on X-, Y-, and Z-axes are deduced. The test results of 3-D frequency response are given. Noise disturbances are effectively eliminated by using fiber optic transmission and synchronous detection.

  18. Reliability of the Actigraph GT3X+ Accelerometer in Adults under Free-Living Conditions.

    Directory of Open Access Journals (Sweden)

    Eivind Aadland

    Full Text Available Reliability of the Actigraph GT3X+ accelerometer has not been determined under normal wear time criteria in a large sample of subjects and accelerometer units. The aim of this study was to assess contralateral hip difference and inter-instrument reliability of the Actigraph GT3X+ monitor in adults under long-term free-living conditions.Eighty-seven adult subjects (28 men; mean (standard deviation age 31.3 (12.2 years; body mass index 23.7 (3.1 kg/m2 concurrently wore two GT3X+ accelerometers (174 units in total attached to contralateral hips for 21 days. Reliability was assessed using Bland-Altman plots, mixed model regression analyses and absolute measures of agreement for different lengths of data accumulation (single-day-, 7-day- and 21-day periods.There were no significant differences between contralateral hips (effect size ≤0.042; p ≥.213. Inter-instrument reliability increased with increased length of data-accumulation. For a 7-day measurement period (n = 232 weeks, limits of agreement were ±68 cpm (vertical axis and ±81.3 cpm (vector magnitude for overall physical activity (PA level, ±51 min for sedentary time, ±18.2 min for light PA, ±6.3 min for moderate PA, ±3.5 min for vigorous PA, and ±6.7 min for moderate-to-vigorous PA.The Actigraph GT3X+ accelerometer is a reliable tool for measuring PA in adults under free-living conditions using normal data-reduction criteria. Contralateral hip differences are very small. We suggest accelerometers be attached to the right hip and data to be accumulated over several days of measurement.

  19. High Shock, High Frequency Characteristics of a Mechanical Isolator for a Piezoresistive Accelerometer, the ENDEVCO 7270AM6*

    Energy Technology Data Exchange (ETDEWEB)

    BATEMAN,VESTA I.; BROWN,FREDERICK A.; NUSSER,MICHAEL A.

    2000-07-01

    A mechanical isolator has been developed for a piezoresistive accelerometer. The purpose of the isolator is to mitigate high frequency shocks before they reach the accelerometer because the high frequency shocks may cause the accelerometer to resonate. Since the accelerometer is undamped, it often breaks when it resonates. The mechanical isolator was developed in response to impact test requirements for a variety of structures at Sandia National Laboratories (SNL). An Extended Technical Assistance Program (ETAP) with the accelerometer manufacturer has resulted in a commercial mechanically isolated accelerometer that is available to the general public, the ENDEVCO 7270AM6*, for three shock acceleration ranges of 6,000 g, 20,000 g, and 60,000 g. The in-axis response shown in this report has acceptable frequency domain performance from DC to 10 kHz and 10(XO)over a temperature range of {minus}65 F to +185 F. Comparisons with other isolated accelerometers show that the ENDEVCO 7270AM6 has ten times the bandwidth of any other commercial isolator. ENDEVCO 7270AM6 cross-axis response is shown in this report.

  20. A random forest classifier for the prediction of energy expenditure and type of physical activity from wrist and hip accelerometers

    International Nuclear Information System (INIS)

    Wrist accelerometers are being used in population level surveillance of physical activity (PA) but more research is needed to evaluate their validity for correctly classifying types of PA behavior and predicting energy expenditure (EE). In this study we compare accelerometers worn on the wrist and hip, and the added value of heart rate (HR) data, for predicting PA type and EE using machine learning. Forty adults performed locomotion and household activities in a lab setting while wearing three ActiGraph GT3X+ accelerometers (left hip, right hip, non-dominant wrist) and a HR monitor (Polar RS400). Participants also wore a portable indirect calorimeter (COSMED K4b2), from which EE and metabolic equivalents (METs) were computed for each minute. We developed two predictive models: a random forest classifier to predict activity type and a random forest of regression trees to estimate METs. Predictions were evaluated using leave-one-user-out cross-validation. The hip accelerometer obtained an average accuracy of 92.3% in predicting four activity types (household, stairs, walking, running), while the wrist accelerometer obtained an average accuracy of 87.5%. Across all 8 activities combined (laundry, window washing, dusting, dishes, sweeping, stairs, walking, running), the hip and wrist accelerometers obtained average accuracies of 70.2% and 80.2% respectively. Predicting METs using the hip or wrist devices alone obtained root mean square errors (rMSE) of 1.09 and 1.00 METs per 6 min bout, respectively. Including HR data improved MET estimation, but did not significantly improve activity type classification. These results demonstrate the validity of random forest classification and regression forests for PA type and MET prediction using accelerometers. The wrist accelerometer proved more useful in predicting activities with significant arm movement, while the hip accelerometer was superior for predicting locomotion and estimating EE. (paper)

  1. Three-component hybrid-integrated optical accelerometer based on LiNbO3 photoelastic waveguide

    Institute of Scientific and Technical Information of China (English)

    Donglin Tang; Zheng Liang; Xiaodong Zhang; Shan He; Feng Guo

    2009-01-01

    A novel three-component hybrid-integrated optical accelerometer based on LiNbO3 photoelastic waveguide is presented. The photoelasitcity of LiNbO3 due to three-dimensional stress states is obtained analytically. We analyze the level of sensitivity to cross-axis accelerations which is a very important parameter for three-component accelerometer. Theoretically, the designed three-component hybrid-integrated optical accelerometer has a transverse sensitivity ratio (TSR) of zero. The sensor has a high natural frequency of 3.5 kHz and a linear broad working frequency.

  2. Quality control methods in accelerometer data processing: defining minimum wear time.

    Directory of Open Access Journals (Sweden)

    Carly Rich

    Full Text Available BACKGROUND: When using accelerometers to measure physical activity, researchers need to determine whether subjects have worn their device for a sufficient period to be included in analyses. We propose a minimum wear criterion using population-based accelerometer data, and explore the influence of gender and the purposeful inclusion of children with weekend data on reliability. METHODS: Accelerometer data obtained during the age seven sweep of the UK Millennium Cohort Study were analysed. Children were asked to wear an ActiGraph GT1M accelerometer for seven days. Reliability coefficients(r of mean daily counts/minute were calculated using the Spearman-Brown formula based on the intraclass correlation coefficient. An r of 1.0 indicates that all the variation is between- rather than within-children and that measurement is 100% reliable. An r of 0.8 is often regarded as acceptable reliability. Analyses were repeated on data from children who met different minimum daily wear times (one to 10 hours and wear days (one to seven days. Analyses were conducted for all children, separately for boys and girls, and separately for children with and without weekend data. RESULTS: At least one hour of wear time data was obtained from 7,704 singletons. Reliability increased as the minimum number of days and the daily wear time increased. A high reliability (r = 0.86 and sample size (n = 6,528 was achieved when children with ≥ two days lasting ≥10 hours/day were included in analyses. Reliability coefficients were similar for both genders. Purposeful sampling of children with weekend data resulted in comparable reliabilities to those calculated independent of weekend wear. CONCLUSION: Quality control procedures should be undertaken before analysing accelerometer data in large-scale studies. Using data from children with ≥ two days lasting ≥10 hours/day should provide reliable estimates of physical activity. It's unnecessary to include only children

  3. Electrostatic Accelerometer for the Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Perrot, Eddy; Boulanger, Damien; Christophe, Bruno; Foulon, Bernard; Liorzou, Françoise; Lebat, Vincent

    2014-05-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, that will produce an accurate model of the Earth's gravity field variation providing global climatic data during five year at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link, and optionally a laser link, measuring the inter-satellites distance variation. Non-uniformities in the distribution of the Earth's mass cause the distance between the two satellites to vary. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics - SUM - and the Front-End Electronic Unit - FEEU) and the Interface Control Unit. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained in a center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The Preliminary Design Review was achieved successfully on November 2013. The FEEU Engineering Model is under test. Preliminary results on electronic unit will be compared with the expected performance. The integration of the SUM Engineering Model and the first ground levitation of the proof-mass will be presented. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with

  4. Identification of electrically stimulated quadriceps - lower leg dynamics - the use of accelerometers for estimating knee joint acceleration and quadriceps torque

    NARCIS (Netherlands)

    Veltink, Peter H.; Tijsmans, Roel; Franken, Henry M.; Boom, Herman B.K.

    1992-01-01

    Knee joiiit acceleration aid quadriceps torque call be estbated from the signals of two tangentially yliiced accelerometers. This euables the ideutificatiou of qundriceps dynamics, loaded with a freely swiugiug lower leg, during electrical stimulation.

  5. Construct validity of RT3 accelerometer: A comparison of level-ground and treadmill walking at self-selected speeds

    Directory of Open Access Journals (Sweden)

    Paul Hendrick, MPhty

    2010-04-01

    Full Text Available This study examined differences in accelerometer output when subjects walked on level ground and on a treadmill. We asked 25 nondisabled participants to wear an RT3 triaxial accelerometer (StayHealthy, Inc; Monrovia, California and walk at their "normal" and "brisk" walking speeds for 10 minutes. These activities were repeated on a treadmill using the individual speeds from level-ground walking on two occasions 1 week apart. Paired t-tests found a difference in RT3 accelerometer vector magnitude (VM counts/min between the two walking speeds on both surfaces on days 1 and 2 (p 0.05, we found wide limits of agreement between level ground and treadmill walking at both speeds. Measurement and discrimination of walking intensity employing RT3 accelerometer VM counts/min on the treadmill demonstrated reasonable validity and stability over two time points compared with level-ground walking.

  6. Simulation of a low frequency Z-axis SU-8 accelerometer in coventorware and MEMS+

    KAUST Repository

    Carreno, Armando Arpys Arevalo

    2013-04-01

    This paper presents the simulation of a z-axis SU-8 capacitive accelerometer. The study consists of a modal analysis of the modeled accelerometer, a study relating capacitance to acceleration, capacitance to deflection, an effective spring constant calculation, and a comparison of results achieved using CoventorWare® ANALYZER™ and MEMS+®. A fabricated energy harvester design from [1] was used for modeling and simulation in this study, with a four spring attachment of a 650μm×650μm; ×110μm proof mass of 4.542×10-8 kg. At rest, the spacing between electrodes is 4μm along the z-axis, and at 1.5g acceleration, there is 1.9μm spacing between electrodes, at which point pull in occurs for a 1V voltage. © 2013 IEEE.

  7. Fiber optic gyro/silicon accelerometer inertial measurement unit, test results

    Science.gov (United States)

    Matthews, A.; Weintraub, M.

    Under an SDI contract a small, lightweight Inertial Measurement Unit (IMU) was developed that uses two new technologies namely, Fiber Optic Gyros and miniature micromachined single-crystal Silicon Accelerometers. This paper describes the theory of operation of the two new inertial instruments which lead to an IMU of high sensitivity, wide bandwidth, low noise, low weight and rapid reaction; ideal for many Strategic Defense Initiatives (SDI), military and commercial applications. A flyable brassboard model of the IMU was built with three miniature Fiber Optic Gyros (FOG) and three silicon accelerometers. The brassboard model was tested under static and dynamic conditions in a laboratory and the test data compared favorably to the performance objectives. This paper concludes by forecasting the next phase, continued miniaturization, and adaptation to missiles and aircraft compass/Altitude and Heading Reference Systems (AHRS) for many applications.

  8. Comprehensive Warpage Analysis of Stacked Die MEMS Package in Accelerometer Application

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Packaging of MEMS ( micro-electro-mechanical system ) devices poses more challenges than conventional IC packaging, since the performance of the MEMS devices is highly dependent on packaging processes. A Land Grid Array (LGA) package is introduced for MEMS technology based linear multi-axis accelerometers. Finite element modeling is conducted to simulate the warpage behavior of the LGA packages. A method to correlate the package warpage to matrix block warpage has been developed. Warpage for both package and sensor substrate are obtained. Warpage predicted by simulation correlates very well with experimental measurements. Based on this validated method, detailed design analysis with different package geometrical variations are carried out to optimize the package design. With the optimized package structure,the packaging effect on accelerometer signal performance is well controlled.

  9. An Accelerometer Based Instrumentation of the Golf Club: Measurement and Signal Analysis

    CERN Document Server

    Grober, Robert D

    2010-01-01

    Two accelerometers are used to measure the motion of the golf club. The accelerometers are mounted in the shaft of the golf club. Each measures the acceleration along the axis of the shaft of the golf club. Interpreting the measurement with the context of the double pendulum model of the golf swing, it is useful to resolve the resulting signals into differential and common mode components. The differential mode is a measure of the rotational kinetic energy of the golf club, and this can be used to understand the tempo, rhythm, and timing of the golf swing. The common mode measurement is related to the motion of the hands. It is shown that both components can be used to recover the motion of the swing within the context of the double pendulum model of the golf swing.

  10. Off-the-shelf mobile handset environments for deploying accelerometer based gait and activity analysis algorithms.

    Science.gov (United States)

    Hynes, Martin; Wang, Han; Kilmartin, Liam

    2009-01-01

    Over the last decade, there has been substantial research interest in the application of accelerometry data for many forms of automated gait and activity analysis algorithms. This paper introduces a summary of new "of-the-shelf" mobile phone handset platforms containing embedded accelerometers which support the development of custom software to implement real time analysis of the accelerometer data. An overview of the main software programming environments which support the development of such software, including Java ME based JSR 256 API, C++ based Motion Sensor API and the Python based "aXYZ" module, is provided. Finally, a sample application is introduced and its performance evaluated in order to illustrate how a standard mobile phone can be used to detect gait activity using such a non-intrusive and easily accepted sensing platform. PMID:19964383

  11. Three 3-axis accelerometers fixed inside the tyre for studying contact patch deformations in wet conditions

    Science.gov (United States)

    Niskanen, Arto J.; Tuononen, Ari J.

    2014-05-01

    The tyre-road contact area was studied visually by means of a high-speed camera and three accelerometers fixed to the inner liner of the tyre carcass. Both methods show a distorted contact area in wet conditions, but interesting differences appeared. First, the contact area in full aquaplaning seems strongly distorted on a glass plate when subjected to visual inspection, while the accelerometers indicate a more even hydrodynamic aquaplaning contact length (CL) across the tyre width. Secondly, the acceleration sensors predict the clear shortening of the CL of the tyre before the critical aquaplaning speed. It can be concluded that the visual contact area and shape are heavily dependent on the transparency of the liquid and smoothness of the glass. Meanwhile, the tyre sensors can provide a CL estimate on any road surface imaginable.

  12. Design and validation of a high-voltage levitation circuit for electrostatic accelerometers

    Energy Technology Data Exchange (ETDEWEB)

    Li, G.; Wu, S. C.; Zhou, Z. B.; Bai, Y. Z.; Hu, M.; Luo, J. [MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

    2013-12-15

    A simple high-voltage circuit with a voltage range of 0 to 900 V and an open-loop bandwidth of 11 kHz is realized by using an operational amplifier and a MOSFET combination. The circuit is used for the levitation of a test mass of 71 g, suspended below the top-electrodes with a gap distance of 57 μm, so that the performance of an electrostatic accelerometer can be tested on the ground. The translation noise of the accelerometer, limited by seismic noise, is about 4 × 10{sup −8} m/s{sup 2}/Hz{sup 1/2} at 0.1 Hz, while the high-voltage coupling noise is one-order of magnitude lower.

  13. Experimental Robot Position Sensor Fault Tolerance Using Accelerometers and Joint Torque Sensors

    Science.gov (United States)

    Aldridge, Hal A.; Juang, Jer-Nan

    1997-01-01

    Robot systems in critical applications, such as those in space and nuclear environments, must be able to operate during component failure to complete important tasks. One failure mode that has received little attention is the failure of joint position sensors. Current fault tolerant designs require the addition of directly redundant position sensors which can affect joint design. The proposed method uses joint torque sensors found in most existing advanced robot designs along with easily locatable, lightweight accelerometers to provide a joint position sensor fault recovery mode. This mode uses the torque sensors along with a virtual passive control law for stability and accelerometers for joint position information. Two methods for conversion from Cartesian acceleration to joint position based on robot kinematics, not integration, are presented. The fault tolerant control method was tested on several joints of a laboratory robot. The controllers performed well with noisy, biased data and a model with uncertain parameters.

  14. The association between park visitation and physical activity measured with accelerometer, GPS, and travel diary.

    Science.gov (United States)

    Stewart, Orion T; Moudon, Anne Vernez; Fesinmeyer, Megan D; Zhou, Chuan; Saelens, Brian E

    2016-03-01

    Public parks are promoted as places that support physical activity (PA), but evidence of how park visitation contributes to overall PA is limited. This study observed adults living in the Seattle metropolitan area (n=671) for one week using accelerometer, GPS, and travel diary. Park visits, measured both objectively (GPS) and subjectively (travel diary), were temporally linked to accelerometer-measured PA. Park visits occurred at 1.4 per person-week. Participants who visited parks at least once (n=308) had an adjusted average of 14.3 (95% CI: 8.9, 19.6)min more daily PA than participants who did not visit a park. Even when park-related activity was excluded, park visitors still obtained more minutes of daily PA than non-visitors. Park visitation contributes to a more active lifestyle, but is not solely responsible for it. Parks may best serve to complement broader public health efforts to encourage PA. PMID:26798965

  15. 116 dB dynamic range CMOS readout circuit for MEMS capacitive accelerometer

    International Nuclear Information System (INIS)

    A high stability in-circuit reprogrammable technique control system for a capacitive MEMS accelerometer is presented. Modulation and demodulation are used to separate the signal from the low frequency noise. A low-noise low-offset charge integrator is employed in this circuit to implement a capacitance-to-voltage converter and minimize the noise and offset. The application-specific integrated circuit (ASIC) is fabricated in a 0.5 μm one-ploy three-metal CMOS process. The measured results of the proposed circuit show that the noise floor of the ASIC is −116 dBV, the sensitivity of the accelerometer is 66 mV/g with a nonlinearity of 0.5%. The chip occupies 3.5 × 2.5 mm2 and the current is 3.5 mA. (semiconductor integrated circuits)

  16. Gait Characteristic Analysis and Identification Based on the iPhone’s Accelerometer and Gyrometer

    Directory of Open Access Journals (Sweden)

    Bing Sun

    2014-09-01

    Full Text Available Gait identification is a valuable approach to identify humans at a distance. In thispaper, gait characteristics are analyzed based on an iPhone’s accelerometer and gyrometer,and a new approach is proposed for gait identification. Specifically, gait datasets are collectedby the triaxial accelerometer and gyrometer embedded in an iPhone. Then, the datasets areprocessed to extract gait characteristic parameters which include gait frequency, symmetrycoefficient, dynamic range and similarity coefficient of characteristic curves. Finally, aweighted voting scheme dependent upon the gait characteristic parameters is proposed forgait identification. Four experiments are implemented to validate the proposed scheme. Theattitude and acceleration solutions are verified by simulation. Then the gait characteristicsare analyzed by comparing two sets of actual data, and the performance of the weightedvoting identification scheme is verified by 40 datasets of 10 subjects.

  17. Gait characteristic analysis and identification based on the iPhone's accelerometer and gyrometer.

    Science.gov (United States)

    Sun, Bing; Wang, Yang; Banda, Jacob

    2014-09-12

    Gait identification is a valuable approach to identify humans at a distance. In this paper, gait characteristics are analyzed based on an iPhone's accelerometer and gyrometer,and a new approach is proposed for gait identification. Specifically, gait datasets are collected by the triaxial accelerometer and gyrometer embedded in an iPhone. Then, the datasets are processed to extract gait characteristic parameters which include gait frequency, symmetry coefficient, dynamic range and similarity coefficient of characteristic curves. Finally, a weighted voting scheme dependent upon the gait characteristic parameters is proposed forgait identification. Four experiments are implemented to validate the proposed scheme. The attitude and acceleration solutions are verified by simulation. Then the gait characteristics are analyzed by comparing two sets of actual data, and the performance of the weighted voting identification scheme is verified by 40 datasets of 10 subjects.

  18. MEMS加速度计的六位置测试法%Six-Position Testing of MEMS Accelerometer

    Institute of Scientific and Technical Information of China (English)

    宋丽君; 秦永元

    2009-01-01

    主要介绍了MEMS加速度计的六位置测试法,根据MEMS加速度计输出数学模型详细推导了如何得到MEMS加速度计的输出数学模型中的刻度因数、零偏以及安装误差,并在得到其标定系数后将其封装在C函数中进行了验证实验.通过实验数据分析可知,MEMS加速度计的六位置测试法原理简单、易于实现,且精度较高.这种标定法所得到的MEMS加速度计输出能够比较准确地反映其输出,而且MEMS加速度计的线性度有所改善.%A six-position testing method of MEMS accelerometer is introduced mainly. According to the error model of MEMS accelerometer the scale factor of MEMS accelerometer, bias of MEMS accelerometer and error on installation of MEMS accelerometer are derived. When the user gets these parameters, the user should pack the function of the concrete mathematics model in C code. By analyzing the results of examination, the six-posi-tion testing method of MEMS accelerometer is simple on principle, easy to realize and high in precision as long as the user gets the error model of MEMS accelerometer. And the scale factor nonlinearity is improved by the error model of MEMS accelerometer.

  19. Accuracy of StepWatch™ and ActiGraph Accelerometers for Measuring Steps Taken among Persons with Multiple Sclerosis

    OpenAIRE

    Brian M. Sandroff; Motl, Robert W.; Pilutti, Lara A.; Learmonth, Yvonne C.; Ipek Ensari; Deirdre Dlugonski; Klaren, Rachel E; Swathi Balantrapu; Barry J Riskin

    2014-01-01

    INTRODUCTION: There has been increased interest in the objective monitoring of free-living walking behavior using accelerometers in clinical research involving persons with multiple sclerosis (MS). The current investigation examined and compared the accuracy of the StepWatch activity monitor and ActiGraph model GT3X+ accelerometer for capturing steps taken during various speeds of prolonged, over-ground ambulation in persons with MS who had mild, moderate, and severe disability. METHODS: Sixt...

  20. Application of MAVEN Accelerometer and Attitude Control Data to Mars Atmospheric Characterization

    Science.gov (United States)

    Zurek, Richard W.; Tolson, Robert H.; Baird, Darren; Johnson, Mark Z.; Bougher, Stephen W.

    2015-12-01

    The structure of the upper atmosphere of Mars (above ˜100 km) has been probed in situ mainly using spacecraft accelerometers during the aerobraking phases of 3 Mars orbiters. In a similar manner, the Mars Atmosphere and Volatile Evolution (MAVEN) Accelerometer Experiment (ACC) will also use atmospheric drag accelerations sensed by inertial measurement units (IMU) onboard the spacecraft to recover atmospheric density along the orbiter path. These densities are used to estimate hydrostatic `vertical' density and temperature profiles, along track and altitudinal density waves, and latitudinal and longitudinal density variations. The IMU accelerometer signal-to-noise should permit profile reconstructions from spacecraft periapsis, nominally at 150 km altitude, to ˜170 km, an altitude range nominally spanning densities of 0.05-0.15 kg/km3. However, in situ measurements over a much greater altitude range, down to ˜125 km (reaching densities of ˜2-3.5 kg/km3), can be made during each of five week-long "Deep Dip" (DD) campaigns, and these are the prime focus of the Accelerometer Experiment. Judicious choice of the timing of these Deep-Dip campaigns during the MAVEN periapsis progression through local time, latitude and longitude in both hemispheres and in different seasons will add significantly to the existing data base of lower thermospheric densities. Other IMU and attitude control data may be used to estimate torques in order to improve the atmospheric density analysis, especially in the higher altitudes of the nominal science orbit, and, more challengingly, to estimate cross-track winds during the Deep-Dips.

  1. An eHealth System for Pressure Ulcer Risk Assessment Based on Accelerometer and Pressure Data

    OpenAIRE

    Dieter Hayn; Markus Falgenhauer; Jürgen Morak; Karin Wipfler; Viktoria Willner; Walter Liebhart; Günter Schreier

    2015-01-01

    Pressure ulcers are a common skin disease which is associated with pain, reduced autonomy, social isolation, and reduced quality of life. There are several systems for monitoring of pressure ulcer-related risk factors on the market, but up to now no satisfactory solution is available, especially for people with medium pressure ulcer risk. We present a novel pressure ulcer risk assessment and prevention system, which combines the advantages of accelerometer and pressure sensors for monitoring ...

  2. Comparison of equations for predicting energy expenditure from accelerometer counts in children

    DEFF Research Database (Denmark)

    Nilsson, A; Brage, S; Riddoch, C;

    2008-01-01

    sample of children. We examined 1321 children (663 boys, 658 girls; mean age 9.6+/-0.4 years) from four different countries. Physical activity was measured by the MTI accelerometer. One equation, derived from doubly labeled water (DLW) measurements, was compared with one treadmill-based (TM) and one room......, and interpretations of average levels of PAEE in children from available equations should be made with caution. Further development of equations applicable to free-living scenarios is needed....

  3. A novel capacitive micro-accelerometer with grid strip capacitances and sensing gap alterable capacitances

    Institute of Scientific and Technical Information of China (English)

    Dong Linxi; Chen Jindan; Yan Haixia; Huo Weihong; Li Yongjie; Sun Lingling

    2009-01-01

    The comb capacitances fabricated by deep reactive ion etching (RIE) process have high aspect ratio which is usually smaller than 30 : 1 for the complicated process factors, and the combs are usually not parallel due to the well-known micro-loading effect and other process factors, which restricts the increase of the seismic mass by increasing the thickness of comb to reduce the thermal mechanical noise and the decrease of the gap of the comb capacitances for increasing the sensitive capacitance to reduce the electrical noise. Aiming at the disadvantage of the deep RIE, a novel capacitive micro-accelerometer with grid strip capacitances and sensing gap alterable capacitances is developed. One part of sensing of inertial signal of the micro-accelerometer is by the grid strip capacitances whose overlapping area is variable and which do not have the non-parallel plate's effect caused by the deep RIE process. Another part is by the sensing gap alterable capacitances whose gap between combs can be reduced by the actuators. The designed initial gap of the alterable comb capacitances is relatively large to depress the effect of the maximum aspect ratio (30 : 1) of deep RIE process. The initial gap of the capacitance of the actuator is smaller than the one of the comb capacitances. The difference between the two gaps is the initial gap of the sensitive capacitor. The designed structure depresses greatly the requirement of deep RIE process. The effects of non-parallel combs on the accelerometer are also analyzed. The characteristics of the micro-accelerometer are discussed by field emission microscopy (FEM) tool ANSYS. The tested devices based on slide-film damping effect are fabricated, and the tested quality factor is 514, which shows that grid strip capacitance design can partly improve the resolution and also prove the feasibility of the designed silicon-glass anodically bonding process.

  4. Electrostatic accelerometer with bias rejection for Gravitation and Solar System physics

    OpenAIRE

    Lenoir, Benjamin; Lévy, Agnès; Foulon, Bernard; Lamine, Brahim; Christophe, Bruno; Reynaud, Serge

    2010-01-01

    Radio tracking of interplanetary probes is an important tool for navigation purposes as well as for testing the laws of physics or exploring planetary environments. The addition of an accelerometer on board a spacecraft provides orbit determination specialists and physicists with an additional observable of great interest: it measures the value of the non-gravitational acceleration acting on the spacecraft, i.e. the departure of the probe from geodesic motion. This technology is now routinely...

  5. Theory, technology and assembly of a highly symmetrical capacitive triaxial accelerometer

    OpenAIRE

    Lotters, J.C.; Olthuis, W.; Veltink, P.H.; Bergveld, P.

    1997-01-01

    A highly symmetrical cubic easy-to-assemble capacitive triaxial accelerometer for biomedical applications has been designed, realized and tested. The outer dimensions of the sensor are 5×5×5 mm 3 and the device is mounted on a standard IC package. New aspects of the sensor are an easy assembly procedure, the use of the polymers polydimethylsiloxane (PDMS) as spring material between the capacitor plates and the mass and polyimide (PI) as flexible interconnection layer between the capacitor pla...

  6. Self-Locking Avoidance and Stiffness Compensation of a Three-Axis Micromachined Electrostatically Suspended Accelerometer

    OpenAIRE

    Yonggang Yin; Boqian Sun; Fengtian Han

    2016-01-01

    A micromachined electrostatically-suspended accelerometer (MESA) is a kind of three-axis inertial sensor based on fully-contactless electrostatic suspension of the proof mass (PM). It has the potential to offer broad bandwidth, high sensitivity, wide dynamic range and, thus, would be perfectly suited for land seismic acquisition. Previous experiments showed that it is hard to lift up the PM successfully during initial levitation as the mass needs to be levitated simultaneously in all six degr...

  7. Quality of GOCE accelerometer data and analysis with ionospheric dynamics during geomagnetically active days

    Science.gov (United States)

    Sinem Ince, Elmas; Fomichev, Victor; Floberghagen, Rune; Schlicht, Anja; Martynenko, Oleg; Pagiatakis, Spiros

    2016-07-01

    The Gravity field and steady-state Ocean Circulation Explorer (GOCE) was launched in March, 2009 and completed its mission with great success in November, 2011. GOCE data processing is challenging and not all the disturbances are removed from the gravitational field observations. The disturbances observed in GOCE Vyy gradients around magnetic poles are investigated by using external datasets. It is found that the amplitude of these disturbances increase during geomagnetically active days and can reach up to 5 times the expected noise level of the gradiometer. ACE (Advanced Composition Explorer) and Wind satellites measured electric field and interplanetary magnetic field components have shown that the disturbances observed in the polar regions agree with the increased solar activity. Moreover, equivalent ionospheric currents computed along ascending satellite tracks over North America and Greenland have shown a noticeable correlation with the cross-track and vertical currents and the pointing flux (ExB) components in the satellite cross track direction. Lastly, Canadian Ionosphere and Atmosphere Model (C-IAM) electric field and neutral wind simulations have shown a strong correlation of the enhancement in the ionospheric dynamics during geomagnetically active days and disturbances measured by the GOCE accelerometers over high latitudes. This may be a result of imperfect instrumentation and in-flight calibration of the GOCE accelerometers for an increased geomagnetic activity or a real disturbance on the accelerometers. We use above listed external datasets to understand the causes of the disturbances observed in gravity gradients and reduce/ eliminate them by using response analyses in frequency domain. Based on our test transfer functions, improvement is possible in the quality of the gradients. Moreover, this research also confirms that the accelerometer measurements can be useful to understand the ionospheric dynamics and space weather forecasting.

  8. Detecting Fetal Movements Using Non-Invasive Accelerometers: A Preliminary Analysis

    OpenAIRE

    Girier, T.; O'Toole, J; Mesbah, M.; Boashash, B.; Clough, I.; Wilson, S; Fuentes, M; Callan, S.; East, C; COLDITZ, P

    2010-01-01

    Monitoring fetal movement is important to assess fetal health. Standard clinical fetal monitoring technologies include ultrasound imaging and cardiotocography. Both have limited prognostic value and require significant health resources. We have recently developed a low-cost, passive, non-invasive system to monitor fetal activity, and therefore fetal health. This accelerometer-based system does not require trained operators and can be used outside a clinic. This work is a preliminary study to ...

  9. Non-Parametric Bayesian Human Motion Recognition Using a Single MEMS Tri-Axial Accelerometer

    OpenAIRE

    Ejaz Ahmed, M.; Ju Bin Song

    2012-01-01

    In this paper, we propose a non-parametric clustering method to recognize the number of human motions using features which are obtained from a single microelectromechanical system (MEMS) accelerometer. Since the number of human motions under consideration is not known a priori and because of the unsupervised nature of the proposed technique, there is no need to collect training data for the human motions. The infinite Gaussian mixture model (IGMM) and collapsed Gibbs sampler are adopted to cl...

  10. Pyroshock data acquisition-historical developments using piezoelectric accelerometers and other transducers

    Science.gov (United States)

    Himelblau, Harry

    2002-05-01

    For nearly 50 years, P/E accelerometers have been used for acquiring pyroshock data with mixed results. For longer distances between the explosive source and the transducer location (e.g., two feet or more), valid data of lesser shock magnitude were usually obtained. However, for shorter distances, a variety of problems were often encountered, causing erroneous results. It was subsequentially determined that most problems were caused by measurement system nonlinearities, i.e., the nonlinear resonant response of the accelerometer, or exceeding the linear amplitude range of the signal conditioner and recorder. In the earlier years, it was erroneously assumed that subsequent low pass filtering of the signal would remove the nonlinearities, hopefully leading to valid data. This only masked the invalid results. Eventually, improved P/E accelerometers were developed with higher natural frequencies and larger amplitude limits that caused substantially fewer problems and allowed measurements closer to the explosive sources. Shortly thereafter, the high frequency noncontact laser doppler vibrometer became available which circumvented the accelerometer resonance problem. However, this velocity transducer is almost always limited to laboratory tests in order to constrain the motion of the laser head by a very rigid and massive support foundation compared to the flexible structure which is attached to the laser target. Other LDV measurement problems have been encountered that must be avoided to achieve valid data. Conventional strain gages have been successfully used to measure pyroshock strain. However, due to the short wavelength of direct and bending pyroshock waves at high frequencies, small strain gages are usually required to avoid spatial averaging over the length of the gage.

  11. Design, Fabrication and Levitation Experiments of a Micromachined Electrostatically Suspended Six-Axis Accelerometer

    OpenAIRE

    Weiping Zhang; Xiaosheng Wu; Wenyuan Chen; Wu Liu; Feng Cui

    2011-01-01

    A micromachined electrostatically suspended six-axis accelerometer, with a square plate as proof mass housed by a top stator and bottom stator, is presented. The device structure and related techniques concerning its operating principles, such as calculation of capacitances and electrostatic forces/moments, detection and levitation control of the proof mass, acceleration measurement, and structural parameters design, are described. Hybrid MEMS manufacturing techniques, including surface micro...

  12. Using accelerometers to determine the calling behavior of tagged baleen whales

    OpenAIRE

    Goldbogen, J.A.; Stimpert, A. K.; DeRuiter, S. L.; Calambokidis, J.; Friedlaender, A.S.; G. S. Schorr; Moretti, D. J.; Tyack, P.L.; Southall, B.L.

    2014-01-01

    The article of record as published may be found at http://dx.doi.org/10.1242/jeb.103259 Low-frequency acoustic signals generated by baleen whales can propagate over vast distances, making the assignment of calls to specific individuals problematic. Here, we report the novel use of acoustic recording tags equipped with high-resolution accelerometers to detect vibrations from the surface of two tagged fin whales that directly match the timing of recorded acoustic signals. A ta...

  13. Using Hidden Markov Models to Improve Quantifying Physical Activity in Accelerometer Data – A Simulation Study

    Science.gov (United States)

    Witowski, Vitali; Foraita, Ronja; Pitsiladis, Yannis; Pigeot, Iris; Wirsik, Norman

    2014-01-01

    Introduction The use of accelerometers to objectively measure physical activity (PA) has become the most preferred method of choice in recent years. Traditionally, cutpoints are used to assign impulse counts recorded by the devices to sedentary and activity ranges. Here, hidden Markov models (HMM) are used to improve the cutpoint method to achieve a more accurate identification of the sequence of modes of PA. Methods 1,000 days of labeled accelerometer data have been simulated. For the simulated data the actual sedentary behavior and activity range of each count is known. The cutpoint method is compared with HMMs based on the Poisson distribution (HMM[Pois]), the generalized Poisson distribution (HMM[GenPois]) and the Gaussian distribution (HMM[Gauss]) with regard to misclassification rate (MCR), bout detection, detection of the number of activities performed during the day and runtime. Results The cutpoint method had a misclassification rate (MCR) of 11% followed by HMM[Pois] with 8%, HMM[GenPois] with 3% and HMM[Gauss] having the best MCR with less than 2%. HMM[Gauss] detected the correct number of bouts in 12.8% of the days, HMM[GenPois] in 16.1%, HMM[Pois] and the cutpoint method in none. HMM[GenPois] identified the correct number of activities in 61.3% of the days, whereas HMM[Gauss] only in 26.8%. HMM[Pois] did not identify the correct number at all and seemed to overestimate the number of activities. Runtime varied between 0.01 seconds (cutpoint), 2.0 minutes (HMM[Gauss]) and 14.2 minutes (HMM[GenPois]). Conclusions Using simulated data, HMM-based methods were superior in activity classification when compared to the traditional cutpoint method and seem to be appropriate to model accelerometer data. Of the HMM-based methods, HMM[Gauss] seemed to be the most appropriate choice to assess real-life accelerometer data. PMID:25464514

  14. MOCA: A Low-Power, Low-Cost Motion Capture System Based on Integrated Accelerometers

    Directory of Open Access Journals (Sweden)

    Elisabetta Farella

    2007-01-01

    Full Text Available Human-computer interaction (HCI and virtual reality applications pose the challenge of enabling real-time interfaces for natural interaction. Gesture recognition based on body-mounted accelerometers has been proposed as a viable solution to translate patterns of movements that are associated with user commands, thus substituting point-and-click methods or other cumbersome input devices. On the other hand, cost and power constraints make the implementation of a natural and efficient interface suitable for consumer applications a critical task. Even though several gesture recognition solutions exist, their use in HCI context has been poorly characterized. For this reason, in this paper, we consider a low-cost/low-power wearable motion tracking system based on integrated accelerometers called motion capture with accelerometers (MOCA that we evaluated for navigation in virtual spaces. Recognition is based on a geometric algorithm that enables efficient and robust detection of rotational movements. Our objective is to demonstrate that such a low-cost and a low-power implementation is suitable for HCI applications. To this purpose, we characterized the system from both a quantitative point of view and a qualitative point of view. First, we performed static and dynamic assessment of movement recognition accuracy. Second, we evaluated the effectiveness of user experience using a 3D game application as a test bed.

  15. Application of MEMS Accelerometers and Gyroscopes in Fast Steering Mirror Control Systems.

    Science.gov (United States)

    Tian, Jing; Yang, Wenshu; Peng, Zhenming; Tang, Tao; Li, Zhijun

    2016-01-01

    In a charge-coupled device (CCD)-based fast steering mirror (FSM) tracking control system, high control bandwidth is the most effective way to enhance the closed-loop performance. However, the control system usually suffers a great deal from mechanical resonances and time delays induced by the low sampling rate of CCDs. To meet the requirements of high precision and load restriction, fiber-optic gyroscopes (FOGs) are usually used in traditional FSM tracking control systems. In recent years, the MEMS accelerometer and gyroscope are becoming smaller and lighter and their performance have improved gradually, so that they can be used in a fast steering mirror (FSM) to realize the stabilization of the line-of-sight (LOS) of the control system. Therefore, a tentative approach to implement a CCD-based FSM tracking control system, which uses MEMS accelerometers and gyroscopes as feedback components and contains an acceleration loop, a velocity loop and a position loop, is proposed. The disturbance suppression of the proposed method is the product of the error attenuation of the acceleration loop, the velocity loop and the position loop. Extensive experimental results show that the MEMS accelerometers and gyroscopes can act the similar role as the FOG with lower cost for stabilizing the LOS of the FSM tracking control system.

  16. The use of an unsupervised learning approach for characterizing latent behaviors in accelerometer data.

    Science.gov (United States)

    Chimienti, Marianna; Cornulier, Thomas; Owen, Ellie; Bolton, Mark; Davies, Ian M; Travis, Justin M J; Scott, Beth E

    2016-02-01

    The recent increase in data accuracy from high resolution accelerometers offers substantial potential for improved understanding and prediction of animal movements. However, current approaches used for analysing these multivariable datasets typically require existing knowledge of the behaviors of the animals to inform the behavioral classification process. These methods are thus not well-suited for the many cases where limited knowledge of the different behaviors performed exist. Here, we introduce the use of an unsupervised learning algorithm. To illustrate the method's capability we analyse data collected using a combination of GPS and Accelerometers on two seabird species: razorbills (Alca torda) and common guillemots (Uria aalge). We applied the unsupervised learning algorithm Expectation Maximization to characterize latent behavioral states both above and below water at both individual and group level. The application of this flexible approach yielded significant new insights into the foraging strategies of the two study species, both above and below the surface of the water. In addition to general behavioral modes such as flying, floating, as well as descending and ascending phases within the water column, this approach allowed an exploration of previously unstudied and important behaviors such as searching and prey chasing/capture events. We propose that this unsupervised learning approach provides an ideal tool for the systematic analysis of such complex multivariable movement data that are increasingly being obtained with accelerometer tags across species. In particular, we recommend its application in cases where we have limited current knowledge of the behaviors performed and existing supervised learning approaches may have limited utility.

  17. Flight experience on CHAMP and GRACE with ultra-sensitive accelerometers and return for LISA

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Manuel; Foulon, Bernard; Liorzou, Francoise; Touboul, Pierre [Physics and Instrumentation Department, Office National d' Etudes et de Recherches Aerospatiales, BP 72, 92322 Chatillon Cedex (France)

    2003-05-21

    The challenging drag-free sensor of the Laser Interferometer Space Antenna (LISA) mission is derived from electrostatic accelerometers developed for a long time in ONERA. The LISA sensor includes a gold platinum alloy inertial mass free-floating in space and used as reflectors for the laser interferometer. This test mass should not undergo more than 3x10{sup -15} m s{sup -2} Hz{sup -1/2} acceleration at 0.1 mHz. This tremendous performance is not close to what has been reached so far, but should be approached within one order of magnitude with the projected SMART-2 ESA mission by 2006. Meanwhile, ONERA has participated in several space missions with the flight of increasingly sensitive accelerometers. The German CHAMP mission aims at mapping the Earth's magnetic and gravity fields. More than two years data have been accumulated showing a resolution better than 3 x 10{sup -9} m s{sup -2} Hz{sup -1/2} for the accelerometer. With the JPL/NASA GRACE mission launched in March 2002, even more sensitive measurements have been obtained. From these two flight experiments with electrostatic sensors very similar in concept to that of LISA, the accelerometric environment on board a satellite is discussed at nanogravity levels. It is also shown that these first analyses are compatible with the expected LISA performance when the results are extrapolated to the LISA environment, needing femto-gravity levels.

  18. Measurement Model and Precision Analysis of Accelerometers for Maglev Vibration Isolation Platforms

    Directory of Open Access Journals (Sweden)

    Qianqian Wu

    2015-08-01

    Full Text Available High precision measurement of acceleration levels is required to allow active control for vibration isolation platforms. It is necessary to propose an accelerometer configuration measurement model that yields such a high measuring precision. In this paper, an accelerometer configuration to improve measurement accuracy is proposed. The corresponding calculation formulas of the angular acceleration were derived through theoretical analysis. A method is presented to minimize angular acceleration noise based on analysis of the root mean square noise of the angular acceleration. Moreover, the influence of installation position errors and accelerometer orientation errors on the calculation precision of the angular acceleration is studied. Comparisons of the output differences between the proposed configuration and the previous planar triangle configuration under the same installation errors are conducted by simulation. The simulation results show that installation errors have a relatively small impact on the calculation accuracy of the proposed configuration. To further verify the high calculation precision of the proposed configuration, experiments are carried out for both the proposed configuration and the planar triangle configuration. On the basis of the results of simulations and experiments, it can be concluded that the proposed configuration has higher angular acceleration calculation precision and can be applied to different platforms.

  19. Lumped parameter analytic modeling and behavioral simulation of a 3-DOF MEMS gyro-accelerometer

    Science.gov (United States)

    Verma, Payal; Arya, Sandeep K.; Gopal, Ram

    2015-12-01

    A new analytical model of a 3-degree-of-freedom (3-DOF) gyro-accelerometer system consisting of a 1-DOF drive and 2-DOF sense modes is presented. The model constructs lumped differential equations associated with each DOF of the system by vector analysis. The coupled differential equations thus established are solved analytically for their responses in both the time and frequency domains. Considering these frequency response equations, novel device design concepts are derived by forcing the sense phase to zero, which leads to a certain relationship between the structural frequencies, thereby causing minimization of the damping effect on the performance of the system. Furthermore, the feasibility of the present gyro-accelerometer structure is studied using a unique discriminatory scheme for the detection of both gyro action and linear acceleration at their events. This scheme combines the formulated settled transient solution of the gyro-accelerometer with the processes of synchronous demodulation and filtration, which leads to the in-phase and quadrature components of the system's output signal. These two components can be utilized in the detection of angular motion and linear acceleration. The obtained analytical results are validated by simulation in a MATLAB/Simulink environment, and it is found that the results are in excellent agreement with each other.

  20. Accelerometer and gyroscope based gait analysis using spectral analysis of patients with osteoarthritis of the knee.

    Science.gov (United States)

    Staab, Wieland; Hottowitz, Ralf; Sohns, Christian; Sohns, Jan Martin; Gilbert, Fabian; Menke, Jan; Niklas, Andree; Lotz, Joachim

    2014-07-01

    [Purpose] A wide variety of accelerometer tools are used to estimate human movement, but there are no adequate data relating to gait symmetry parameters in the context of knee osteoarthritis. This study's purpose was to evaluate a 3D-kinematic system using body-mounted sensors (gyroscopes and accelerometers) on the trunk and limbs. This is the first study to use spectral analysis for data post processing. [Subjects] Twelve patients with unilateral knee osteoarthritis (OA) (10 male) and seven age-matched controls (6 male) were studied. [Methods] Measurements with 3-D accelerometers and gyroscopes were compared to video analysis with marker positions tracked by a six-camera optoelectronic system (VICON 460, Oxford Metrics). Data were recorded using the 3D-kinematic system. [Results] The results of both gait analysis systems were significantly correlated. Five parameters were significantly different between the knee OA and control groups. To overcome time spent in expensive post-processing routines, spectral analysis was performed for fast differentiation between normal gait and pathological gait signals using the 3D-kinematic system. [Conclusions] The 3D-kinematic system is objective, inexpensive, accurate and portable, and allows long-term recordings in clinical, sport as well as ergonomic or functional capacity evaluation (FCE) settings. For fast post-processing, spectral analysis of the recorded data is recommended.

  1. Design and analysis of a novel virtual gyroscope with multi-gyroscope and accelerometer array

    Science.gov (United States)

    Luo, Zhang; Liu, Chaojun; Yu, Shuai; Zhang, Shengzhi; Liu, Sheng

    2016-08-01

    A new virtual gyroscope with multi-gyroscope and accelerometer array (MGAA) is proposed in this article for improving the performance of angular rate measurement. Outputs of the virtual gyroscope are obtained by merging the signals from gyroscopes and accelerometers through a novel Kalman filter, which intentionally takes the consideration of the MEMS gyroscope error model and kinematics theory of rigid body. A typical configuration of the virtual gyroscope, consisting of four accelerometers and three gyroscopes mounted on designated positions, is initiated to verify the feasibility of the virtual gyroscope with MGAA. Static test and dynamic test are performed subsequently to evaluate its performance. The angular random walk (ARW) and bias instability, two static performance parameters of gyroscope, are reduced from 0.019°/√s and 14.4°/h to 0.0074°/√s and 8.7°/h, respectively. The average root mean square error (RMSE) is reduced from 0.274°/s to 0.133°/s under dynamic test. Compared with the published multi-gyroscope array method, the virtual gyroscope proposed here has a better performance both in static and dynamic tests, with improvement factors of ARW and RMSE about 44.1% and 44.5% higher, respectively.

  2. Measurement Model and Precision Analysis of Accelerometers for Maglev Vibration Isolation Platforms.

    Science.gov (United States)

    Wu, Qianqian; Yue, Honghao; Liu, Rongqiang; Zhang, Xiaoyou; Ding, Liang; Liang, Tian; Deng, Zongquan

    2015-01-01

    High precision measurement of acceleration levels is required to allow active control for vibration isolation platforms. It is necessary to propose an accelerometer configuration measurement model that yields such a high measuring precision. In this paper, an accelerometer configuration to improve measurement accuracy is proposed. The corresponding calculation formulas of the angular acceleration were derived through theoretical analysis. A method is presented to minimize angular acceleration noise based on analysis of the root mean square noise of the angular acceleration. Moreover, the influence of installation position errors and accelerometer orientation errors on the calculation precision of the angular acceleration is studied. Comparisons of the output differences between the proposed configuration and the previous planar triangle configuration under the same installation errors are conducted by simulation. The simulation results show that installation errors have a relatively small impact on the calculation accuracy of the proposed configuration. To further verify the high calculation precision of the proposed configuration, experiments are carried out for both the proposed configuration and the planar triangle configuration. On the basis of the results of simulations and experiments, it can be concluded that the proposed configuration has higher angular acceleration calculation precision and can be applied to different platforms. PMID:26287203

  3. Physical Explanation on Designing Three Axes as Different Resolution Indexes from GRACE Satellite-Borne Accelerometer

    Institute of Scientific and Technical Information of China (English)

    ZHENG Wei; XU Hou-Ze; ZHONG Min; YUN Mei-Juan

    2008-01-01

    @@ The GRACE Earth's gravitational field complete up to degree and order 120 is recovered based on the same and different three-axis resolution indexes from satellite-borne accelerometer using the improved energy conservation principle. The results show that designing XA1(2) as low-sensitivity axis (3 × 10-9 m/s2) of accelerometer and designing YA1(2) and ZA1(2) as high-sensitivity axes (3 × 10-10m/s2) are reasonable. The physical reason why the resolution of XA1(2) is one order of magnitude lower than YA1(2) and ZA1(2) is that non-conservative forces acting on GRACE satellites axe mainly decomposed into YA1(2) and ZA1(2) in the orbital plane.Since X A1(2) is not orthogonal accurately to orbital plane during the development of accelerometer, the measurement of X A1(2) can not be thrown off entirely, but be reduced properly.

  4. A wafer level vacuum encapsulated capacitive accelerometer fabricated in an unmodified commercial MEMS process.

    Science.gov (United States)

    Merdassi, Adel; Yang, Peng; Chodavarapu, Vamsy P

    2015-01-01

    We present the design and fabrication of a single axis low noise accelerometer in an unmodified commercial MicroElectroMechanical Systems (MEMS) process. The new microfabrication process, MEMS Integrated Design for Inertial Sensors (MIDIS), introduced by Teledyne DALSA Inc. allows wafer level vacuum encapsulation at 10 milliTorr which provides a high Quality factor and reduces noise interference on the MEMS sensor devices. The MIDIS process is based on high aspect ratio bulk micromachining of single-crystal silicon layer that is vacuum encapsulated between two other silicon handle wafers. The process includes sealed Through Silicon Vias (TSVs) for compact design and flip-chip integration with signal processing circuits. The proposed accelerometer design is sensitive to single-axis in-plane acceleration and uses a differential capacitance measurement. Over ±1 g measurement range, the measured sensitivity was 1 fF/g. The accelerometer system was designed to provide a detection resolution of 33 milli-g over the operational range of ±100 g. PMID:25815451

  5. A Wafer Level Vacuum Encapsulated Capacitive Accelerometer Fabricated in an Unmodified Commercial MEMS Process

    Directory of Open Access Journals (Sweden)

    Adel Merdassi

    2015-03-01

    Full Text Available We present the design and fabrication of a single axis low noise accelerometer in an unmodified commercial MicroElectroMechanical Systems (MEMS process. The new microfabrication process, MEMS Integrated Design for Inertial Sensors (MIDIS, introduced by Teledyne DALSA Inc. allows wafer level vacuum encapsulation at 10 milliTorr which provides a high Quality factor and reduces noise interference on the MEMS sensor devices. The MIDIS process is based on high aspect ratio bulk micromachining of single-crystal silicon layer that is vacuum encapsulated between two other silicon handle wafers. The process includes sealed Through Silicon Vias (TSVs for compact design and flip-chip integration with signal processing circuits. The proposed accelerometer design is sensitive to single-axis in-plane acceleration and uses a differential capacitance measurement. Over ±1 g measurement range, the measured sensitivity was 1fF/g. The accelerometer system was designed to provide a detection resolution of 33 milli-g over the operational range of ±100 g.

  6. Application of MEMS Accelerometers and Gyroscopes in Fast Steering Mirror Control Systems

    Directory of Open Access Journals (Sweden)

    Jing Tian

    2016-03-01

    Full Text Available In a charge-coupled device (CCD-based fast steering mirror (FSM tracking control system, high control bandwidth is the most effective way to enhance the closed-loop performance. However, the control system usually suffers a great deal from mechanical resonances and time delays induced by the low sampling rate of CCDs. To meet the requirements of high precision and load restriction, fiber-optic gyroscopes (FOGs are usually used in traditional FSM tracking control systems. In recent years, the MEMS accelerometer and gyroscope are becoming smaller and lighter and their performance have improved gradually, so that they can be used in a fast steering mirror (FSM to realize the stabilization of the line-of-sight (LOS of the control system. Therefore, a tentative approach to implement a CCD-based FSM tracking control system, which uses MEMS accelerometers and gyroscopes as feedback components and contains an acceleration loop, a velocity loop and a position loop, is proposed. The disturbance suppression of the proposed method is the product of the error attenuation of the acceleration loop, the velocity loop and the position loop. Extensive experimental results show that the MEMS accelerometers and gyroscopes can act the similar role as the FOG with lower cost for stabilizing the LOS of the FSM tracking control system.

  7. A novel quasi-digital detection method of micro differential capacitance in micro-accelerometers

    Science.gov (United States)

    Song, Xing; Fang, Jiancheng; Yi, Ranran; Sheng, Wei

    2008-10-01

    This paper proposed a novel method of sensing the weak differential capacitance change of Micro-Electro-Mechanical Systems (MEMS) accelerometer with sandwich structure. The detection circuit mainly consisted of frequency selective networks, Phase Locked Loop (PLL), logical gate and low-pass filter. The two elemental capacitances of differential capacitance respectively harmonic oscillated in two parameter symmetry resonance units. Beating wave represented when the two output signals with different frequency had passed the logical gate and low-pass filter in turn. The frequency of beating wave was proportional to the sensing differential capacitance. One of the most important aspects of using circuit resonance elements with MEMS technology was the elimination of analog voltage amplitude measurement used in conventional MEMS accelerometers. On the other hand, this method overcame the disadvantages of conventional mechanical resonance accelerometers, with frequency output and high Signal Noise Ratio (SNR), such as poor dynamic response, temperature drift, complex structure and large power dissipation. According to the numerical simulation results, the circuit resonance detector with PLL can reach high capacitance resolution: 10-16 F.

  8. Identifying active travel behaviors in challenging environments using GPS, accelerometers and machine learning algorithms

    Directory of Open Access Journals (Sweden)

    Katherine eEllis

    2014-04-01

    Full Text Available Background: Active travel is an important area in physical activity research, but objective measurement of active travel is still difficult. Automated methods to measure travel behaviors will improve research in this area. In this paper we present a supervised machine learning method for transportation mode prediction from GPS and accelerometer data. Methods: We collected a dataset of about 150 hours of GPS and accelerometer data from two research assistants following a protocol of prescribed trips consisting of five activities: bicycling, riding in a vehicle, walking, sitting, and standing. We extracted 49 features from 1-minute windows of this data. We compared the performance of several machine learning algorithms and chose a random forest algorithm to classify the transportation mode. We used a moving average output filter to smooth the output predictions over time. Results: The random forest algorithm achieved 89.8% cross-validated accuracy on this dataset. Adding the moving average filter to smooth output predictions increased the cross-validated accuracy to 91.9%. Conclusions: Machine learning methods are a viable approach for automating measurement of active travel, particularly for measuring travel activities that traditional accelerometer data processing methods misclassify, such as bicycling and vehicle travel.

  9. Design and experimental research on cantilever accelerometer based on fiber Bragg grating

    Science.gov (United States)

    Xiang, Longhai; Jiang, Qi; Li, Yibin; Song, Rui

    2016-06-01

    Currently, an acceleration sensor based on fiber Bragg grating (FBG) has been widely used. A cantilever FBG accelerometer is designed. The simulation of this structure was implemented by finite element software (ANSYS) to analyze its sensing performance parameters. And then the optimized structure was produced and calibration experiments were conducted. On the basis of simulation, optical fiber is embedded in the inner tank of the vibrating mass, and Bragg grating is suspended above the cantilever structure, which can effectively avoid the phenomenon of center wavelength chirp or broadening, and greatly improve the sensitivity of the sensor. The experimental results show that the FBG accelerometer exhibits a sensitivity of 75 pm/(m/s2) (100 Hz) and dynamic range of 60 dB. Its linearity error is <2.31% and repeatability error is <2.76%. And the resonant frequency is ˜125 Hz. The simulation results match the experimental results to demonstrate the good performance of FBG accelerometer, which is expected to be used in the actual project.

  10. Improving the Response of Accelerometers for Automotive Applications by Using LMS Adaptive Filters: Part II

    Directory of Open Access Journals (Sweden)

    Eduardo Fernández

    2010-01-01

    Full Text Available In this paper, the fast least-mean-squares (LMS algorithm was used to both eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications, and improve the convergence rate of the filtering process based on the conventional LMS algorithm. The response of the accelerometer under test was corrupted by process and measurement noise, and the signal processing stage was carried out by using both conventional filtering, which was already shown in a previous paper, and optimal adaptive filtering. The adaptive filtering process relied on the LMS adaptive filtering family, which has shown to have very good convergence and robustness properties, and here a comparative analysis between the results of the application of the conventional LMS algorithm and the fast LMS algorithm to solve a real-life filtering problem was carried out. In short, in this paper the piezoresistive accelerometer was tested for a multi-frequency acceleration excitation. Due to the kind of test conducted in this paper, the use of conventional filtering was discarded and the choice of one adaptive filter over the other was based on the signal-to-noise ratio improvement and the convergence rate.

  11. Improving the response of accelerometers for automotive applications by using LMS adaptive filters: Part II.

    Science.gov (United States)

    Hernandez, Wilmar; de Vicente, Jesús; Sergiyenko, Oleg Y; Fernández, Eduardo

    2010-01-01

    In this paper, the fast least-mean-squares (LMS) algorithm was used to both eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications, and improve the convergence rate of the filtering process based on the conventional LMS algorithm. The response of the accelerometer under test was corrupted by process and measurement noise, and the signal processing stage was carried out by using both conventional filtering, which was already shown in a previous paper, and optimal adaptive filtering. The adaptive filtering process relied on the LMS adaptive filtering family, which has shown to have very good convergence and robustness properties, and here a comparative analysis between the results of the application of the conventional LMS algorithm and the fast LMS algorithm to solve a real-life filtering problem was carried out. In short, in this paper the piezoresistive accelerometer was tested for a multi-frequency acceleration excitation. Due to the kind of test conducted in this paper, the use of conventional filtering was discarded and the choice of one adaptive filter over the other was based on the signal-to-noise ratio improvement and the convergence rate. PMID:22315579

  12. Attitude Determination with Magnetometers and Accelerometers to Use in Satellite Simulator

    Directory of Open Access Journals (Sweden)

    Helio Koiti Kuga

    2013-01-01

    Full Text Available Attitude control of artificial satellites is dependent on information provided by its attitude determination process. This paper presents the implementation and tests of a fully self-contained algorithm for the attitude determination using magnetometers and accelerometers, for application on a satellite simulator based on frictionless air bearing tables. However, it is known that magnetometers and accelerometers need to be calibrated so as to allow that measurements are used to their ultimate accuracy. A calibration method is implemented which proves to be essential for improving attitude determination accuracy. For the stepwise real-time attitude determination, it was used the well-known QUEST algorithm which yields quick response with reduced computer resources. The algorithms are tested and qualified with actual data collected on the streets under controlled situations. For such street runaways, the experiment employs a solid-state magnetoresistive magnetometer and an IMU navigation block consisting of triads of accelerometers and gyros, with MEMS technology. A GPS receiver is used to record positional information. The collected measurements are processed through the developed algorithms, and comparisons are made for attitude determination using calibrated and noncalibrated data. The results show that the attitude accuracy reaches the requirements for real-time operation for satellite simulator platforms.

  13. Kinematics of Gait: New Method for Angle Estimation Based on Accelerometers

    Directory of Open Access Journals (Sweden)

    Dejan B. Popović

    2011-11-01

    Full Text Available A new method for estimation of angles of leg segments and joints, which uses accelerometer arrays attached to body segments, is described. An array consists of two accelerometers mounted on a rigid rod. The absolute angle of each body segment was determined by band pass filtering of the differences between signals from parallel axes from two accelerometers mounted on the same rod. Joint angles were evaluated by subtracting absolute angles of the neighboring segments. This method eliminates the need for double integration as well as the drift typical for double integration. The efficiency of the algorithm is illustrated by experimental results involving healthy subjects who walked on a treadmill at various speeds, ranging between 0.15 m/s and 2.0 m/s. The validation was performed by comparing the estimated joint angles with the joint angles measured with flexible goniometers. The discrepancies were assessed by the differences between the two sets of data (obtained to be below 6 degrees and by the Pearson correlation coefficient (greater than 0.97 for the knee angle and greater than 0.85 for the ankle angle.

  14. Automatic Stress Detection in Working Environments From Smartphones' Accelerometer Data: A First Step.

    Science.gov (United States)

    Garcia-Ceja, Enrique; Osmani, Venet; Mayora, Oscar

    2016-07-01

    Increase in workload across many organizations and consequent increase in occupational stress are negatively affecting the health of the workforce. Measuring stress and other human psychological dynamics is difficult due to subjective nature of selfreporting and variability between and within individuals. With the advent of smartphones, it is now possible to monitor diverse aspects of human behavior, including objectively measured behavior related to psychological state and consequently stress. We have used data from the smartphone's built-in accelerometer to detect behavior that correlates with subjects stress levels. Accelerometer sensor was chosen because it raises fewer privacy concerns (e.g., in comparison to location, video, or audio recording), and because its low-power consumption makes it suitable to be embedded in smaller wearable devices, such as fitness trackers. About 30 subjects from two different organizations were provided with smartphones. The study lasted for eight weeks and was conducted in real working environments, with no constraints whatsoever placed upon smartphone usage. The subjects reported their perceived stress levels three times during their working hours. Using combination of statistical models to classify selfreported stress levels, we achieved a maximum overall accuracy of 71% for user-specific models and an accuracy of 60% for the use of similar-users models, relying solely on data from a single accelerometer. PMID:26087509

  15. Evaluation of a Hopkinson bar fly-away technique for high amplitude shock accelerometer calibration

    Energy Technology Data Exchange (ETDEWEB)

    Togami, T.C.; Bateman, V.I.; Brown, F.A.

    1997-11-01

    A split Hopkinson bar technique has been developed to evaluate the performance of accelerometers that measure large amplitude pulses. An evaluation of this technique has been conducted in the Mechanical Shock Laboratory at Sandia National Laboratories (SNL) to determine its use in the practical calibration of accelerometers. This evaluation consisted of three tasks. First, the quartz crystal was evaluated in a split Hopkinson bar configuration to evaluate the quartz gage`s sensitivity and frequency response at force levels of 18,000, 35,000 and 53,000 N at ambient temperature, {minus}48 C and +74 C. Secondly, the fly away technique was evaluated at shock amplitudes of 50,000, 100,000, 150,000 and 200,000 G (1 G = 9.81 m/s{sup 2}) at ambient temperature, {minus}48 C and +74 C. Lastly, the technique was performed using a NIST calibrated reference accelerometer. Comparisons of accelerations calculated from the quartz gage data and the measured acceleration data have shown very good agreement. Based on this evaluation, the authors expect this split Hopkinson fly away technique to be certified by the SNL Primary Standards Laboratory.

  16. Application of MEMS Accelerometers and Gyroscopes in Fast Steering Mirror Control Systems.

    Science.gov (United States)

    Tian, Jing; Yang, Wenshu; Peng, Zhenming; Tang, Tao; Li, Zhijun

    2016-01-01

    In a charge-coupled device (CCD)-based fast steering mirror (FSM) tracking control system, high control bandwidth is the most effective way to enhance the closed-loop performance. However, the control system usually suffers a great deal from mechanical resonances and time delays induced by the low sampling rate of CCDs. To meet the requirements of high precision and load restriction, fiber-optic gyroscopes (FOGs) are usually used in traditional FSM tracking control systems. In recent years, the MEMS accelerometer and gyroscope are becoming smaller and lighter and their performance have improved gradually, so that they can be used in a fast steering mirror (FSM) to realize the stabilization of the line-of-sight (LOS) of the control system. Therefore, a tentative approach to implement a CCD-based FSM tracking control system, which uses MEMS accelerometers and gyroscopes as feedback components and contains an acceleration loop, a velocity loop and a position loop, is proposed. The disturbance suppression of the proposed method is the product of the error attenuation of the acceleration loop, the velocity loop and the position loop. Extensive experimental results show that the MEMS accelerometers and gyroscopes can act the similar role as the FOG with lower cost for stabilizing the LOS of the FSM tracking control system. PMID:27023557

  17. Implementation of an iPhone wireless accelerometer application for the quantification of reflex response.

    Science.gov (United States)

    LeMoyne, Robert; Mastroianni, Timothy; Grundfest, Warren; Nishikawa, Kiisa

    2013-01-01

    The patellar tendon reflex represents an inherent aspect of the standard neurological evaluation. The features of the reflex response provide initial perspective regarding the status of the nervous system. An iPhone wireless accelerometer application integrated with a potential energy impact pendulum attached to a reflex hammer has been successfully developed, tested, and evaluated for quantifying the patellar tendon reflex. The iPhone functions as a wireless accelerometer platform. The wide coverage range of the iPhone enables the quantification of reflex response samples in rural and remote settings. The iPhone has the capacity to transmit the reflex response acceleration waveform by wireless transmission through email. Automated post-processing of the acceleration waveform provides feature extraction of the maximum acceleration of the reflex response ascertained after evoking the patellar tendon reflex. The iPhone wireless accelerometer application demonstrated the utility of the smartphone as a biomedical device, while providing accurate and consistent quantification of the reflex response.

  18. Classification accuracy of a single tri-axial accelerometer for training background and experience level in runners.

    Science.gov (United States)

    Kobsar, Dylan; Osis, Sean T; Hettinga, Blayne A; Ferber, Reed

    2014-07-18

    Accelerometers are increasingly used tools for gait analysis, but there remains a lack of research on their application to running and their ability to classify running patterns. The purpose of this study was to conduct an exploratory examination into the capability of a tri-axial accelerometer to classify runners of different training backgrounds and experience levels, according to their 3-dimensional (3D) accelerometer data patterns. Training background was examined with 14 competitive soccer players and 12 experienced marathon runners, and experience level was examined with 16 first-time and the same 12 experienced marathon runners. Discrete variables were extracted from 3D accelerations during a short run using root mean square, wavelet transformation, and autocorrelation procedures. A principal component analysis (PCA) was conducted on all variables, including gait speed to account for covariance. Eight PCs were retained, explaining 88% of the variance in the data. A stepwise discriminant analysis of PCs was used to determine the binary classification accuracy for training background and experience level, with and without the PC of Speed. With Speed, the accelerometer correctly classified 96% of runners for both training background and experience level. Without Speed, the accelerometer correctly classified 85% of runners based on training background, but only 68% based on experience level. These findings suggest that the accelerometer is effective in classifying athletes of different training backgrounds, but is less effective for classifying runners of different experience levels where gait speed is the primary discriminator. PMID:24837221

  19. The Development of a Dual-Warhead Impact System for Dynamic Linearity Measurement of a High-g Micro-Electro-Mechanical-Systems (MEMS) Accelerometer.

    Science.gov (United States)

    Shi, Yunbo; Yang, Zhicai; Ma, Zongmin; Cao, Huiliang; Kou, Zhiwei; Zhi, Dan; Chen, Yanxiang; Feng, Hengzhen; Liu, Jun

    2016-01-01

    Despite its extreme significance, dynamic linearity measurement for high-g accelerometers has not been discussed experimentally in previous research. In this study, we developed a novel method using a dual-warhead Hopkinson bar to measure the dynamic linearity of a high-g acceleration sensor with a laser interference impact experiment. First, we theoretically determined that dynamic linearity is a performance indicator that can be used to assess the quality merits of high-g accelerometers and is the basis of the frequency response. We also found that the dynamic linearity of the dual-warhead Hopkinson bar without an accelerometer is 2.5% experimentally. Further, we verify that dynamic linearity of the accelerometer is 3.88% after calibrating the Hopkinson bar with the accelerometer. The results confirm the reliability and feasibility of measuring dynamic linearity for high-g accelerometers using this method. PMID:27338383

  20. Preliminary research of magnetic levitation accelerometer%磁悬浮式加速度计前期研究

    Institute of Scientific and Technical Information of China (English)

    练斌; 叶凌云; 黄添添

    2012-01-01

    为设计新型的小型高精度磁悬浮式加速度计,利用仿真软件对自制超顺磁性加速度计悬浮体在外磁场中所受的磁力进行仿真,并通过悬浮实验测试超顺磁性加速度计悬浮体在常温常压下的悬浮性能.仿真结果表明:超顺磁性加速度计悬浮体在外磁场中所受的磁力完全受外磁场控制.悬浮实验表明:当外磁场强度合适时,超顺磁性加速度计悬浮体可在常温常压下实现悬浮.实验表明:新型超顺磁性加速度计悬浮体适用于设计小型高精度磁悬浮式加速度计.%To design new type of small size high precision magnetic levitation accelerometer, the magnetic force of self-made superparamagnetic levitalion object of accelerometer in external magnetic field is simulated by software, and the levitation properties of superparamagnetic levitation object by accelerometer is test by levitation experiments. Simulation results demonstrate that the superparamagnetic leritation object of accelerometer is fully controlled by external magnetic field. Levitation experiments indicate that the superparamagnetic levitation object of accelerometer can be levitated under normal temperature and pressure. Experimental results show that this superparamagnetic levitation object of accelerometer is suitable for designing small size high precision magnetic levitation accelerometer.

  1. Transmissive grating-reflective mirror-based fiber optic accelerometer for stable signal acquisition in industrial applications

    Science.gov (United States)

    Lee, Yeon-Gwan; Kim, Dae-Hyun; Kim, Chun-Gon

    2012-05-01

    This paper discusses an applicable fiber-optic accelerometer composed of a transmissive grating panel, a reflection mirror, and two optical fibers with a separation of quarter grating pitch as transceivers that monitor the low-frequency accelerations of civil engineering structures. This sensor structure brings together the advantages of both a simple sensor structure, which leads to simplified cable design by 50% in comparison with the conventional transmission-type fiber optic accelerometer, and a stable reflected signals acquisition with repeatability in comparison to the researched grating-reflection type fiber optic accelerometer. The vibrating displacement and sinusoidal acceleration measured from the proposed fiber optic sensor demonstrated good agreement with those of a commercial laser displacement sensor and a MEMS accelerometer without electromagnetic interference. The developed fiber optic accelerometer can be used in frequency ranges below 4.0 Hz with a margin of error that is less than 5% and a high sensitivity of 5.06 rad/(m/s)2.

  2. Development of wafer-level-packaging technology for simultaneous sealing of accelerometer and gyroscope under different pressures

    Science.gov (United States)

    Aono, T.; Suzuki, K.; Kanamaru, M.; Okada, R.; Maeda, D.; Hayashi, M.; Isono, Y.

    2016-10-01

    This research demonstrates a newly developed anodic bonding-based wafer-level-packaging technique to simultaneously seal an accelerometer in the atmosphere and a gyroscope in a vacuum with a glass cap for micro-electromechanical systems sensors. It is necessary for the accelerometer, with a damping oscillator, to be sealed in the atmosphere to achieve a high-speed response. As the gyroscope can achieve high sensitivity with a large displacement at the resonant frequency without air-damping, the gyroscope must be sealed in a vacuum. The technique consists of three processing steps: the first bonding step in the atmosphere for the accelerometer, the pressure control step and the second bonding step in a vacuum for the gyroscope. The process conditions were experimentally determined to achieve higher shear strength at the interface of the packaging. The packaging performance of the accelerometer and gyroscope after wafer-level packaging was also investigated using a laser Doppler velocimeter at room temperature. The amplitude at the resonant frequency of the accelerometer was reduced by air damping, and the quality factor of the gyroscope showed a value higher than 1000. The reliability of the gyroscope was also confirmed by a thermal cyclic test and an endurance test at high humidity and high temperature.

  3. Does a waist-worn ActiGraph accelerometer quantify community ambulation in persons with multiple sclerosis?

    Directory of Open Access Journals (Sweden)

    Jacob J. Sosnoff, PhD

    2012-12-01

    Full Text Available Accelerometry has been recognized as a method of objectively measuring community ambulation in persons with multiple sclerosis (MS. However, the assumption that walking itself serves as a major contributor to the accelerometer signal has yet to be tested. This study examined the assumption that community-based walking is a primary contributor to accelerometer output in MS. Ambulatory persons (5 males/17 females; 13 without aid/9 with aid with MS wore a triaxial accelerometer (ActiGraph GT3X, Health One Technologies; Fort Walton Beach, Florida as well as an IDEEA system (MiniSun, Inc; Fresno, Florida over the course of a single day. Outcome measures for the accelerometer included movement counts/hour for the vertical, anterior-posterior, and mediolateral axes. Outcomes for the IDEEA system included percent time walking, sitting, and standing, as well as walking speed. Pearson product correlations (r were used to examine the associations between outcomes from the accelerometer and IDEEA system. Significant correlations were observed between percent walking time and movement counts/hour along the vertical (r = 0.84 and anterior-posterior (r = 0.69 axes. Significant correlations were further noted between movement counts/hour along the vertical axis and walking speed (r = 0.45 and self-report walking impairment (r = −0.50 and disability (r = −0.46. Such observations further support accelerometry as an objective marker of community ambulation in persons with MS.

  4. Monitoring recovery of gait balance control following concussion using an accelerometer.

    Science.gov (United States)

    Howell, David; Osternig, Louis; Chou, Li-Shan

    2015-09-18

    Despite medical best-practice recommendations, no consistent standard exists to systematically monitor recovery from concussion. Studies utilizing camera-based systems have reported center-of-mass (COM) motion control deficits persisting in individuals with concussion up to two months post-injury. The use of an accelerometer may provide an efficient and sensitive method to monitor COM alterations following concussion that can be employed in clinical settings. This study examined: (1) frontal/sagittal plane acceleration characteristics during dual-task walking for individuals with concussion and healthy controls; and (2) the effectiveness of utilizing acceleration characteristics to classify concussed and healthy individuals via receiver operating characteristic (ROC) curve analyses. Individuals with concussion completed testing within 72 h as well as 1 week, 2 weeks, 1 month, and 2 months post-injury. Control subjects completed the same protocol in similar time increments. Participants walked and simultaneously completed a cognitive task while wearing an accelerometer attached to L5. Participants with concussion walked with significantly less peak medial-lateral acceleration during 55-75% gait cycle (p=0.04) throughout the testing period compared with controls. Moderate levels of sensitivity and specificity were found at the 72 h and 1 week testing times (sensitivity=0.70, specificity=0.71). ROC analysis revealed significant AUC values at the 72 h (AUC=0.889) and two week (AUC=0.810) time points. Accelerometer-derived measurements may assist in detecting frontal plane control deficits during dual-task walking post-concussion, consistent with camera-based studies. These initial findings demonstrate potential for using accelerometry as a tool for clinicians to monitor gait balance control following concussion. PMID:26152463

  5. Metabolic responses of upper-body accelerometer-controlled video games in adults.

    Science.gov (United States)

    Stroud, Leah C; Amonette, William E; Dupler, Terry L

    2010-10-01

    Historically, video games required little physical exertion, but new systems utilize handheld accelerometers that require upper-body movement. It is not fully understood if the metabolic workload while playing these games is sufficient to replace routine physical activity. The purpose of this study was to quantify metabolic workloads and estimate caloric expenditure while playing upper-body accelerometer-controlled and classic seated video games. Nineteen adults completed a peak oxygen consumption treadmill test followed by an experimental session where exercising metabolism and ventilation were measured while playing 3 video games: control (CON), low activity (LOW) and high activity (HI). Resting metabolic measures (REST) were also acquired. Caloric expenditure was estimated using the Weir equation. Mean oxygen consumption normalized to body weight for HI condition was greater than LOW, CON, and REST. Mean oxygen consumption normalized to body weight for LOW condition was also greater than CON and REST. Mean exercise intensities of oxygen consumption reserve for HI, LOW, and CON were 25.8% ± 5.1%, 6.4% ± 4.8%, and 0.8% ± 2.4%, respectively. Estimated caloric expenditure during the HI was significantly related to aerobic fitness, but not during other conditions. An active video game significantly elevated oxygen consumption and heart rate, but the increase was dependent on the type of game. The mean oxygen consumption reserve during the HI video game was below recommended international standards for moderate and vigorous activity. Although upper-body accelerometer-controlled video games provided a greater exercising stimulus than classic seated video games, these data suggest they should not replace routine moderate or vigorous exercise.

  6. The impact of accelerometer use in exercise-associated hypoglycemia prevention in type 1 diabetes.

    Science.gov (United States)

    Stenerson, Matthew; Cameron, Fraser; Payne, Shelby R; Payne, Sydney L; Ly, Trang T; Wilson, Darrell M; Buckingham, Bruce A

    2015-01-01

    Exercise-associated hypoglycemia is a common adverse event in people with type 1 diabetes. Previous in silico testing by our group demonstrated superior exercise-associated hypoglycemia mitigation when a predictive low glucose suspend (PLGS) algorithm was augmented to incorporate activity data. The current study investigates the effectiveness of an accelerometer-augmented PLGS algorithm in an outpatient exercise protocol. Subjects with type 1 diabetes on insulin pump therapy participated in two structured soccer sessions, one utilizing the algorithm and the other using the subject's regular basal insulin rate. Each subject wore their own insulin pump and a Dexcom G4™ Platinum continuous glucose monitor (CGM); subjects on-algorithm also wore a Zephyr BioHarness™ 3 accelerometer. The algorithm utilized a Kalman filter with a 30-minute prediction horizon. Activity and CGM readings were manually entered into a spreadsheet and at five-minute intervals, the algorithm indicated whether the basal insulin infusion should be on or suspended; any changes were then implemented by study staff. The rate of hypoglycemia during and after exercise (until the following morning) was compared between groups. Eighteen subjects (mean age 13.4 ± 3.7 years) participated in two separate sessions 7-22 days apart. The difference in meter blood glucose levels between groups at each rest period did not achieve statistical significance at any time point. Hypoglycemia during the session was recorded in three on-algorithm subjects, compared to six off-algorithm subjects. In the postexercise monitoring period, hypoglycemia occurred in two subjects who were on-algorithm during the session and four subjects who were off-algorithm. The accelerometer-augmented algorithm failed to prevent exercise-associated hypoglycemia compared to subjects on their usual basal rates. A larger sample size may have achieved statistical significance. Further research involving an automated system, a larger sample

  7. Traveling Atmospheric Disturbances (TADs) in the thermosphere inferred from accelerometer data at three altitudes

    Science.gov (United States)

    Bruinsma, Sean; Forbes, Jeffrey

    2010-05-01

    Densities derived from accelerometer measurements on the GRACE, CHAMP and Air Force/SETA satellites near 490, 390, and 220 km, respectively, are used to elucidate global-scale characteristics of traveling atmospheric disturbances. The accelerometers on the CHAMP and GRACE satellites have made it possible to accumulate near-continuous records of thermosphere density between about 320 and 490 km since May 2001, and July 2002, respectively. They have recorded the response to virtually every significant geomagnetic storm during this period. CHAMP and GRACE are in (near) polar and quasi-circular orbits, sampling 24 hr local time approximately every 4 and 5 months, respectively. These capabilities offer unique opportunities to study the temporal and latitudinal responses of the thermosphere to geomagnetic disturbances. The Air Force/SETA accelerometer data have also been processed, but the analysis is more complicated due to data gaps. Significant and unambiguous TAD activity in the observed response of the thermosphere was detected for about 25 events with CHAMP and GRACE, and less than 10 with SETA. The atmospheric variability is evaluated by de-trending the data, allowing the extraction of specific ranges in horizontal scale, and analyzing density "residuals". The scale of the perturbation is decisive for its lifetime and relative amplitude. Sometimes the disturbances represent wave-like structures propagating far from the source, and these so-called ‘TADs' were detected and described for the May 2003 storm for the first time. Some TADs traveled over the pole into the opposite hemisphere; this was found in both CHAMP and GRACE data. Most TADs propagate equatorward, but poleward propagating TADs have on occasion been detected too. The estimated speeds and amplitudes of the observed TADs, and their dependence on altitude and solar and geomagnetic activity in particular, will be presented in this poster.

  8. The Evaluation of Physical Stillness with Wearable Chest and Arm Accelerometer during Chan Ding Practice

    Directory of Open Access Journals (Sweden)

    Kang-Ming Chang

    2016-07-01

    Full Text Available Chan Ding training is beneficial to health and emotional wellbeing. More and more people have taken up this practice over the past few years. A major training method of Chan Ding is to focus on the ten Mailuns, i.e., energy points, and to maintain physical stillness. In this article, wireless wearable accelerometers were used to detect physical stillness, and the created physical stillness index (PSI was also shown. Ninety college students participated in this study. Primarily, accelerometers used on the arms and chest were examined. The results showed that the PSI values on the arms were higher than that of the chest, when participants moved their bodies in three different ways, left-right, anterior-posterior, and hand, movements with natural breathing. Then, they were divided into three groups to practice Chan Ding for approximately thirty minutes. Participants without any Chan Ding experience were in Group I. Participants with one year of Chan Ding experience were in Group II, and participants with over three year of experience were in Group III. The Chinese Happiness Inventory (CHI was also conducted. Results showed that the PSI of the three groups measured during 20–30 min were 0.123 ± 0.155, 0.012 ± 0.013, and 0.001 ± 0.0003, respectively (p < 0.001 ***. The averaged CHI scores of the three groups were 10.13, 17.17, and 25.53, respectively (p < 0.001 ***. Correlation coefficients between PSI and CHI of the three groups were −0.440, −0.369, and −0.537, respectively (p < 0.01 **. PSI value and the wearable accelerometer that are presently available on the market could be used to evaluate the quality of the physical stillness of the participants during Chan Ding practice.

  9. The Evaluation of Physical Stillness with Wearable Chest and Arm Accelerometer during Chan Ding Practice.

    Science.gov (United States)

    Chang, Kang-Ming; Chun, Yu-Teng; Chen, Sih-Huei; Lu, Luo; Su, Hsiao-Ting Jannis; Liang, Hung-Meng; Santhosh, Jayasree; Ching, Congo Tak-Shing; Liu, Shing-Hong

    2016-01-01

    Chan Ding training is beneficial to health and emotional wellbeing. More and more people have taken up this practice over the past few years. A major training method of Chan Ding is to focus on the ten Mailuns, i.e., energy points, and to maintain physical stillness. In this article, wireless wearable accelerometers were used to detect physical stillness, and the created physical stillness index (PSI) was also shown. Ninety college students participated in this study. Primarily, accelerometers used on the arms and chest were examined. The results showed that the PSI values on the arms were higher than that of the chest, when participants moved their bodies in three different ways, left-right, anterior-posterior, and hand, movements with natural breathing. Then, they were divided into three groups to practice Chan Ding for approximately thirty minutes. Participants without any Chan Ding experience were in Group I. Participants with one year of Chan Ding experience were in Group II, and participants with over three year of experience were in Group III. The Chinese Happiness Inventory (CHI) was also conducted. Results showed that the PSI of the three groups measured during 20-30 min were 0.123 ± 0.155, 0.012 ± 0.013, and 0.001 ± 0.0003, respectively (p < 0.001 ***). The averaged CHI scores of the three groups were 10.13, 17.17, and 25.53, respectively (p < 0.001 ***). Correlation coefficients between PSI and CHI of the three groups were -0.440, -0.369, and -0.537, respectively (p < 0.01 **). PSI value and the wearable accelerometer that are presently available on the market could be used to evaluate the quality of the physical stillness of the participants during Chan Ding practice. PMID:27447641

  10. Vibration transmissibility on rifle shooter: A comparison between accelerometer and laser Doppler vibrometer data

    Science.gov (United States)

    Scalise, L.; Casacanditella, L.; Santolini, C.; Martarelli, M.; Tomasini, E. P.

    2014-05-01

    The transmission of mechanical vibrations from tools to human subjects is known to be potentially dangerous for the circulatory and neurological systems. It is also known that such damages are strictly depending on the intensity and the frequency range of the vibrational signals transferred to the different anatomical districts. In this paper, very high impulsive signals, generated during a shooting by a rifle, will be studied, being such signals characterised by a very high acceleration amplitude as well as high frequency range. In this paper, it will be presented an experimental setup aimed to collect experimental data relative to the transmission of the vibration signals from the rifle to the shoulder of subject during the shooting action. In particular the transmissibility of acceleration signals, as well as of the velocity signals, between the rifle stock and the subject's back shoulder will be measured using two piezoelectric accelerometers and a single point laser Doppler vibrometer (LDV). Tests have been carried out in a shooting lab where a professional shooter has conducted the experiments, using different experimental configurations: two different types of stocks and two kinds of bullets with different weights were considered. Two uniaxial accelerometers were fixed on the stock of the weapon and on the back of the shoulder of the shooter respectively. Vibration from the back shoulder was also measured by means of a LDV simultaneously. A comparison of the measured results will be presented and the pros and cons of the use of contact and non-contact transducers will be discussed taking into account the possible sources of the measurement uncertainty as unwanted sensor vibrations for the accelerometer.

  11. Changes in Physical Activity over Time in Young Children: A Longitudinal Study Using Accelerometers

    OpenAIRE

    Taylor, Rachael W; Williams, Sheila M.; Victoria L Farmer; Taylor, Barry J.

    2013-01-01

    Previous research has suggested that marked declines in physical activity occur during the preschool years, and across the transition into school. However, longitudinal studies using objective measures of activity have been limited by sample size and length of follow-up. The aims of this study were to determine how overall activity and time in different intensities of activity change in children followed from 3 to 7 years. Children (n = 242) wore Actical accelerometers at 3, 4, 5, 5.5, 6.5 an...

  12. Testing gravity beyond the standard model: status of GAP, an electrostatic accelerometer for interplanetary fundamental physics

    Science.gov (United States)

    Berge, Joel; Christophe, Bruno; Liorzou, Françoise

    Theories beyond the standard model aim to face several challenges: connect gravitation with the other three known forces, and shed light on dark matter and dark energy. Although General Relativity has been incredibly successful at passing laboratory / Solar System scales tests to date, it is a classical theory (hence, incompatible with quantum physics scales) and it fails at explaining large scale astrophysical observations such as galaxy rotation curves and the accelerated expansion of the Universe without introducing dark matter and dark energy. Thus, most theories beyond the standard model explore modifications to General Relativity. Those modifications, whether they consist in adding an extra scalar field or adding a scale-dependence to the gravitation laws, allow us to predict small deviations from General Relativity at laboratory / Solar System scales. For instance, such a deviation could have explained the Pioneer anomaly, where the Pioneer probes were measured to undergo an unexpected acceleration. Although this anomaly has recently been accounted for by an instrumental thermal radiation, precise measurements of the non-gravitational forces applied to the probes would have helped decide whether the observed behavior was due to gravitational or non-gravitational physics. As a result, several missions have been proposed to embark an accelerometer on-board an interplanetary probe. Indeed, an accelerometer will measure the non-gravitational accelerations applied to the probe, thereby separating the potentially measured departures from a pure geodetic trajectory into their gravitational and non-gravitational components, and allowing us to easily constrain General Relativity in deep space. The Gravity Advanced Package (GAP) is an instrument developed for this purpose. It is composed of a 3-axes electrostatic accelerometer called MicroSTAR and a rotating platform called Bias Rejection System. It aims to provide an unbiased measurement of a spacecraft's non

  13. Optimization of an Accelerometer and Gyroscope-Based Fall Detection Algorithm

    OpenAIRE

    Huynh, Quoc T.; Nguyen, Uyen D; Irazabal, Lucia B.; Nazanin Ghassemian; Tran, Binh Q.

    2015-01-01

    Falling is a common and significant cause of injury in elderly adults (>65 yrs old), often leading to disability and death. In the USA, one in three of the elderly suffers from fall injuries annually. This study’s purpose is to develop, optimize, and assess the efficacy of a falls detection algorithm based upon a wireless, wearable sensor system (WSS) comprised of a 3-axis accelerometer and gyroscope. For this study, the WSS is placed at the chest center to collect real-time motion data of va...

  14. Analysis and Prevention for Oscillation Failure of Capacitive Micro-accelerometers

    Institute of Scientific and Technical Information of China (English)

    WAN Caixin; DONG Jingxin; HAN Fengtian

    2010-01-01

    As actuator of the force-rebalanced servo loop, the electrostatic force generator of the micro-accelerometer shows high nonlinearity while the interpole of the micro-electro-mechanical system(MEMS) sensor is far away from its balance position. The control system cannot rebalance itself with the limited bandwidth after an external long overload, because the characteristics of the force generator differ from normal case. Although for similar problems, solutions with cascading lead-lag blocks, with the anti-windup(AW) technology, or with the sliding-mode control, are widely reported, the problems such as performance loss or difficulty to synthesize a digital controller still remain. Based on existing researches, remedies are developed by analyzing the characteristic of the system not only near the balance position, but also corresponding to the whole moveable range of the interpole, and a new controller is proposed. The solution is compared with the common solutions of cascading lead-lag blocks method, AW methods, and sliding mode methods. Comparison results show that the proposed solution avoid performance loss, compared to cascading lead-lag blocks solution; the proposed solution is easily synthesized and implemented in the analog servo loop of the micro-accelerometer, compared to digital AW methods; at the same time, the proposed solution avoids suffering the chattering effect problem but just utilize it, compared to the sliding-mode control solution. Nevertheless, comparison results show the solution is lack of commonality, since the solution is only more suitable to micro electrostatic force-rebalance system. The SIMULINK models with and without the proposed solution, taking typical micro-accelerometer parameters, have been set up for simulation; corresponding experiments utilizing electrometric method are also conducted after the successful simulations. Simulation and experiment results verify that the micro-accelerometer will reliably return to normal operation

  15. Temperature compensated, humidity insensitive, high-Tg TOPAS FBGs for accelerometers and microphones

    DEFF Research Database (Denmark)

    Stefani, Alessio; Yuan, W.; Markos, C.;

    2012-01-01

    In this paper we present our latest work on Fiber Bragg Gratings (FBGs) in microstructured polymer optical fibers (mPOFs) and their application as strain sensing transducers in devices, such as accelerometers and microphones. We demonstrate how the cross-sensitivity of the FBG to temperature...... is eliminated by using dual-FBG technology and how mPOFs fabricated from different grades of TOPAS with glass transition temperatures around 135 degrees C potentially allow high-temperature humidity insensitive operation. The results bring the mPOF FBG closer to being a viable technology for commercial...

  16. Lameness detection via leg-mounted accelerometers on dairy cows on four commercial farms.

    Science.gov (United States)

    Thorup, V M; Munksgaard, L; Robert, P-E; Erhard, H W; Thomsen, P T; Friggens, N C

    2015-10-01

    Lameness in dairy herds is traditionally detected by visual inspection, which is time-consuming and subjective. Compared with healthy cows, lame cows often spend longer time lying down, walk less and change behaviour around feeding time. Accelerometers measuring cow leg activity may assist farmers in detecting lame cows. On four commercial farms, accelerometer data were derived from hind leg-mounted accelerometers on 348 Holstein cows, 53 of them during two lactations. The cows were milked twice daily and had no access to pasture. During a lactation, locomotion score (LS) was assessed on average 2.4 times (s.d. 1.3). Based on daily lying duration, standing duration, walking duration, total number of steps, step frequency, motion index (MI, i.e. total acceleration) for lying, standing and walking, eight accelerometer means and their corresponding coefficient of variation (CV) were calculated for each week immediately before an LS. A principal component analysis was performed to evaluate the relationship between the variables. The effects of LS and farm on the principal components (PC) and on the variables were analysed in a mixed model. The first four PC accounted for 27%, 18%, 12% and 10% of the total variation, respectively. PC1 corresponded to Activity variability due to heavy loading by five CV variables related to standing and walking. PC2 corresponded to Activity level due to heavy loading by MI walking, MI standing and walking duration. PC3 corresponded to Recumbency due to heavy loading by four variables related to lying. PC4 corresponded mainly to Stepping due to heavy loading by step frequency. Activity variability at LS4 was significantly higher than at the lower LS levels. Activity level was significantly higher at LS1 than at LS2, which was significantly higher than at LS4. Recumbency was unaffected by LS. Stepping at LS1 and LS2 was significantly higher than at LS3 and LS4. Activity level was significantly lower on farm 3 compared with farms 1 and 2

  17. Interpreting sign components from accelerometer and sEMG data for automatic sign language recognition.

    Science.gov (United States)

    Li, Yun; Chen, Xiang; Zhang, Xu; Wang, Kongqiao; Yang, Jihai

    2011-01-01

    The identification of constituent components of each sign gesture is a practical way of establishing large-vocabulary sign language recognition (SLR) system. Aiming at developing such a system using portable accelerometer (ACC) and surface electromyographic (sEMG) sensors, this work proposes a method for automatic SLR at the component level. The preliminary experimental results demonstrate the effectiveness of the proposed method and the feasibility of interpreting sign components from ACC and sEMG data. Our study improves the performance of SLR based on ACC and sEMG sensors and will promote the realization of a large-vocabulary portable SLR system. PMID:22255059

  18. The Use of Accelerometers and Gyroscopes to Estimate Hip and Knee Angles on Gait Analysis

    Directory of Open Access Journals (Sweden)

    Francesco Alonge

    2014-05-01

    Full Text Available In this paper the performance of a sensor system, which has been developed to estimate hip and knee angles and the beginning of the gait phase, have been investigated. The sensor system consists of accelerometers and gyroscopes. A new algorithm was developed in order to avoid the error accumulation due to the gyroscopes drift and vibrations due to the ground contact at the beginning of the stance phase. The proposed algorithm have been tested and compared to some existing algorithms on over-ground walking trials with a commercial device for assisted gait. The results have shown the good accuracy of the angles estimation, also in high angle rate movement.

  19. Using hidden markov models to improve quantifying physical activity in accelerometer data - a simulation study.

    Directory of Open Access Journals (Sweden)

    Vitali Witowski

    Full Text Available INTRODUCTION: The use of accelerometers to objectively measure physical activity (PA has become the most preferred method of choice in recent years. Traditionally, cutpoints are used to assign impulse counts recorded by the devices to sedentary and activity ranges. Here, hidden Markov models (HMM are used to improve the cutpoint method to achieve a more accurate identification of the sequence of modes of PA. METHODS: 1,000 days of labeled accelerometer data have been simulated. For the simulated data the actual sedentary behavior and activity range of each count is known. The cutpoint method is compared with HMMs based on the Poisson distribution (HMM[Pois], the generalized Poisson distribution (HMM[GenPois] and the Gaussian distribution (HMM[Gauss] with regard to misclassification rate (MCR, bout detection, detection of the number of activities performed during the day and runtime. RESULTS: The cutpoint method had a misclassification rate (MCR of 11% followed by HMM[Pois] with 8%, HMM[GenPois] with 3% and HMM[Gauss] having the best MCR with less than 2%. HMM[Gauss] detected the correct number of bouts in 12.8% of the days, HMM[GenPois] in 16.1%, HMM[Pois] and the cutpoint method in none. HMM[GenPois] identified the correct number of activities in 61.3% of the days, whereas HMM[Gauss] only in 26.8%. HMM[Pois] did not identify the correct number at all and seemed to overestimate the number of activities. Runtime varied between 0.01 seconds (cutpoint, 2.0 minutes (HMM[Gauss] and 14.2 minutes (HMM[GenPois]. CONCLUSIONS: Using simulated data, HMM-based methods were superior in activity classification when compared to the traditional cutpoint method and seem to be appropriate to model accelerometer data. Of the HMM-based methods, HMM[Gauss] seemed to be the most appropriate choice to assess real-life accelerometer data.

  20. Design of a fibre-optic disc accelerometer: theory and experiment

    Science.gov (United States)

    Wang, Yongjie; Xiao, Hao; Zhang, Songwei; Li, Fang; Liu, Yuliang

    2007-06-01

    Mechanical principles of fibre-optic disc accelerometers (FODA) different from those assumed in previous calculation methods are presented. An FODA with a high sensitivity of 82 rad/g and a resonance frequency of 360 Hz is designed and tested. In this system, the minimum measurable demodulation phase of the phase-generated carrier (PGC) is 10-5 rad, and the minimum acceleration reaches 120 ng theoretically. This kind of FODA, with its high responsivity, all-optic-fibre configuration, small size, light weight and stiff shell housing, ensures effective performance in practice.

  1. Estimation of the respiratory ventilation rate of preschool children in daily life using accelerometers.

    Science.gov (United States)

    Kawahara, Junko; Tanaka, Shigeho; Tanaka, Chiaki; Hikihara, Yuki; Aoki, Yasunobu; Yonemoto, Junzo

    2011-01-01

    Inhalation rate is an essential factor for determining the inhaled dose of air pollutants. Here, accelerometers were used to develop regression equations for predicting the minute ventilation rate (V(E)) to estimate the daily inhalation rate in young children. Body acceleration and heart rate were measured in 29 Japanese preschool children (6 yr of age) during nine different levels of activities (lying down, sitting, standing, playing with plastic bricks, walking, building with blocks, climbing stairs, ball tossing, and running) using the Actical omnidirectional accelerometer, the ActivTracer triaxial accelerometer, and a heart rate monitor. Measurements were calibrated against the V(E) measured by the Douglas bag method. ActivTracer accelerometer measurements gave a strong correlation with V(E) (Pearson's r = 0.913), which was marginally stronger than that for the Actical counts (r = 0.886) and comparable to the correlation between heart rate and logarithmic V(E) (r = 0.909). According to the linear regression equation, the V(E) for lying down, sitting, standing, playing with plastic bricks, walking, and running was overestimated by 14-60% by the Actical and by 14-37% by the ActivTracer. By comparison, for building with blocks, climbing stairs, and ball tossing, the V(E) was underestimated by 19-23% by the Actical and by 13-18% by the ActivTracer. When these three activities were excluded, a stronger correlation was found between the V(E) and ActivTracer measurements (r = 0.949); this correlation was 0.761 for the three excluded activities. Discriminant analysis showed that the ratio between vertical and horizontal acceleration obtained by the ActivTracer could discriminate walking from building with blocks, climbing stairs, and ball tossing with a sensitivity of 75%. The error in estimating V(E) was considerably improved for the ActivTracer measurements by the use of two regression equations developed for each type of activity. PMID:21305887

  2. Tests Results of the Electrostatic Accelerometer Flight Models for Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Perrot, E.; Boulanger, D.; Christophe, B.; Foulon, B.; Lebat, V.; Huynh, P. A.; Liorzou, F.

    2015-12-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, which will produce an accurate model of the Earth's gravity field variation providing global climatic data during five years at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link measuring the inter-satellites distance variation. Earth's mass distribution non-uniformities cause variations of the inter-satellite distance. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics - SUM - and the Front-End Electronic Unit - FEEU) and the Interface Control Unit - ICU. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained at the center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the output measurement of the accelerometer. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with micro-gravity pendulum bench on ground and with drops in ZARM catapult. The Critical Design Review was achieved successfully on September 2014. The Engineering Model (EM) was integrated and tested successfully, with ground levitation, drops, Electromagnetic Compatibility and thermal vacuum. The integration of the two Flight Models was done on July 2015. The

  3. Status of Electrostatic Accelerometer Development for Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Perrot, Eddy; Boulanger, Damien; Christophe, Bruno; Foulon, Bernard; Liorzou, Françoise; Lebat, Vincent; Huynh, Phuong-Anh

    2015-04-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, which will produce an accurate model of the Earth's gravity field variation providing global climatic data during five years at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link measuring the inter-satellites distance variation. Earth's mass distribution non-uniformities cause variations of the inter-satellite distance. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics - SUM - and the Front-End Electronic Unit - FEEU) and the Interface Control Unit - ICU. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained at the center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with micro-gravity pendulum bench on ground and with drops in ZARM catapult. The Critical Design Review was achieved successfully on September 2014. The Engineering Model (EM) was integrated and tested successfully, with ground levitation, drops, Electromagnetic Compatibility and thermal vacuum. The integration of the first Flight Model has begun on December 2014

  4. Ngram time series model to predict activity type and energy cost from wrist, hip and ankle accelerometers: implications of age.

    Science.gov (United States)

    Strath, Scott J; Kate, Rohit J; Keenan, Kevin G; Welch, Whitney A; Swartz, Ann M

    2015-11-01

    To develop and test time series single site and multi-site placement models, we used wrist, hip and ankle processed accelerometer data to estimate energy cost and type of physical activity in adults. Ninety-nine subjects in three age groups (18-39, 40-64, 65 +  years) performed 11 activities while wearing three triaxial accelereometers: one each on the non-dominant wrist, hip, and ankle. During each activity net oxygen cost (METs) was assessed. The time series of accelerometer signals were represented in terms of uniformly discretized values called bins. Support Vector Machine was used for activity classification with bins and every pair of bins used as features. Bagged decision tree regression was used for net metabolic cost prediction. To evaluate model performance we employed the jackknife leave-one-out cross validation method. Single accelerometer and multi-accelerometer site model estimates across and within age group revealed similar accuracy, with a bias range of -0.03 to 0.01 METs, bias percent of -0.8 to 0.3%, and a rMSE range of 0.81-1.04 METs. Multi-site accelerometer location models improved activity type classification over single site location models from a low of 69.3% to a maximum of 92.8% accuracy. For each accelerometer site location model, or combined site location model, percent accuracy classification decreased as a function of age group, or when young age groups models were generalized to older age groups. Specific age group models on average performed better than when all age groups were combined. A time series computation show promising results for predicting energy cost and activity type. Differences in prediction across age group, a lack of generalizability across age groups, and that age group specific models perform better than when all ages are combined needs to be considered as analytic calibration procedures to detect energy cost and type are further developed. PMID:26449155

  5. ISA on the Moon: useful applications of accelerometers for planetary missions support

    Science.gov (United States)

    Peron, Roberto; Iafolla, Valerio; Fiorenza, Emiliano; Lefevre, Carlo; Milyukov, Vadim; Nozzoli, Sergio; Persichini, Marco; Reale, Andrea; Santoli, Francesco

    The last decade has seen a renewed interest for the exploration of our natural satellite, the Moon. This interest is expected to grow in the foreseeable future, also in view of new manned missions. The scientific reasons for lunar exploration are well-justified, in particular there is space for improved models of its gravitational field: these models will be useful in constraining its formation, evolution and present composition. All the main techniques to obtain information on the fine characteristics of the gravitational selenopotential imply the use of an orbiter in close Moon orbit. The data analysis requires complex models to take into account the dynamical environment the satellite moves in: their intrinsic limitations in describing the non-gravitational perturbations can be overcome measuring them directly by means of an on-board accelerometer like ISA (Italian Spring Accelerometer). Some estimates will be discussed in the context of the proposed mission MAGIA (Missione Altimetrica Gravimetrica Geochimica lunAre). The usefulness of this instrument goes beyond this basic application, and scenarios can be envisaged in which gradiometric and in-situ (seismological) measurements are performed. Each of these possible applications — extending to a wide range of conditions in Solar System exploration — will be shown and discussed.

  6. A novel sacrificial-layer process based on anodic bonding and its application in an accelerometer

    Directory of Open Access Journals (Sweden)

    Lingyun Wang

    2015-04-01

    Full Text Available It is found in our experiments that the depletion layer of anodic bonding is etched faster than the bulk glass (Pyrex 7740 in hydrofluoric acid (HF. Based on this interesting phenomenon, a novel process of a sacrificial layer is proposed in this paper. In order to deeply understand and investigate the rules concerning the influence of bonding parameters on this effect, firstly the width of the depletion layer under different bonding voltages and temperatures and the selection ratio of etching are revealed. To validate the feasibility of the method, a micro-machined accelerometer is designed and fabricated. The test results of resonant frequency and sensitivity of the fabricated accelerometer are 3254.5 Hz and 829.85–844.93 mV/g, respectively. This was further evidence that the depletion layer could be used as a sacrificial layer and the removable structure could be successfully released by fast etching this layer. The important feature of this method is that only one mask is needed in the whole process and therefore it could greatly simplify the fabrication process of the device.

  7. Accelerometer Load Profiles for Basketball-Specific Drills in Elite Players

    Directory of Open Access Journals (Sweden)

    Xavi Schelling, Lorena Torres

    2016-12-01

    Full Text Available The purpose of this study was to quantify the workload during basketball-specific drills measured through microtechnology. Twelve professional male basketball players from the Spanish 1st Division were monitored over a 4-week period. Data were collected from 16 sessions, for a total of 95 ± 33 drills per player. Workload data (Acceleration load; AL were obtained from a tri-axial accelerometer at 100Hz sampling frequency, and were expressed over time (AL.min-1. Comparisons among training drills (i.e., 2v2, 3v3, 4v4, and 5v5 were assessed via standardized mean differences. Full-court 3v3 and 5v5 showed the highest physical demand (AL.min-1: 18.7 ± 4.1 and 17.9 ± 4.6, respectively compared with other traditional balanced basketball drills such as 2v2 and 4v4 (14.6 ± 2.8 and 13.8±2.5, respectively. The AL.min-1 on half-court showed trivial-to-moderate differences with a likely increase of ~10-20% in 2v2 drill compared with any other formats. This study provides insight into the specific requirements of a range of exercises typically performed in basketball sessions. The use of accelerometer data is presented as a useful tool in assessing the workload.

  8. Fall-detection solution for mobile platforms using accelerometer and gyroscope data.

    Science.gov (United States)

    De Cillisy, Francesca; De Simioy, Francesca; Guidoy, Floriana; Incalzi, Raffaele Antonelli; Setolay, Roberto

    2015-08-01

    Falls are a major health risk that diminish the quality of life among elderly people. Apart from falls themselves, most dramatic consequences are usually related with long lying periods that can cause serious side effects. These findings call for pervasive long-term fall detection systems able to automatically detect falls. In this paper, we propose an effective fall detection algorithm for mobile platforms. Using data retrieved from wearable sensors, such as Inertial Measurements Units (IMUs) and/or SmartPhones (SPs), our algorithm is able to detect falls using features extracted from accelerometer and gyroscope. While mostly of the mobile-based solutions for fall management deal only with accelerometer data, in the proposed approach we combine the instantaneous acceleration magnitude vector with changes of the user's heading in a Threshold Based Algorithm (TBA). In such a way, we were able to handle falls detection with minimal computational load, increasing the overall system accuracy with respect to traditional fall management methods. Experimental results show the strong detection performance of the proposed solution in discriminating between falls and typical Activities of Daily Living (ADLs) presenting fall-like acceleration patterns. PMID:26737103

  9. High performance, accelerometer-based control of the Mini-MAST structure at Langley Research Center

    Science.gov (United States)

    Collins, Emmanuel G., Jr.; King, James A.; Phillips, Douglas J.; Hyland, David C.

    1991-01-01

    Many large space system concepts will require active vibration control to satisfy critical performance requirements such as line of sight pointing accuracy and constraints on rms surface roughness. In order for these concepts to become operational, it is imperative that the benefits of active vibration control be shown to be practical in ground based experiments. The results of an experiment shows the successful application of the Maximum Entropy/Optimal Projection control design methodology to active vibration control for a flexible structure. The testbed is the Mini-Mast structure at NASA-Langley and has features dynamically traceable to future space systems. To maximize traceability to real flight systems, the controllers were designed and implemented using sensors (four accelerometers and one rate gyro) that are actually mounted to the structure. Ground mounted displacement sensors that could greatly ease the control design task were available but were used only for performance evaluation. The use of the accelerometers increased the potential of destabilizing the system due to spillover effects and motivated the use of precompensation strategy to achieve sufficient compensator roll-off.

  10. Accuracy improvement in a calibration test bench for accelerometers by a vision system

    Science.gov (United States)

    D'Emilia, Giulio; Di Gasbarro, David; Gaspari, Antonella; Natale, Emanuela

    2016-06-01

    A procedure is described in this paper for the accuracy improvement of calibration of low-cost accelerometers in a prototype rotary test bench, driven by a brushless servo-motor and operating in a low frequency range of vibrations (0 to 5 Hz). Vibration measurements by a vision system based on a low frequency camera have been carried out, in order to reduce the uncertainty of the real acceleration evaluation at the installation point of the sensor to be calibrated. A preliminary test device has been realized and operated in order to evaluate the metrological performances of the vision system, showing a satisfactory behavior if the uncertainty measurement is taken into account. A combination of suitable settings of the control parameters of the motion control system and of the information gained by the vision system allowed to fit the information about the reference acceleration at the installation point to the needs of the procedure for static and dynamic calibration of three-axis accelerometers.

  11. Microgravity Level Measurement of the Beijing Drop Tower Using a Sensitive Accelerometer

    Science.gov (United States)

    Liu, T. Y.; Wu, Q. P.; Sun, B. Q.; Han, F. T.

    2016-08-01

    Drop tower is the most common ground-based facility to provide microgravity environment and widely used in many science experiments. A differential space accelerometer has been proposed to test the spin-gravity interaction between rotating extended bodies onboard a drag-free satellite. In order to assist design and test of this inertial sensor in a series of ground- based pre-flight experiments, it is very important to know accurately the residual acceleration of drop towers. In this report, a sensitive instrument for this purpose was built with a high-performance servo quartz accelerometer, and the dedicated interface electronics design providing small full-scale range and high sensitivity, up to 136.8 V/g0. The residual acceleration at the Beijing drop tower was measured using two different drop capsules. The experimental result shows that the microgravity level of the free-falling double capsule is better than 2 × 10‑4g0 (Earth’s gravity). The measured data in this report provides critical microgravity information for design of the following ground experiments.

  12. The Practical Design of In-vehicle Telematics Device with GPS and MEMS Accelerometers

    Directory of Open Access Journals (Sweden)

    D. M. Dramićanin

    2012-11-01

    Full Text Available The latest generation of vehicle tracking devices relies not only on Global Positioning System (GPS but also uses low-cost Micro-Electro-Mechanical Systems (MEMS accelerometers. This combination supports new services such as driving style characterization and Automatic Crash Notification (ACN. Our focus will be on practical considerations of such a telematics unit. The paper will consider the boundaries of allowed errors and minimal requirements for sensors and mounting requirements. Sensor range for crash detection and impact angle estimation was tested on field trials with two units containing accelerometers range of 18g and 2g. The kinematic orientation of vehicle is evaluated in a series of field trials with a resulting standard deviation of estimation of 1.67°. The second run of experiments considers the dynamic range and sampling rate of sensors during collision. A sensor range of 8g (typical for present-day telematics devices can be used to detect crash without accurate knowledge of impact angle.

  13. Microgravity Level Measurement of the Beijing Drop Tower Using a Sensitive Accelerometer.

    Science.gov (United States)

    Liu, T Y; Wu, Q P; Sun, B Q; Han, F T

    2016-01-01

    Drop tower is the most common ground-based facility to provide microgravity environment and widely used in many science experiments. A differential space accelerometer has been proposed to test the spin-gravity interaction between rotating extended bodies onboard a drag-free satellite. In order to assist design and test of this inertial sensor in a series of ground- based pre-flight experiments, it is very important to know accurately the residual acceleration of drop towers. In this report, a sensitive instrument for this purpose was built with a high-performance servo quartz accelerometer, and the dedicated interface electronics design providing small full-scale range and high sensitivity, up to 136.8 V/g0. The residual acceleration at the Beijing drop tower was measured using two different drop capsules. The experimental result shows that the microgravity level of the free-falling double capsule is better than 2 × 10(-4)g0 (Earth's gravity). The measured data in this report provides critical microgravity information for design of the following ground experiments. PMID:27530726

  14. Modeling the Microstructure Curvature of Boron-Doped Silicon in Bulk Micromachined Accelerometer

    Directory of Open Access Journals (Sweden)

    Xiaoping He

    2013-01-01

    Full Text Available Microstructure curvature, or buckling, is observed in the micromachining of silicon sensors because of the doping of impurities for realizing certain electrical and mechanical processes. This behavior can be a key source of error in inertial sensors. Therefore, identifying the factors that influence the buckling value is important in designing MEMS devices. In this study, the curvature in the proof mass of an accelerometer is modeled as a multilayered solid model. Modeling is performed according to the characteristics of the solid diffusion mechanism in the bulk-dissolved wafer process (BDWP based on the self-stopped etch technique. Moreover, the proposed multilayered solid model is established as an equivalent composite structure formed by a group of thin layers that are glued together. Each layer has a different Young’s modulus value and each undergoes different volume shrinkage strain owing to boron doping in silicon. Observations of five groups of proof mass blocks of accelerometers suggest that the theoretical model is effective in determining the buckling value of a fabricated structure.

  15. Spend Less, Get More? Using Low-Cost Accelerometers to Calculate Building Responses

    Science.gov (United States)

    Chung, A. I.; Lawrence, J. F.; Prieto, G.; Kohler, M. D.; Cochran, E. S.

    2009-12-01

    We present a new technique for predicting the earthquake responses of various structures, and we demonstrate its effectiveness by applying the method to several buildings, including several newly instrumented buildings around the Stanford University campus. While the use of ambient noise recordings to determine structural qualities of buildings is not new, our technique produces robust results that are independent of the noise sources. The process of averaging 10-minute inter-station transfer functions for a long duration (approximately 14 days) generates robust building responses comparable to those generated with earthquake data. The method allows us to employ large volumes of data recorded from low-gain accelerometers such as those currently used by the Quake-Catcher Network. Furthermore, as we can obtain the phase information, we can Fourier transform the transfer functions into the time domain to calculate the Impulse Response Function (IRF). The IRF can then be used to approximate a building’s response to a moderate earthquake. Using small, inexpensive accelerometers means that there is the exciting potential of being able to perform minimally invasive campaign-style state-of-health monitoring for many buildings at low cost. The increased data volume will provide useful and dependable results for many structures, thereby improving our understanding of building responses.

  16. Improving the response of accelerometers for automotive applications by using LMS adaptive filters.

    Science.gov (United States)

    Hernandez, Wilmar; de Vicente, Jesús; Sergiyenko, Oleg; Fernández, Eduardo

    2010-01-01

    In this paper, the least-mean-squares (LMS) algorithm was used to eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications. This kind of accelerometer is designed to be easily mounted in hard to reach places on vehicles under test, and they usually feature ranges from 50 to 2,000 g (where is the gravitational acceleration, 9.81 m/s(2)) and frequency responses to 3,000 Hz or higher, with DC response, durable cables, reliable performance and relatively low cost. However, here we show that the response of the sensor under test had a lot of noise and we carried out the signal processing stage by using both conventional and optimal adaptive filtering. Usually, designers have to build their specific analog and digital signal processing circuits, and this fact increases considerably the cost of the entire sensor system and the results are not always satisfactory, because the relevant signal is sometimes buried in a broad-band noise background where the unwanted information and the relevant signal sometimes share a very similar frequency band. Thus, in order to deal with this problem, here we used the LMS adaptive filtering algorithm and compare it with others based on the kind of filters that are typically used for automotive applications. The experimental results are satisfactory.

  17. Temperature compensation method for the resonant frequency of a differential vibrating accelerometer using electrostatic stiffness control

    Science.gov (United States)

    Lee, Jungshin; Rhim, Jaewook

    2012-09-01

    Differential vibrating accelerometer (DVA) is a resonant-type sensor which detects the change in the resonant frequency in the presence of acceleration input, i.e. inertial loading. However, the resonant frequency of micromachined silicon resonators is sensitive to the temperature change as well as the input acceleration. Therefore, to design a high-precision vibrating accelerometer, the temperature sensitivity of the resonant frequency has to be predicted and compensated accurately. In this study, a temperature compensation method for resonant frequency is proposed which controls the electrostatic stiffness of the dual-ended tuning fork (DETF) using the temperature-dependent dc voltage between the parallel plate electrodes. To do this, the electromechanical model is derived first to predict the change in the electrostatic stiffness and the resonant frequency resulting from the dc voltage between the resonator and the electrodes. Next, the temperature sensitivity of the resonant frequency is modeled, estimated and compared with the measured values. Then it is shown that the resonant frequency of the DETF can be kept constant in the operating temperature range by applying the temperature-dependent driving voltage to the parallel plate electrodes. The proposed method is validated through experiment.

  18. Microgravity Level Measurement of the Beijing Drop Tower Using a Sensitive Accelerometer

    Science.gov (United States)

    Liu, T. Y.; Wu, Q. P.; Sun, B. Q.; Han, F. T.

    2016-01-01

    Drop tower is the most common ground-based facility to provide microgravity environment and widely used in many science experiments. A differential space accelerometer has been proposed to test the spin-gravity interaction between rotating extended bodies onboard a drag-free satellite. In order to assist design and test of this inertial sensor in a series of ground- based pre-flight experiments, it is very important to know accurately the residual acceleration of drop towers. In this report, a sensitive instrument for this purpose was built with a high-performance servo quartz accelerometer, and the dedicated interface electronics design providing small full-scale range and high sensitivity, up to 136.8 V/g0. The residual acceleration at the Beijing drop tower was measured using two different drop capsules. The experimental result shows that the microgravity level of the free-falling double capsule is better than 2 × 10−4g0 (Earth’s gravity). The measured data in this report provides critical microgravity information for design of the following ground experiments. PMID:27530726

  19. Validation of Accelerometer Thresholds and Inclinometry for Measurement of Sedentary Behavior in Young Adult University Students.

    Science.gov (United States)

    Peterson, Neil E; Sirard, John R; Kulbok, Pamela A; DeBoer, Mark D; Erickson, Jeanne M

    2015-12-01

    Sedentary behavior (SB) is a major contributor to obesity and significant morbidity and mortality in adolescence and adulthood, yet measurement of SB is still evolving. The purpose of this study was to assess the degree of construct validity of the inclinometer function and single-axis and vector magnitude accelerometry metrics of the ActiGraph GT3X+ in objectively measuring SB and physical activity in 28 young adult university students who performed nine semi-structured activities, each for five minutes: lying, sitting, reading, seated video gaming, video watching, seated conversation, standing, stationary biking, and treadmill walking. Inclinometry and four output metrics from the ActiGraph were analyzed in comparison to direct observation by a researcher recorded each minute. For overall accuracy in measuring both SB and physical activity, all four accelerometer metrics (94.7-97.8%) outperformed the inclinometer function (70.9%). Vector magnitude accelerometry with a threshold of 150 counts per minute as the cut point for sedentary behavior was superior to other methods. While accelerometry was more accurate overall at detecting the behaviors tested, inclinometry had some advantages over accelerometry methods at detecting walking, biking, and standing. The findings support use of accelerometry as a valid objective measure of body movement, while use of inclinometry as a sole measure is not recommended. Additional research would be beneficial to improve the calibration of the inclinometer and explore ways of combining this with accelerometer data for objectively measuring SB and physical activity. PMID:26444969

  20. Seismic monitoring by piezoelectric accelerometers of a damaged historical monument in downtown L’Aquila

    Directory of Open Access Journals (Sweden)

    Giuseppe Di Giulio

    2015-03-01

    Full Text Available We show the preliminary seismic monitoring of a historical church in L’Aquila (central Italy, which was strongly damaged by the 2009 seismic sequence. This structure, S. Maria del Suffragio church, suffered the collapse of a great part of the dome during the April 6th 2009 Mw 6.1 earthquake. In this paper, recordings of ambient noise and local earthquakes have been analyzed. The seismic data were recorded by means of a dynamic monitoring system (19 mono-directional and 3 tri-directional piezoelectric accelerometers and of two velocimeters, with all the instruments installed into the church. The aim of this research is the evaluation of the performance of the accelerometers of the monitoring system in case of low-amplitude vibrations. Simple techniques of analysis commonly employed in the seismic characterization of buildings have been applied. The reliability of the in-situ data was evaluated and the main modal parameters (natural frequencies and damping ratio of the church were presented.

  1. Sensitivity Jump of Micro Accelerometer Induced by Micro-fabrication Defects of Micro Folded Beams

    Science.gov (United States)

    Zhou, Wu; Chen, Lili; Yu, Huijun; Peng, Bei; Chen, Yu

    2016-08-01

    The abnormal phenomenon occurring in sensor calibration is an obstacle to product development but a useful guideline to product improvement. The sensitivity jump of micro accelerometers in the calibrating process is recognized as an important abnormal behavior and investigated in this paper. The characteristics of jumping output in the centrifuge test are theoretically and experimentally analyzed and their underlying mechanism is found to be related to the varied stiffness of supporting beam induced by the convex defect on it. The convex defect is normally formed by the lithography deviation and/or etching error and can result in a jumping stiffness of folded microbeams and further influence the sensitivity when a part of the bending beams is stopped from moving by two surfaces contacting. The jumping level depends on the location of convex and has nothing to do with the contacting properties of beam and defects. Then the location of defect is predicted by theoretical model and simulation and verified by the observation of micro structures under microscopy. The results indicate that the tested micro accelerometer has its defect on the beam with a distance of about 290μm from the border of proof mass block.

  2. Fall-detection solution for mobile platforms using accelerometer and gyroscope data.

    Science.gov (United States)

    De Cillisy, Francesca; De Simioy, Francesca; Guidoy, Floriana; Incalzi, Raffaele Antonelli; Setolay, Roberto

    2015-08-01

    Falls are a major health risk that diminish the quality of life among elderly people. Apart from falls themselves, most dramatic consequences are usually related with long lying periods that can cause serious side effects. These findings call for pervasive long-term fall detection systems able to automatically detect falls. In this paper, we propose an effective fall detection algorithm for mobile platforms. Using data retrieved from wearable sensors, such as Inertial Measurements Units (IMUs) and/or SmartPhones (SPs), our algorithm is able to detect falls using features extracted from accelerometer and gyroscope. While mostly of the mobile-based solutions for fall management deal only with accelerometer data, in the proposed approach we combine the instantaneous acceleration magnitude vector with changes of the user's heading in a Threshold Based Algorithm (TBA). In such a way, we were able to handle falls detection with minimal computational load, increasing the overall system accuracy with respect to traditional fall management methods. Experimental results show the strong detection performance of the proposed solution in discriminating between falls and typical Activities of Daily Living (ADLs) presenting fall-like acceleration patterns.

  3. Measurement Uncertainty Analysis of an Accelerometer Calibration Using a POC Electromagnetic Launcher

    Energy Technology Data Exchange (ETDEWEB)

    Timpson, Erik J.; Engel, T. G.

    2012-06-12

    A pulse forming network (PFN), helical electromagnetic launcher (HEML), command module (CM), and calibration table (CT) were built and evaluated for the combined ability to calibrate an accelerometer. The PFN has a maximum stored nergy of 19.25 kJ bank and is fired by a silicon controlled rectifier (SCR), with appropriate safety precautions. The HEML is constructed out of G-10 fiberglass reinforced epoxy and is designed to accelerate a mass of 600 grams to a velocity of 10 meters per second. The CM is microcontroller-based running Arduino Software. The CM has a keypad input and 7 segment outputs of the PFN voltage and desired charging voltage. After entering a desired PFN voltage, the CM controls the charging of the PFN. When the two voltages are equal it sends a pulse to the SCR to fire the PFN and in turn, the HEML. The HEML projectile’s tip hits a target that is held by the CT. The CT consists of a table to hold the PFN and HEML, a vacuum chuck, air bearing, velocimeter and catch pot. The target is held with the vacuum chuck awaiting impact. After impact, the air bearing allows the target to fall freely so that the velocimeter can accurately read. A known acceleration is determined from the known change in velocity of the target. Thus, if an accelerometer was attached to the target, the measured value can be compared to the known value.

  4. Fiber-optical microphones and accelerometers based on polymer optical fiber Bragg gratings

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Stefani, Alessio; Bang, Ole;

    2010-01-01

    Polymer optical fibers (POFs) are ideal for applications as the sensing element in fiber-optical microphones and accelerometers based on fiber Bragg gratings (FBGs) due to their reduced Young’s Modulus of 3.2GPa, compared to 72GPa of Silica. To maximize the sensitivity and the dynamic range...... of the device the outer diameter and the length of the sensing fiber segment should be as small as possible. To this end we have fabricated 3mm FBGs in single-mode step-index POFs of diameter 115 micron, using 325nm UV writing and a phase-mask technique. 6mm POF sections with FBGs in the center have been glued...... to standard Silica SMF28 fibers. These POF FBGs have been characterized in terms of temperature and strain to find operating regimes with no hysteresis. Commercial fast wavelength interrogators (KHz) are shown to be able to track the thin POF FBGs and they are finally applied in a prototype accelerometer...

  5. Improving the response of accelerometers for automotive applications by using LMS adaptive filters.

    Science.gov (United States)

    Hernandez, Wilmar; de Vicente, Jesús; Sergiyenko, Oleg; Fernández, Eduardo

    2010-01-01

    In this paper, the least-mean-squares (LMS) algorithm was used to eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications. This kind of accelerometer is designed to be easily mounted in hard to reach places on vehicles under test, and they usually feature ranges from 50 to 2,000 g (where is the gravitational acceleration, 9.81 m/s(2)) and frequency responses to 3,000 Hz or higher, with DC response, durable cables, reliable performance and relatively low cost. However, here we show that the response of the sensor under test had a lot of noise and we carried out the signal processing stage by using both conventional and optimal adaptive filtering. Usually, designers have to build their specific analog and digital signal processing circuits, and this fact increases considerably the cost of the entire sensor system and the results are not always satisfactory, because the relevant signal is sometimes buried in a broad-band noise background where the unwanted information and the relevant signal sometimes share a very similar frequency band. Thus, in order to deal with this problem, here we used the LMS adaptive filtering algorithm and compare it with others based on the kind of filters that are typically used for automotive applications. The experimental results are satisfactory. PMID:22315542

  6. A novel accelerometer based on the first kind of ferrofluid levitation principle

    Science.gov (United States)

    Yao, Jie; Chen, Yibiao; Li, Zhenkun; Zhang, Tianqi; Li, Decai

    2016-09-01

    In this paper, a novel accelerometer exploiting the first kind of ferrofluid levitation principle is presented. The device consists of a piston-shaped container filled with ferrofluid surrounding a nonmagnetic insulating rod, which has the same shape as the container and is regarded as an inertial mass. Two annular magnets outside the container are used to create a non-uniform magnetic field which generates a powerful restoring force acting on the nonmagnetic rod. Under the influence of the external acceleration, two coils can detect the change of the volume distribution of the ferrofluid and transmit the voltage signal, which is proportional to the displacement of the nonmagnetic rod. The determination of the working range, linearity and sensitivity depends on the restoring force, thus these factors affecting the restoring force are sufficiently investigated by calculation and experiment. Furthermore, the comparison between numerical calculations and experimental measurements shows a good agreement. The static characteristics of the accelerometer are obtained by using an optimized structure.

  7. Application of Accelerometer Data in Precise Orbit Determination of GRACE -A and -B

    Institute of Scientific and Technical Information of China (English)

    Dong-Ju Peng; Bin Wu

    2008-01-01

    We investigate how well the GRACE satellite orbits can be determined using the onboard GPS data combined with the accelerometer data.The preprocessing of the accelerometer data and the methods and models used in the orbit determination are presented.In order to assess the orbit accuracy,a number of tests are made,including external orbit comparison,and through Satellite Laser Ranging (SLR) residuals and K-band ranging (KBR) residuals.It is shown that the standard deviations of the position differences between the so-called precise science orbits (PSO) produced by GFZ,and the single-difference (SD) and zero-difference (ZD) dynamic orbits are about 7 cm and 6 cm,respectively.The independent SLR validation indicates that the overall root-mean-squared (RMS) errors of the SD solution for days 309-329 of 2002 are about 4.93cm and 5.22cm,for GRACE-A and B respectively; theoverall RMS errors of the ZD solution are about 4.25 cm and 4.71 cm,respectively.The relative accuracy between the two GRACE satellites is validated by the KBR data to be on a level of 1.29 cm for the SD,and 1.03 cm for the ZD solution.

  8. Using commodity accelerometers and gyroscopes to improve speed and accuracy of JanusVF

    Science.gov (United States)

    Hutson, Malcolm; Reiners, Dirk

    2010-01-01

    Several critical limitations exist in the currently available commercial tracking technologies for fully-enclosed virtual reality (VR) systems. While several 6DOF solutions can be adapted to work in fully-enclosed spaces, they still include elements of hardware that can interfere with the user's visual experience. JanusVF introduced a tracking solution for fully-enclosed VR displays that achieves comparable performance to available commercial solutions but without artifacts that can obscure the user's view. JanusVF employs a small, high-resolution camera that is worn on the user's head, but faces backwards. The VR rendering software draws specific fiducial markers with known size and absolute position inside the VR scene behind the user but in view of the camera. These fiducials are tracked by ARToolkitPlus and integrated by a single-constraint-at-a-time (SCAAT) filter to update the head pose. In this paper we investigate the addition of low-cost accelerometers and gyroscopes such as those in Nintendo Wii remotes, the Wii Motion Plus, and the Sony Sixaxis controller to improve the precision and accuracy of JanusVF. Several enthusiast projects have implemented these units as basic trackers or for gesture recognition, but none so far have created true 6DOF trackers using only the accelerometers and gyroscopes. Our original experiments were repeated after adding the low-cost inertial sensors, showing considerable improvements and noise reduction.

  9. Temperature compensation method for the resonant frequency of a differential vibrating accelerometer using electrostatic stiffness control

    International Nuclear Information System (INIS)

    Differential vibrating accelerometer (DVA) is a resonant-type sensor which detects the change in the resonant frequency in the presence of acceleration input, i.e. inertial loading. However, the resonant frequency of micromachined silicon resonators is sensitive to the temperature change as well as the input acceleration. Therefore, to design a high-precision vibrating accelerometer, the temperature sensitivity of the resonant frequency has to be predicted and compensated accurately. In this study, a temperature compensation method for resonant frequency is proposed which controls the electrostatic stiffness of the dual-ended tuning fork (DETF) using the temperature-dependent dc voltage between the parallel plate electrodes. To do this, the electromechanical model is derived first to predict the change in the electrostatic stiffness and the resonant frequency resulting from the dc voltage between the resonator and the electrodes. Next, the temperature sensitivity of the resonant frequency is modeled, estimated and compared with the measured values. Then it is shown that the resonant frequency of the DETF can be kept constant in the operating temperature range by applying the temperature-dependent driving voltage to the parallel plate electrodes. The proposed method is validated through experiment. (paper)

  10. Sedentary Behavior in Preschoolers: How Many Days of Accelerometer Monitoring Is Needed?

    Directory of Open Access Journals (Sweden)

    Wonwoo Byun

    2015-10-01

    Full Text Available The reliability of accelerometry for measuring sedentary behavior in preschoolers has not been determined, thus we determined how many days of accelerometry monitoring are necessary to reliably estimate daily time spent in sedentary behavior in preschoolers. In total, 191 and 150 preschoolers (three to five years wore ActiGraph accelerometers (15-s epoch during the in-school (≥4 days and the total-day (≥6 days period respectively. Accelerometry data were summarized as time spent in sedentary behavior (min/h using three different cutpoints developed for preschool-age children (<37.5, <200, and <373 counts/15 s. The intraclass correlations (ICCs and Spearman-Brown prophecy formula were used to estimate the reliability of accelerometer for measuring sedentary behavior. Across different cutpoints, the ICCs ranged from 0.81 to 0.92 for in-school sedentary behavior, and from 0.75 to 0.81 for total-day sedentary behavior, respectively. To achieve an ICC of ≥0.8, two to four days or six to nine days of monitoring were needed for in-school sedentary behavior and total-day sedentary behavior, respectively. These findings provide important guidance for future research on sedentary behavior in preschool children using accelerometry. Understanding the reliability of accelerometry will facilitate the conduct of research designed to inform policies and practices aimed at reducing sedentary behavior in preschool children.

  11. Validity and Reliability of Gait and Postural Control Analysis Using the Tri-axial Accelerometer of the iPod Touch

    NARCIS (Netherlands)

    Kosse, Nienke M.; Caljouw, Simone; Vervoort, Danique; Vuillerme, Nicolas; Lamoth, Claudine J. C.

    2015-01-01

    Accelerometer-based assessments can identify elderly with an increased fall risk and monitor interventions. Smart devices, like the iPod Touch, with built-in accelerometers are promising for clinical gait and posture assessments due to easy use and cost-effectiveness. The aim of the present study wa

  12. Contributions of Italian Spring Accelerometer to lunar exploration: gravimetry and seismology .

    Science.gov (United States)

    Iafolla, V.; Fiorenza, E.; Lefevre, C.; Nozzoli, S.; Peron, R.; Reale, A.; Santoli, F.

    The opening of the XXI century sees a new wave in lunar exploration, with a significant number of missions, both ongoing and in preparation. The exploration of our natural satellite is indeed important to gain understanding on the formation of Solar System and to create the basis for a future human colonization. On this respect, the study of the Moon gravity field is an important tool: indeed, the fine knowledge of selenopotential will put strong constraints on Moon internal structure and composition, and therefore on its formation and evolution towards current state. This is one of the main objectives of the proposed mission MAGIA (Missione Altimetrica Gravimetrica geochImica lunAre). Its GRACE-like two-spacecraft configuration, with a microwave link between the main satellite and a subsatellite, will enable a uniform coverage with high resolution. Due to the selected very low orbit (necessary for high resolution), the contribution of non-gravitational perturbations to the spacecraft dynamics will not be negligible. An effective way of accounting for them in the orbit determination and parameter estimation procedure is to measure their effect directly by means of an on-board accelerometer like ISA (Italian Spring Accelerometer). Its role in the mission scenario is discussed. ISA instrument works also on ground, as seismometer and gravimeter, as it does in fact on Earth in a number of sites. It therefore can be used on lunar ground, as part of a selenodetic station permanently monitoring a selected location. This further capability of ISA accelerometer fits well with two current projects, the ILN (International Lunar Network) by NASA and the First Lunar Lander by ESA. Both aim to put on the Moon surface selenodetic stations which include instrumentation to investigate on its interior structure and composition, and on fundamental physics. Seismic measurements to constrain the Moon interior structure are a primary objective in both projects, and ISA is a candidate

  13. Design and Fabrication of a Differential Electrostatic Accelerometer for Space-Station Testing of the Equivalence Principle

    Directory of Open Access Journals (Sweden)

    Fengtian Han

    2016-08-01

    Full Text Available The differential electrostatic space accelerometer is an equivalence principle (EP experiment instrument proposed to operate onboard China’s space station in the 2020s. It is designed to compare the spin-spin interaction between two rotating extended bodies and the Earth to a precision of 10−12, which is five orders of magnitude better than terrestrial experiment results to date. To achieve the targeted test accuracy, the sensitive space accelerometer will use the very soft space environment provided by a quasi-drag-free floating capsule and long-time observation of the free-fall mass motion for integration of the measurements over 20 orbits. In this work, we describe the design and capability of the differential accelerometer to test weak space acceleration. Modeling and simulation results of the electrostatic suspension and electrostatic motor are presented based on attainable space microgravity condition. Noise evaluation shows that the electrostatic actuation and residual non-gravitational acceleration are two major noise sources. The evaluated differential acceleration noise is 1.01 × 10−9 m/s2/Hz1/2 at the NEP signal frequency of 0.182 mHz, by neglecting small acceleration disturbances. The preliminary work on development of the first instrument prototype is introduced for on-ground technological assessments. This development has already confirmed several crucial fabrication processes and measurement techniques and it will open the way to the construction of the final differential space accelerometer.

  14. Design and Fabrication of a Differential Electrostatic Accelerometer for Space-Station Testing of the Equivalence Principle.

    Science.gov (United States)

    Han, Fengtian; Liu, Tianyi; Li, Linlin; Wu, Qiuping

    2016-01-01

    The differential electrostatic space accelerometer is an equivalence principle (EP) experiment instrument proposed to operate onboard China's space station in the 2020s. It is designed to compare the spin-spin interaction between two rotating extended bodies and the Earth to a precision of 10(-12), which is five orders of magnitude better than terrestrial experiment results to date. To achieve the targeted test accuracy, the sensitive space accelerometer will use the very soft space environment provided by a quasi-drag-free floating capsule and long-time observation of the free-fall mass motion for integration of the measurements over 20 orbits. In this work, we describe the design and capability of the differential accelerometer to test weak space acceleration. Modeling and simulation results of the electrostatic suspension and electrostatic motor are presented based on attainable space microgravity condition. Noise evaluation shows that the electrostatic actuation and residual non-gravitational acceleration are two major noise sources. The evaluated differential acceleration noise is 1.01 × 10(-9) m/s²/Hz(1/2) at the NEP signal frequency of 0.182 mHz, by neglecting small acceleration disturbances. The preliminary work on development of the first instrument prototype is introduced for on-ground technological assessments. This development has already confirmed several crucial fabrication processes and measurement techniques and it will open the way to the construction of the final differential space accelerometer. PMID:27517927

  15. Convergent Validity of Four Accelerometer Cutpoints with Direct Observation of Preschool Children's Outdoor Physical Activity

    Science.gov (United States)

    Kahan, David; Nicaise, Virginie; Reuben, Karen

    2013-01-01

    Purpose: More than one fifth of American preschool-aged children are classified as overweight/obese. Increasing physical activity is one means of slowing/reversing progression to overweight or obesity. Measurement of physical activity in this age group relies heavily on motion sensors such as accelerometers. Output is typically interpreted through…

  16. Design and Fabrication of a Differential Electrostatic Accelerometer for Space-Station Testing of the Equivalence Principle

    Science.gov (United States)

    Han, Fengtian; Liu, Tianyi; Li, Linlin; Wu, Qiuping

    2016-01-01

    The differential electrostatic space accelerometer is an equivalence principle (EP) experiment instrument proposed to operate onboard China’s space station in the 2020s. It is designed to compare the spin-spin interaction between two rotating extended bodies and the Earth to a precision of 10−12, which is five orders of magnitude better than terrestrial experiment results to date. To achieve the targeted test accuracy, the sensitive space accelerometer will use the very soft space environment provided by a quasi-drag-free floating capsule and long-time observation of the free-fall mass motion for integration of the measurements over 20 orbits. In this work, we describe the design and capability of the differential accelerometer to test weak space acceleration. Modeling and simulation results of the electrostatic suspension and electrostatic motor are presented based on attainable space microgravity condition. Noise evaluation shows that the electrostatic actuation and residual non-gravitational acceleration are two major noise sources. The evaluated differential acceleration noise is 1.01 × 10−9 m/s2/Hz1/2 at the NEP signal frequency of 0.182 mHz, by neglecting small acceleration disturbances. The preliminary work on development of the first instrument prototype is introduced for on-ground technological assessments. This development has already confirmed several crucial fabrication processes and measurement techniques and it will open the way to the construction of the final differential space accelerometer. PMID:27517927

  17. Detection of knee instability using accelerometers experimental test and potential use in the control of FES-assisted parplegic standing

    NARCIS (Netherlands)

    Veltink, Peter H.; Franken, Henry M.; Verboon, Ard W.; Boom, Herman B.K.

    1993-01-01

    We propose a knee instability detector for standing using two uni-axial accelerometers, tangentially placed on the upper leg. This detector may be used as a part of the finite state artificial reflex control strategy for paraplegic standing with minimal quadriceps stimulation, as proposed by Mulder

  18. Influence of allowable interruption period on estimates of accelerometer wear time and sedentary time in older adults

    Science.gov (United States)

    Mailey, Emily L.; Gothe, Neha P.; Wójcicki, Thomas R.; Szabo, Amanda N.; Olson, Erin A.; Mullen, Sean P.; Fanning, Jason T.; Motl, Robert W.; McAuley, Edward

    2013-01-01

    The criteria one uses to reduce accelerometer data can profoundly influence the interpretation of research outcomes. The purpose of this study was to examine the influence of three different interruption periods (i.e., 20, 30, and 60 minutes) on the amount of data retained for analyses and estimates of sedentary time among older adults. Older adults (N=311; Mage=71.1) wore an accelerometer for seven days and reported wear time on an accelerometer log. Accelerometer data were downloaded and scored using 20, 30, and 60-minute interruption periods. Estimates of wear time derived using each interruption period were compared to self-reported wear time, and descriptive statistics were used to compare estimates of sedentary time. Results showed a longer interruption period (i.e., 60 minutes) yields the largest sample size and the closest approximation of self-reported wear time. A short interruption period (i.e., 20 minutes) is likely to underestimate sedentary time among older adults. PMID:23752299

  19. An intermediate-level physics laboratory: A system of two coupled oscillators with low-cost accelerometers

    CERN Document Server

    Lamont, Mary

    2012-01-01

    We describe an intermediate-level physics experiment beyond the first-year, which uses versatile, low-cost accelerometers (Wiimotes for the Nintendo Wii gaming system) and scientific-computing software for numerical data analysis. It is designed to help students to develop better understanding of a system of coupled oscillators and Fourier transform.

  20. Design and Fabrication of a Differential Electrostatic Accelerometer for Space-Station Testing of the Equivalence Principle.

    Science.gov (United States)

    Han, Fengtian; Liu, Tianyi; Li, Linlin; Wu, Qiuping

    2016-08-10

    The differential electrostatic space accelerometer is an equivalence principle (EP) experiment instrument proposed to operate onboard China's space station in the 2020s. It is designed to compare the spin-spin interaction between two rotating extended bodies and the Earth to a precision of 10(-12), which is five orders of magnitude better than terrestrial experiment results to date. To achieve the targeted test accuracy, the sensitive space accelerometer will use the very soft space environment provided by a quasi-drag-free floating capsule and long-time observation of the free-fall mass motion for integration of the measurements over 20 orbits. In this work, we describe the design and capability of the differential accelerometer to test weak space acceleration. Modeling and simulation results of the electrostatic suspension and electrostatic motor are presented based on attainable space microgravity condition. Noise evaluation shows that the electrostatic actuation and residual non-gravitational acceleration are two major noise sources. The evaluated differential acceleration noise is 1.01 × 10(-9) m/s²/Hz(1/2) at the NEP signal frequency of 0.182 mHz, by neglecting small acceleration disturbances. The preliminary work on development of the first instrument prototype is introduced for on-ground technological assessments. This development has already confirmed several crucial fabrication processes and measurement techniques and it will open the way to the construction of the final differential space accelerometer.

  1. Sensitivity optimization of a monolithic high-shock three-axis piezoresistive accelerometer with single sensing element

    Institute of Scientific and Technical Information of China (English)

    SONG Ping; LI QingZhou; LI KeJie

    2009-01-01

    There exist several difficulties in the design of monolithic high-shock three-axis accelerometer, such as high g overload, transverse overload and the cross coupling in three dimensions, etc. It is necessary to optimize the sensitivity to improve the performance of the accelerometer. For the monolithic high-shock three-axis accelerometer, the complexity of the sensitivity optimization is that it should consider not only the sensitivity difference between different axes but also the elimination of cross-coupling outputs, together with the natural frequency, structural integrity and high g overload. In this paper, the optimization process for decreasing the difference of the sensitivities between different axes of a monolithic high-shock three-axis piezoresistive accelerometer with single sensing element is established. The optimization is conducted in the condition of 100000 g acceleration by two methods-the method based on the optimization module of ANSYS and the ACO (ant colony optimiza-tion) method. The comparison between un-optimized and optimized models proves the efficiency of the optimization methods. In addition, the optimization results show that the ACO method combined with the FEA (finite element analysis) is much more efficient than the method based on the optimization module of ANSYS for the structural optimization problem. And the ACO method can be widely used in the optimization problem of the sensing elements with complicated structure.

  2. Neckband or backpack? Differences in tag design and their effects on GPS/accelerometer tracking results in large waterbirds

    NARCIS (Netherlands)

    Kölzsch, Andrea; Neefjes, Marjolein; Barkway, Jude; Müskens, G.J.D.M.; Langevelde, van Frank; Boer, de Willem F.; Prins, Herbert H.T.; Cresswell, Brian H.; Nolet, Bart A.

    2016-01-01

    Background
    GPS and accelerometer tracking presently revolutionises the fields of ecology and animal behaviour. However, the effects of tag characteristics like weight, attachment and data quality on study outcomes and animal welfare are important to consider. In this study, we compare how differ

  3. Neckband or backpack? Differences in tag design and their effects on GPS/accelerometer tracking results in large waterbirds.

    NARCIS (Netherlands)

    Kölzsch, Andrea; Neefjes, M.; Barkway, J.; Müskens, G.J.D.M.; van Langevelde, F.; De Boer, W.F.; Prins, H.H.T.; Cresswell, B.H.; Nolet, B.A.

    2016-01-01

    Background GPS and accelerometer tracking presently revolutionises the fields of ecology and animal behaviour. However, the effects of tag characteristics like weight, attachment and data quality on study outcomes and animal welfare are important to consider. In this study, we compare how different

  4. Improvements in the Measurement of Physical Activity in Childhood Obesity Research; Lessons from Large Studies of Accelerometers

    Directory of Open Access Journals (Sweden)

    Andy Ness

    2008-01-01

    Full Text Available Advances in technology have improved our ability to measure physical activity in free-living humans. In the last few years, several large epidemiological studies in Europe and the United States have used accelerometers to assess physical activity in children and adolescents. The use of accelerometers to study physical activity has presented some challenges on how to summarise and interpret the data that they generate, however these studies are providing important information on the levels and patterns of physical activity among children and adolescents. Some studies have reported that few children and adolescents appear to meet the recommended minimum of 60 minutes of moderate to vigorous activity per day. Accelerometers have also allowed examination of the relationships between physical activity and health outcomes like obesity and other chronic disease risk factors such as insulin resistance, aerobic fitness, blood lipids and blood pressure. Use of accelerometers allows such relationships to be estimated with a precision that was previously impossible with self-report measures of physical activity. Such information is already advancing our understanding of the role that physical activity plays in preventing childhood obesity and cardiovascular disease risk.

  5. Design and initial characterization of a compact, ultra high vacuum compatible, low frequency, tilt accelerometer

    Energy Technology Data Exchange (ETDEWEB)

    O’Toole, A., E-mail: amandajotoole@gmail.com, E-mail: riccardo.desalvo@gmail.com [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, 405 Hilgard Ave, Los Angeles, California 90095 (United States); Peña Arellano, F. E. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Rodionov, A. V.; Kim, C. [California Institute of Technology, Pasadena, California 91125 (United States); Shaner, M.; Asadoor, M. [Mayfield Senior School, 500 Bellefontaine Street Pasadena, California 91105 (United States); Sobacchi, E. [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Dergachev, V.; DeSalvo, R., E-mail: amandajotoole@gmail.com, E-mail: riccardo.desalvo@gmail.com [LIGO Laboratory, California Institute of Technology, MS 100-36, Pasadena, California 91125 (United States); Bhawal, A. [Arcadia High School, 180 Campus Drive, Arcadia, California 91007 (United States); Gong, P. [Department of Precision Instrument, Tsinghua University, Beijing 100084 (China); Lottarini, A. [Department of Computer Science, University of Pisa, Largo B. Pontecorvo 3, 56127 Pisa (Italy); Minenkov, Y. [Sezione INFN Tor Vergata, via della Ricerca Scientfica 1, 00133 Roma (Italy); Murphy, C. [School of Physics, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, Western Australia 6009 (Australia)

    2014-07-15

    A compact tilt accelerometer with high sensitivity at low frequency was designed to provide low frequency corrections for the feedback signal of the Advanced Laser Interferometer Gravitational Wave Observatory active seismic attenuation system. It has been developed using a Tungsten Carbide ceramic knife-edge hinge designed to avoid the mechanical 1/f noise believed to be intrinsic in polycrystalline metallic flexures. Design and construction details are presented; prototype data acquisition and control limitations are discussed. The instrument's characterization reported here shows that the hinge is compatible with being metal-hysteresis-free, and therefore also free of the 1/f noise generated by the dislocation Self-Organized Criticality in the metal. A tiltmeter of this kind will be effective to separate the ground tilt component from the signal of horizontal low frequency seismometers, and to correct the ill effects of microseismic tilt in advanced seismic attenuation systems.

  6. User-independent accelerometer-based gesture recognition for mobile devices

    Directory of Open Access Journals (Sweden)

    Eduardo METOLA

    2013-07-01

    Full Text Available Many mobile devices embed nowadays inertial sensors. This enables new forms of human-computer interaction through the use of gestures (movements performed with the mobile device as a way of communication. This paper presents an accelerometer-based gesture recognition system for mobile devices which is able to recognize a collection of 10 different hand gestures. The system was conceived to be light and to operate in a user-independent manner in real time. The recognition system was implemented in a smart phone and evaluated through a collection of user tests, which showed a recognition accuracy similar to other state-of-the art techniques and a lower computational complexity. The system was also used to build a human-robot interface that enables controlling a wheeled robot with the gestures made with the mobile phone

  7. User-independent accelerometer-based gesture recognition for mobile devices

    Directory of Open Access Journals (Sweden)

    Xian WANG

    2012-12-01

    Full Text Available Many mobile devices embed nowadays inertial sensors. This enables new forms of human-computer interaction through the use of gestures (movements performed with the mobile device as a way of communication. This paper presents an accelerometer-based gesture recognition system for mobile devices which is able to recognize a collection of 10 different hand gestures. The system was conceived to be light and to operate in a user-independent manner in real time. The recognition system was implemented in a smart phone and evaluated through a collection of user tests, which showed a recognition accuracy similar to other state-of-the art techniques and a lower computational complexity. The system was also used to build a human-robot interface that enables controlling a wheeled robot with the gestures made with the mobile phone

  8. Design and Modeling of a Three-axis Piezoresistive Microelectronic Accelerometer

    Science.gov (United States)

    Benmoussa, N.; Benichou, A.; Ghaffour, K.; Benyoucef, B.

    Micro-electro-mechanical systems (MEMS) for automotive industry and biomedical applications (BioMEMS) have the fastest growth rate within the MEMS market. The Microsystems job market imposes to research laboratories and universities to respond by increasing the quality of MEMS engineering and informatics interdisciplinary training programs. In this fact, our work consists to study and develop a three-axis piezoresistive accelerometer having uniform sensitivities along to three axes. This sensor which is made of a heavy proof mass and four long beams, allow us to obtain high sensitivities, by reducing the resonant frequencies. Uniform axial sensitivities, with a transverse sensitivity, could be obtained using a three-axis sensor. The stress analysis of this sensor was performed in order to determine the positions of the piezoresistances, in the four flexure beams.

  9. An improved quaternion Gauss-Newton algorithm for attitude determination using magnetometer and accelerometer

    Institute of Scientific and Technical Information of China (English)

    Liu Fei; Li Jie; Wang Haifu; Liu Chang

    2014-01-01

    For the vector attitude determination, the traditional optimal algorithms which are based on quaternion estimator (QUEST) measurement noise model are complicated for just two observa-tions. In our application, the magnetometer and accelerometer are not two comparable kinds of sen-sors and both are not small field-of-view sensors as well. So in this paper a new unit measurement model is derived. According to the Wahba problem, the optimal weights for each measurement are obtained by the error variance researches. Then an improved quaternion Gauss-Newton method is presented and adopted to acquire attitude. Eventually, simulation results and experimental valida-tion employed to test the proposed method demonstrate the usefulness of the improved algorithm.

  10. A study of the earth's free core nutation using international deployment of accelerometers gravity data

    Science.gov (United States)

    Cummins, Phil R.; Wahr, John M.

    1993-01-01

    In this study we consider the influence of the earth's free core nutation (FCN) on diurnal tidal admittance estimates for 11 stations of the globally distributed International Deployment of Accelerometers network. The FCN causes a resonant enhancement of the diurnal admittances which can be used to estimate some properties of the FCN. Estimations of the parameters describing the FCN (period, Q, and resonance strength) are made using data from individual stations and many stations simultaneously. These yield a result for the period of 423-452 sidereal days, which is shorter than theory predicts but is in agreement with many previous studies and suggests that the dynamical ellipticity of the core may be greater than its hydrostatic value.

  11. Earth Gravity Field Recovered from CHAMP Science Orbit and Accelerometer Data

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xuhua; WU Bin; PENG Bibo; XU Houze

    2006-01-01

    The earth gravity field model CDS01S of degree and order 36 has been recovered from the post processed Science Orbits and on-board accelerometer data of GFZ's CHAMP satellite. The model resolves the geoid with an accuracy of better than 4 cm at a resolution of 700 km half-wavelength. By using the degree difference variances of geopotential coefficients to compare the model CDS01S with EIGEN3P, EIGEN1S and EGM96, the result indicates that the coefficients of CDS01S are most close to those of EIGEN3P. The result of the comparison between the accuracies of geopotential coefficients in the above models, indicates that the accuracy of coefficients in CDS01S is higher than that in EGM96.The geoid undulations of CDS01S and GGM01C up to 30 degrees are calculated and the standard deviation is 4.7 cm between them.

  12. Wavelet based approach for posture transition estimation using a waist worn accelerometer.

    Science.gov (United States)

    Bidargaddi, Niranjan; Klingbeil, Lasse; Sarela, Antti; Boyle, Justin; Cheung, Vivian; Yelland, Catherine; Karunanithi, Mohanraj; Gray, Len

    2007-01-01

    The ability to rise from a chair is considered to be important to achieve functional independence and quality of life. This sit-to-stand task is also a good indicator to assess condition of patients with chronic diseases. We developed a wavelet based algorithm for detecting and calculating the durations of sit-to-stand and stand-to-sit transitions from the signal vector magnitude of the measured acceleration signal. The algorithm was tested on waist worn accelerometer data collected from young subjects as well as geriatric patients. The test demonstrates that both transitions can be detected by using wavelet transformation applied to signal magnitude vector. Wavelet analysis produces an estimate of the transition pattern that can be used to calculate the transition duration that further gives clinically significant information on the patients condition. The method can be applied in a real life ambulatory monitoring system for assessing the condition of a patient living at home. PMID:18002349

  13. An improved quaternion Gauss–Newton algorithm for attitude determination using magnetometer and accelerometer

    Directory of Open Access Journals (Sweden)

    Liu Fei

    2014-08-01

    Full Text Available For the vector attitude determination, the traditional optimal algorithms which are based on quaternion estimator (QUEST measurement noise model are complicated for just two observations. In our application, the magnetometer and accelerometer are not two comparable kinds of sensors and both are not small field-of-view sensors as well. So in this paper a new unit measurement model is derived. According to the Wahba problem, the optimal weights for each measurement are obtained by the error variance researches. Then an improved quaternion Gauss–Newton method is presented and adopted to acquire attitude. Eventually, simulation results and experimental validation employed to test the proposed method demonstrate the usefulness of the improved algorithm.

  14. Swarm accelerometer data processing from raw accelerations to thermospheric neutral densities

    DEFF Research Database (Denmark)

    Siemes, Christian; da Encarnacao, Joao de Teixeira; Doornbos, Eelco;

    2016-01-01

    , the most prominent being slow temperature-induced bias variations and sudden bias changes. In this paper, we describe the new, improved four-stage processing that is applied for transforming the disturbed acceleration measurements into scientifically valuable thermospheric neutral densities. In the first...... stage, the sudden bias changes in the acceleration measurements are manually removed using a dedicated software tool. The second stage is the calibration of the accelerometer measurements against the non-gravitational accelerations derived from the GPS receiver, which includes the correction...... for the slow temperature-induced bias variations. The identification of validity periods for calibration and correction parameters is part of the second stage. In the third stage, the calibrated and corrected accelerations are merged with the non-gravitational accelerations derived from the observations...

  15. Non-Parametric Bayesian Human Motion Recognition Using a Single MEMS Tri-Axial Accelerometer

    Directory of Open Access Journals (Sweden)

    M. Ejaz Ahmed

    2012-09-01

    Full Text Available In this paper, we propose a non-parametric clustering method to recognize the number of human motions using features which are obtained from a single microelectromechanical system (MEMS accelerometer. Since the number of human motions under consideration is not known a priori and because of the unsupervised nature of the proposed technique, there is no need to collect training data for the human motions. The infinite Gaussian mixture model (IGMM and collapsed Gibbs sampler are adopted to cluster the human motions using extracted features. From the experimental results, we show that the unanticipated human motions are detected and recognized with significant accuracy, as compared with the parametric Fuzzy C-Mean (FCM technique, the unsupervised K-means algorithm, and the non-parametric mean-shift method.

  16. Non-parametric Bayesian human motion recognition using a single MEMS tri-axial accelerometer.

    Science.gov (United States)

    Ahmed, M Ejaz; Song, Ju Bin

    2012-01-01

    In this paper, we propose a non-parametric clustering method to recognize the number of human motions using features which are obtained from a single microelectromechanical system (MEMS) accelerometer. Since the number of human motions under consideration is not known a priori and because of the unsupervised nature of the proposed technique, there is no need to collect training data for the human motions. The infinite Gaussian mixture model (IGMM) and collapsed Gibbs sampler are adopted to cluster the human motions using extracted features. From the experimental results, we show that the unanticipated human motions are detected and recognized with significant accuracy, as compared with the parametric Fuzzy C-Mean (FCM) technique, the unsupervised K-means algorithm, and the non-parametric mean-shift method. PMID:23201992

  17. Accelerometer-measured daily physical activity related to aerobic fitness in children and adolescents

    DEFF Research Database (Denmark)

    Dencker, Magnus; Andersen, Lars Bo

    2011-01-01

    . The purpose of this paper is to summarise recently published data on the relationship between daily physical activity, as measured by accelerometers, and [Vdot]O(2PEAK) in children and adolescents. A PubMed search was performed on 29 October 2010 to identify relevant articles. Studies were considered relevant......Maximum oxygen uptake ([Vdot]O(2PEAK)) is generally considered to be the best single marker for aerobic fitness. While a positive relationship between daily physical activity and aerobic fitness has been established in adults, the relationship appears less clear in children and adolescents...... if they included measurement of daily physical activity by accelerometry and related to a [Vdot]O(2PEAK) either measured directly at a maximal exercise test or estimated from maximal power output. A total of nine studies were identified, with a total number of 6116 children and adolescents investigated. Most...

  18. Tyre contact length on dry and wet road surfaces measured by three-axial accelerometer

    Science.gov (United States)

    Matilainen, Mika; Tuononen, Ari

    2015-02-01

    We determined the tyre contact length on dry and wet roads by measuring the accelerations of the inner liner with a three-axial accelerometer. The influence of the tyre pressure, driving velocity, and tread depth on the contact length was studied in both types of road surface conditions. On dry asphalt the contact length was almost constant, regardless of the driving velocity. On wet asphalt the presence of water could be detected even at low driving velocities (e.g. 20 km/h for a worn tyre) as the contact length began to decrease from that found in the dry asphalt situation. In addition to improving the performance of active safety systems and driver warning systems, the contact length information could be beneficial for classifying and studying the aquaplaning behaviour of tyres.

  19. Design and initial characterization of a compact, ultra high vacuum compatible, low frequency, tilt accelerometer

    International Nuclear Information System (INIS)

    A compact tilt accelerometer with high sensitivity at low frequency was designed to provide low frequency corrections for the feedback signal of the Advanced Laser Interferometer Gravitational Wave Observatory active seismic attenuation system. It has been developed using a Tungsten Carbide ceramic knife-edge hinge designed to avoid the mechanical 1/f noise believed to be intrinsic in polycrystalline metallic flexures. Design and construction details are presented; prototype data acquisition and control limitations are discussed. The instrument's characterization reported here shows that the hinge is compatible with being metal-hysteresis-free, and therefore also free of the 1/f noise generated by the dislocation Self-Organized Criticality in the metal. A tiltmeter of this kind will be effective to separate the ground tilt component from the signal of horizontal low frequency seismometers, and to correct the ill effects of microseismic tilt in advanced seismic attenuation systems

  20. Two self-test methods applied to an inertial system problem. [estimating gyroscope and accelerometer bias

    Science.gov (United States)

    Willsky, A. S.; Deyst, J. J.; Crawford, B. S.

    1975-01-01

    The paper describes two self-test procedures applied to the problem of estimating the biases in accelerometers and gyroscopes on an inertial platform. The first technique is the weighted sum-squared residual (WSSR) test, with which accelerator bias jumps are easily isolated, but gyro bias jumps are difficult to isolate. The WSSR method does not take full advantage of the knowledge of system dynamics. The other technique is a multiple hypothesis method developed by Buxbaum and Haddad (1969). It has the advantage of directly providing jump isolation information, but suffers from computational problems. It might be possible to use the WSSR to detect state jumps and then switch to the BH system for jump isolation and estimate compensation.

  1. Tooth brushing pattern classification using three-axis accelerometer and magnetic sensor for smart toothbrush.

    Science.gov (United States)

    Lee, Kang-Hwi; Lee, Jeong-Whan; Kim, Kyeong-Seop; Kim, Dong-Jun; Kim, Kyungho; Yang, Heui-Kyung; Jeong, Keesam; Lee, Byungchae

    2007-01-01

    The concept of intelligent toothbrush, capable of monitoring brushing motion, orientation through the grip axis, during toothbrushing was suggested in our previous study. In this study, we describe a tooth brushing pattern classification algorithm using three-axis accelerometer and three-axis magnetic sensor. We have found that inappropriate tooth brushing pattern showed specific moving patterns. In order to trace the position and orientation of toothbrush in a mouth, we need to know absolute coordinate information of toothbrush. By applying tilt-compensated azimuth (heading) calculation algorithm, which is generally used in small telematics devices, we could find the inclination and orientation information of toothbrush. To assess the feasibility of the proposed algorithm, 8 brushing patterns were preformed by 6 individual healthy subjects. The proposed algorithm showed the detection ratio of 98%. This study showed that the proposed monitoring system was conceived to aid dental care personnel in patient education and instruction in oral hygiene regarding brushing style. PMID:18002931

  2. A Single Accelerometer based Wireless Embedded System for Predefined Dynamic Gesture Recognition

    Science.gov (United States)

    Parsani, Rahul; Singh, Karandeep

    The use of hand gestures provides an attractive alternative to cumbersome interface devices for human-computer interaction. A complete embedded system which facilitates the data acquisition, analysis, recognition, and the transmission wirelessly, of human dynamic gestures to a computer, is described. An intuitive algorithm for processing the accelerometer data was implemented and tested. This method permits all the analysis to be done by the embedded system processor. The system is capable of recognizing gestures involving a combination of straight line motions in three dimensions. These gestures are then used to control a host computer which executes tasks based on the gesture received. A sample application showing how the gestures can be mapped to the English alphabet is also shown.

  3. Effects of dielectric charging on the output voltage of a capacitive accelerometer

    Science.gov (United States)

    Qu, Hao; Yu, Huijun; Zhou, Wu; Peng, Bei; Peng, Peng; He, Xiaoping

    2016-11-01

    Output voltage drifting observed in one typical capacitive microelectromechanical system (MEMS) accelerometer is discussed in this paper. Dielectric charging effect is located as one of the major determinants of this phenomenon through a combination of experimental and theoretical studies. A theoretical model for the electromechanical effects of the dielectric surface charges within the electrode gap is established to analyze the dielectric charge effect on the output voltage. Observations of output voltage drift against time are fitted to this model in order to estimate the possible dielectric layer thickness. Meanwhile, Auger electron spectroscopy is carried out to analyze the electrode surface material composition and confirms a mixture layer of dielectric SiO2 and Si with a thickness about 5 nm, which is very close to the model estimation. In addition, observation of time-varing output drift in the variable bias voltage experiment indicates the movement of dielectric charge can be controlled by the applied electric field.

  4. Speed estimation from a tri-axial accelerometer using neural networks.

    Science.gov (United States)

    Song, Yoonseon; Shin, Seungchul; Kim, Seunghwan; Lee, Doheon; Lee, Kwang H

    2007-01-01

    We propose a speed estimation method with human body accelerations measured on the chest by a tri-axial accelerometer. To estimate the speed we segmented the acceleration signal into strides measuring stride time, and applied two neural networks into the patterns parameterized from each stride calculating stride length. The first neural network determines whether the subject walks or runs, and the second neural network with different node interactions according to the subject's status estimates stride length. Walking or running speed is calculated with the estimated stride length divided by the measured stride time. The neural networks were trained by patterns obtained from 15 subjects and then validated by 2 untrained subjects' patterns. The result shows good agreement between actual and estimated speeds presenting the linear correlation coefficient r=0.9874. We also applied the method to the real field and track data.

  5. Development of the high sensitivity GRADIO accelerometers - The Aristoteles gradiometer mission preparation

    Science.gov (United States)

    Bernard, A.; Touboul, P.

    ESA and NASA are preparing the cooperative geopotential mission ARISTOTELES that will combine, for the global and fine recovery of the earth's gravity field, gradiometric measurements on board a dedicated satellite at 200-km altitude and satellite-to-satellite tracking using GPS network. The gradiometer required accuracy is 0.01 Eotvos, leading for the GRADIO ultrasensitive accelerometers composing this instrument to a resolution of 5 x 10 exp -12 per sq ms in the bandwidth (5 x 10 exp -3 Hz, 0.125 Hz) in microgravity conditions. Two laboratory models and a specific test bench have been realized. In spite of the presence of gravity and of the seismic noise, differential tests at a level of better than one nanoG are achieved on ground.

  6. Design and initial characterization of a compact, ultra high vacuum compatible, low frequency, tilt accelerometer

    Science.gov (United States)

    O'Toole, A.; Peña Arellano, F. E.; Rodionov, A. V.; Shaner, M.; Sobacchi, E.; Dergachev, V.; DeSalvo, R.; Asadoor, M.; Bhawal, A.; Gong, P.; Kim, C.; Lottarini, A.; Minenkov, Y.; Murphy, C.

    2014-07-01

    A compact tilt accelerometer with high sensitivity at low frequency was designed to provide low frequency corrections for the feedback signal of the Advanced Laser Interferometer Gravitational Wave Observatory active seismic attenuation system. It has been developed using a Tungsten Carbide ceramic knife-edge hinge designed to avoid the mechanical 1/f noise believed to be intrinsic in polycrystalline metallic flexures. Design and construction details are presented; prototype data acquisition and control limitations are discussed. The instrument's characterization reported here shows that the hinge is compatible with being metal-hysteresis-free, and therefore also free of the 1/f noise generated by the dislocation Self-Organized Criticality in the metal. A tiltmeter of this kind will be effective to separate the ground tilt component from the signal of horizontal low frequency seismometers, and to correct the ill effects of microseismic tilt in advanced seismic attenuation systems.

  7. Curve aligning approach for gait authentication based on a wearable accelerometer

    International Nuclear Information System (INIS)

    Gait authentication based on a wearable accelerometer is a novel biometric which can be used for identity identification, medical rehabilitation and early detection of neurological disorders. The method for matching gait patterns tells heavily on authentication performances. In this paper, curve aligning is introduced as a new method for matching gait patterns and it is compared with correlation and dynamic time warping (DTW). A support vector machine (SVM) is proposed to fuse pattern-matching methods in a decision level. Accelerations collected from ankles of 22 walking subjects are processed for authentications in our experiments. The fusion of curve aligning with backward–forward accelerations and DTW with vertical accelerations promotes authentication performances substantially and consistently. This fusion algorithm is tested repeatedly. Its mean and standard deviation of equal error rates are 0.794% and 0.696%, respectively, whereas among all presented non-fusion algorithms, the best one shows an EER of 3.03%. (paper)

  8. An automated CAE system for multidisciplinary structural design: its application to micro accelerometer

    International Nuclear Information System (INIS)

    This paper describes a new computer-aided engineering system for multidisciplinary structural design. An automatic finite element mesh generation technique, based on fuzzy knowledge processing and computational geometry, is incorporated into the system, together with one of the commercial finite element analysis codes. A bubble is generated if its distance from existing bubble points is similar to the bubble-spacing function at the point. The bubble-spacing function is well controlled by fuzzy knowledge processing. The Delaunay method is employed as a basic tool for element generation. Automatic finite element generation for three-dimensional MEMS holds great benefits for analyses. An optimum design solution or satisfactory solutions will be automatically searched using the genetic algorithms modified for real search space, together with the automated finite element analysis system. A novel CAE system was developed, and successfully applied to the shape design of a micro accelerometer based on a tunneling current concept

  9. Analysis of walking improvement with dynamic shoe insoles, using two accelerometers

    Science.gov (United States)

    Tsuruoka, Yuriko; Tamura, Yoshiyasu; Shibasaki, Ryosuke; Tsuruoka, Masako

    2005-07-01

    The orthopedics at the rehabilitation hospital found that disorders caused by sports injuries to the feet or caused by lower-back are improved by wearing dynamic shoe insoles, these improve walking balance and stability. However, the relationship of the lower-back and knees and the rate of increase in stability were not quantitatively analyzed. In this study, using two accelerometers, we quantitatively analyzed the reciprocal spatiotemporal contributions between the lower-back and knee of patients with left lower-back pain by means of Relative Power Contribution Analysis. When the insoles were worn, the contribution of the left and right knee relative to the left lower-back pain was up to 26% ( panalysis of the left and right knee decreased by up to 67% ( p<0.05). This shows an increase in stability.

  10. A Monolithic High-G SOI-MEMS Accelerometer for Measuring Projectile Launch and Flight Accelerations

    Directory of Open Access Journals (Sweden)

    Bradford S. Davis

    2006-01-01

    Full Text Available Analog Devices (ADI has designed and fabricated a monolithic high-g acceleration sensor (ADXSTC3-HG fabricated with the ADI silicon-on-insulator micro-electro-mechanical system (SOI-MEMS process. The SOI-MEMS sensor structure has a thickness of 10 um, allowing for the design of inertial sensors with excellent cross-axis rejection. The high-g accelerometer discussed in this paper was designed to measure in-plane acceleration to 10,000 g while subjected to 100,000 g in the orthogonal axes. These requirements were intended to meet Army munition applications. The monolithic sensor was packaged in an 8-pin leadless chip carrier (LCC-8 and was successfully demonstrated by the US Army Research Laboratory (ARL as part of an inertial measurement unit during an instrumented flight experiment of artillery projectiles launched at 15,000 g.

  11. Relationship Between Accelerometer Load, Collisions, and Repeated High-Intensity Effort Activity in Rugby League Players.

    Science.gov (United States)

    Gabbett, Tim J

    2015-12-01

    Triaxial accelerometers have been critical in providing information on the high-acceleration, low-velocity movements that occur in team sports. In addition, these sensors have proven to be useful in quantifying the activities that do not involve the vertical acceleration associated with locomotion (e.g., tackling, on-ground wrestling, and grappling). This study investigated the relationship between Player Load (PL), 2D Player Load (2DPL), and Player Load Slow (PL Slow), collisions, and repeated high-intensity effort (RHIE) activity in rugby league players. One hundred and eighty-two rugby league players (age, 24.3 ± 3.3 years) participated in this study. Movement was recorded using a global positioning system unit sampling at 10 Hz and triaxial accelerometer sampling at 100 Hz. Analysis was completed during 26 matches (totaling 386 appearances). Pearson product-moment correlation coefficients were used to determine relationships between PL, 2DPL, and PL Slow and total collisions and RHIE activity. When all players were considered, weak relationships were found between PL and the number of collisions and RHIE bouts performed. However, PL was strongly associated (p ≤ 0.05) with total distance, low-speed activity, high-speed running distance, total collisions, and the number of RHIE bouts for forwards and hookers. Weak and typically insignificant relationships were found between PL, 2DPL, and PL Slow and the number of collisions and RHIE bouts performed by the adjustables and outside backs positional groups. The relationships between PL and the number of collisions and RHIE bouts are stronger in positions where contact and repeated-effort demands are high. From a practical perspective, these results suggest that PL, 2DPL, and PL Slow offer useful "real-time" measures of collision and RHIE activity, particularly in forwards and hookers, to inform interchange strategies and ensure players are training at an adequate intensity. PMID:26196661

  12. Using Wearable Accelerometers in a Community Service Context to Categorize Falling Behavior

    Directory of Open Access Journals (Sweden)

    Chia-Hsuan Lee

    2016-07-01

    Full Text Available In this paper, the Multiscale Entropy (MSE analysis of acceleration data collected from a wearable inertial sensor was compared with other features reported in the literature to observe falling behavior from the acceleration data, and traditional clinical scales to evaluate falling behavior. We use a fall risk assessment over a four-month period to examine >65 year old participants in a community service context using simple clinical tests, including the Short Form Berg Balance Scale (SFBBS, Timed Up and Go test (TUG, and the Short Portable Mental Status Questionnaire (SPMSQ, with wearable accelerometers for the TUG test. We classified participants into fallers and non-fallers to (1 compare the features extracted from the accelerometers and (2 categorize fall risk using statistics from TUG test results. Combined, TUG and SFBBS results revealed defining features were test time, Slope(A and slope(B in Sit(A-to-stand(B, and range(A and slope(B in Stand(B-to-sit(A. Of (1 SPMSQ; (2 TUG and SPMSQ; and (3 BBS and SPMSQ results, only range(A in Stand(B-to-sit(A was a defining feature. From MSE indicators, we found that whether in the X, Y or Z direction, TUG, BBS, and the combined TUG and SFBBS are all distinguishable, showing that MSE can effectively classify participants in these clinical tests using behavioral actions. This study highlights the advantages of body-worn sensors as ordinary and low cost tools available outside the laboratory. The results indicated that MSE analysis of acceleration data can be used as an effective metric to categorize falling behavior of community-dwelling elderly. In addition to clinical application, (1 our approach requires no expert physical therapist, nurse, or doctor for evaluations and (2 fallers can be categorized irrespective of the critical value from clinical tests.

  13. Characteristics of satellite accelerometer measurements of thermospheric neutral winds at high latitudes

    Science.gov (United States)

    Doornbos, E.; Ridley, A. J.; Cnossen, I.; Aruliah, A. L.; Foerster, M.

    2015-12-01

    Thermospheric neutral winds play an important part in the coupled thermosphere-ionosphere system at high latitudes. Neutral wind speeds have been derived from the CHAMP and GOCE satellites, which carried precise accelerometers in low Earth orbits. Due to the need to simultaneously determine thermosphere neutral density from the accelerometer in-track measurements, only information on the wind component in the cross-track direction, perpendicular to the flight direction can be derived. However, contrary to ground-based Fabry-Perot interferometer and scanning Doppler imager observations of the thermosphere wind, these satellite-based measurements provide equally distributed coverage over both hemispheres. The sampling of seasonal and local time variations depend on the precession rate of the satellite's orbital plane, with CHAMP covering about 28 cycles of 24-hour local solar time coverage, during its 10 year mission (2000-2010), while the near sun-synchronous orbit of GOCE resulted in a much more limited local time coverage ranging from 6:20 to 8:00 (am and pm), during a science mission duration of 4 years (2009-2013). For this study, the wind data from both CHAMP and GOCE have been analysed in terms of seasonal variations and geographic and geomagnetic local solar time and latitude coordinates, in order to make statistical comparisons for both the Northern and Southern polar areas. The wind data from both satellites were studied independently and in combination, in order to investigate how the strengths and weaknesses of the instruments and orbit parameters of these missions affect investigations of interhemispheric differences. Finally, the data have been compared with results from coupled ionosphere-thermosphere models and from ground-based FPI and SDI measurements.

  14. Development of an accelerometer-linked online intervention system to promote physical activity in adolescents.

    Directory of Open Access Journals (Sweden)

    Nicole Guthrie

    Full Text Available Most adolescents do not achieve the recommended levels of moderate-to-vigorous physical activity (MVPA, placing them at increased risk for a diverse array of chronic diseases in adulthood. There is a great need for scalable and effective interventions that can increase MVPA in adolescents. Here we report the results of a measurement validation study and a preliminary proof-of-concept experiment testing the impact of Zamzee, an accelerometer-linked online intervention system that combines proximal performance feedback and incentive motivation features to promote MVPA. In a calibration study that parametrically varied levels of physical activity in 31 12-14 year-old children, the Zamzee activity meter was shown to provide a valid measure of MVPA (sensitivity in detecting MVPA = 85.9%, specificity = 97.5%, and r = .94 correspondence with the benchmark RT3 accelerometer system; all p < .0001. In a subsequent randomized controlled multi-site experiment involving 182 middle school-aged children assessed for MVPA over 6 wks, intent-to-treat analyses found that those who received access to the Zamzee intervention had average MVPA levels 54% greater than those of a passive control group (p < 0.0001 and 68% greater than those of an active control group that received access to a commercially available active videogame (p < .0001. Zamzee's effects on MVPA did not diminish significantly over the course of the 6-wk study period, and were statistically significant in both females and males, and in normal- vs. high-BMI subgroups. These results provide promising initial indications that combining the Zamzee activity meter with online proximal performance feedback and incentive motivation features can positively impact MVPA levels in adolescents.

  15. A Novel, Open Access Method to Assess Sleep Duration Using a Wrist-Worn Accelerometer.

    Directory of Open Access Journals (Sweden)

    Vincent T van Hees

    Full Text Available Wrist-worn accelerometers are increasingly being used for the assessment of physical activity in population studies, but little is known about their value for sleep assessment. We developed a novel method of assessing sleep duration using data from 4,094 Whitehall II Study (United Kingdom, 2012-2013 participants aged 60-83 who wore the accelerometer for 9 consecutive days, filled in a sleep log and reported sleep duration via questionnaire. Our sleep detection algorithm defined (nocturnal sleep as a period of sustained inactivity, itself detected as the absence of change in arm angle greater than 5 degrees for 5 minutes or more, during a period recorded as sleep by the participant in their sleep log. The resulting estimate of sleep duration had a moderate (but similar to previous findings agreement with questionnaire based measures for time in bed, defined as the difference between sleep onset and waking time (kappa = 0.32, 95%CI:0.29,0.34 and total sleep duration (kappa = 0.39, 0.36,0.42. This estimate was lower for time in bed for women, depressed participants, those reporting more insomnia symptoms, and on weekend days. No such group differences were found for total sleep duration. Our algorithm was validated against data from a polysomnography study on 28 persons which found a longer time window and lower angle threshold to have better sensitivity to wakefulness, while the reverse was true for sensitivity to sleep. The novelty of our method is the use of a generic algorithm that will allow comparison between studies rather than a "count" based, device specific method.

  16. Extracting respiratory information from seismocardiogram signals acquired on the chest using a miniature accelerometer

    International Nuclear Information System (INIS)

    Seismocardiography (SCG) is a non-invasive measurement of the vibrations of the chest caused by the heartbeat. SCG signals can be measured using a miniature accelerometer attached to the chest, and are thus well-suited for unobtrusive and long-term patient monitoring. Additionally, SCG contains information relating to both cardiovascular and respiratory systems. In this work, algorithms were developed for extracting three respiration-dependent features of the SCG signal: intensity modulation, timing interval changes within each heartbeat, and timing interval changes between successive heartbeats. Simultaneously with a reference respiration belt, SCG signals were measured from 20 healthy subjects and a respiration rate was estimated using each of the three SCG features and the reference signal. The agreement between each of the three accelerometer-derived respiration rate measurements was computed with respect to the respiration rate derived from the reference respiration belt. The respiration rate obtained from the intensity modulation in the SCG signal was found to be in closest agreement with the respiration rate obtained from the reference respiration belt: the bias was found to be 0.06 breaths per minute with a 95% confidence interval of −0.99 to 1.11 breaths per minute. The limits of agreement between the respiration rates estimated using SCG (intensity modulation) and the reference were within the clinically relevant ranges given in existing literature, demonstrating that SCG could be used for both cardiovascular and respiratory monitoring. Furthermore, phases of each of the three SCG parameters were investigated at four instances of a respiration cycle—start inspiration, peak inspiration, start expiration, and peak expiration—and during breath hold (apnea). The phases of the three SCG parameters observed during the respiration cycle were congruent with existing literature and physiologically expected trends. (paper)

  17. Damage detection methods on wind turbine blade testing with wired and wireless accelerometer sensors

    DEFF Research Database (Denmark)

    Mollineaux, Mark; Balafas, Konstantinos; Branner, Kim;

    2014-01-01

    , which was subject to various configurations in order to simulate different   degrees   of   damage.   Excitation   was   performed   in   two   ways:   near   the delamination zone in a simulation of operational wind excitations, and with a bar designed to excite torsional modes of the wind turbine blade.  We......Testing   was   performed   on   a   34   meter   blade   at   a   facility   in   DTU   Risø   Campus, featuring   both   wired   accelerometers   and   low­power   MEMs­based   wireless accelerometers. Testing was focused on an induced delamination area on the trailing edge of the blade...... compare the data collected from the wireless sensors against wired sensors to demonstrate their performance. We explore methods for determining damage. We first explore results of autoregressive coefficients for indicating damage levels. Finally, we demonstrate the use of damage sensitive features from the wavelet transforms of input and output signals to provide a method suitable for non­stationary blade excitations. ...

  18. Self-Locking Avoidance and Stiffness Compensation of a Three-Axis Micromachined Electrostatically Suspended Accelerometer

    Directory of Open Access Journals (Sweden)

    Yonggang Yin

    2016-05-01

    Full Text Available A micromachined electrostatically-suspended accelerometer (MESA is a kind of three-axis inertial sensor based on fully-contactless electrostatic suspension of the proof mass (PM. It has the potential to offer broad bandwidth, high sensitivity, wide dynamic range and, thus, would be perfectly suited for land seismic acquisition. Previous experiments showed that it is hard to lift up the PM successfully during initial levitation as the mass needs to be levitated simultaneously in all six degrees of freedom (DoFs. By analyzing the coupling electrostatic forces and torques between three lateral axes, it is found there exists a self-locking zone due to the cross-axis coupling effect. To minimize the cross-axis coupling and solve the initial levitation problem, this paper proposes an effective control scheme by delaying the operation of one lateral actuator. The experimental result demonstrates that the PM can be levitated up with six-DoF suspension operation at any initial position. We also propose a feed-forward compensation approach to minimize the negative stiffness effect inherent in electrostatic suspension. The experiment results demonstrate that a more broadband linear amplitude-frequency response and higher suspension stiffness can be achieved, which is crucial to maintain high vector fidelity for potential use as a three-component MEMS geophone. The preliminary performance tests of the three-axis linear accelerometer were conducted under normal atmospheric pressure and room temperature. The main results and noise analysis are presented. It is shown that vacuum packaging of the MEMS sensor is essential to extend the bandwidth and lower the noise floor, especially for low-noise seismic data acquisition.

  19. Self-Locking Avoidance and Stiffness Compensation of a Three-Axis Micromachined Electrostatically Suspended Accelerometer.

    Science.gov (United States)

    Yin, Yonggang; Sun, Boqian; Han, Fengtian

    2016-01-01

    A micromachined electrostatically-suspended accelerometer (MESA) is a kind of three-axis inertial sensor based on fully-contactless electrostatic suspension of the proof mass (PM). It has the potential to offer broad bandwidth, high sensitivity, wide dynamic range and, thus, would be perfectly suited for land seismic acquisition. Previous experiments showed that it is hard to lift up the PM successfully during initial levitation as the mass needs to be levitated simultaneously in all six degrees of freedom (DoFs). By analyzing the coupling electrostatic forces and torques between three lateral axes, it is found there exists a self-locking zone due to the cross-axis coupling effect. To minimize the cross-axis coupling and solve the initial levitation problem, this paper proposes an effective control scheme by delaying the operation of one lateral actuator. The experimental result demonstrates that the PM can be levitated up with six-DoF suspension operation at any initial position. We also propose a feed-forward compensation approach to minimize the negative stiffness effect inherent in electrostatic suspension. The experiment results demonstrate that a more broadband linear amplitude-frequency response and higher suspension stiffness can be achieved, which is crucial to maintain high vector fidelity for potential use as a three-component MEMS geophone. The preliminary performance tests of the three-axis linear accelerometer were conducted under normal atmospheric pressure and room temperature. The main results and noise analysis are presented. It is shown that vacuum packaging of the MEMS sensor is essential to extend the bandwidth and lower the noise floor, especially for low-noise seismic data acquisition. PMID:27213376

  20. Comparison of two accelerometer filter settings in individuals with Parkinson’s disease

    International Nuclear Information System (INIS)

    This study compared common free-living physical activity (PA) outcomes, assessed with the Actigraph GT3X+ accelerometer and processed with two different filter settings, in a sample of elderly individuals with Parkinson´s disease (PD). Sixty-six individuals (73.1  ±  5.8 years) with mild to moderate idiopathic PD carried an accelerometer for 7 d. Data were processed with the default filter setting and a low frequency extension filter (LFE). Significantly larger values were obtained with the LFE for mean counts and steps per day, and for minutes per day in low intensity- and lifestyle activities at moderate intensity, but not for moderate-to vigorous intensity ambulatory activities. The largest difference was observed for mean ± SD steps per day (default = 4730  ±  3210; LFE = 11 117  ±  4553). Intraclass correlation confidence intervals and limits of agreement were generally wide, indicating poor agreement. A sub-study, in which 15 individuals with PD performed a self-paced 3 min walk, demonstrated that neither filter setting differed from video-recorded steps (p ≥ 0.05). This suggests that the LFE might overestimate PA-outcomes in free-living conditions. Until new evidence supporting an extension of the lower filter-band is presented, it is recommended that the default filter setting be used when assessing PA in elderly individuals with PD. (paper)

  1. Synergistic control of forearm based on accelerometer data and artificial neural networks

    Directory of Open Access Journals (Sweden)

    B. Mijovic

    2008-05-01

    Full Text Available In the present study, we modeled a reaching task as a two-link mechanism. The upper arm and forearm motion trajectories during vertical arm movements were estimated from the measured angular accelerations with dual-axis accelerometers. A data set of reaching synergies from able-bodied individuals was used to train a radial basis function artificial neural network with upper arm/forearm tangential angular accelerations. The trained radial basis function artificial neural network for the specific movements predicted forearm motion from new upper arm trajectories with high correlation (mean, 0.9149-0.941. For all other movements, prediction was low (range, 0.0316-0.8302. Results suggest that the proposed algorithm is successful in generalization over similar motions and subjects. Such networks may be used as a high-level controller that could predict forearm kinematics from voluntary movements of the upper arm. This methodology is suitable for restoring the upper limb functions of individuals with motor disabilities of the forearm, but not of the upper arm. The developed control paradigm is applicable to upper-limb orthotic systems employing functional electrical stimulation. The proposed approach is of great significance particularly for humans with spinal cord injuries in a free-living environment. The implication of a measurement system with dual-axis accelerometers, developed for this study, is further seen in the evaluation of movement during the course of rehabilitation. For this purpose, training-related changes in synergies apparent from movement kinematics during rehabilitation would characterize the extent and the course of recovery. As such, a simple system using this methodology is of particular importance for stroke patients. The results underlie the important issue of upper-limb coordination.

  2. Assessment of the MyWellness Key accelerometer in people with type 2 diabetes.

    Science.gov (United States)

    McGinley, Samantha Kate; Armstrong, Marni J; Khandwala, Farah; Zanuso, Silvano; Sigal, Ronald J

    2015-11-01

    Accelerometers are designed to measure physical activity (PA) objectively. The MyWellness Key (MWK) accelerometer has been validated primarily in younger, normal-weight populations. The aims of this study were to examine the accuracy of the MWK against directly measured lab-based exercise and free-living PA in people with type 2 diabetes, many of whom are older and overweight or obese. Thirty-five participants with type 2 diabetes completed the protocol, which included a laboratory-based session and a free-living phase. In the laboratory visit, participants completed a structured treadmill protocol wearing MWKs on each hip (all subjects) and bra cup (women only). The speed where each MWK switched from recording light- to moderate-intensity activity was determined for each MWK worn. In the free-living phase, participants wore the MWK for all waking hours for 2 weeks, and recorded exercise in PA diaries immediately after each exercise session. The mean cut-points between low ("Free") and moderate ("Play") intensity for the right and left waist-worn MWKs were 4.1 ± 0.5 km/h and 5.0 ± 0.9 km/h for the bra-mounted MWK; ideal cut-point would be 4.0 km/h. In the free-living phase, the Spearman correlation between PA according to PA diary and the waist-worn MWK was 0.81 (95% confidence interval (CI): 0.76, 0.85; P diabetes. The MWK underestimated PA volume and intensity when worn on a bra.

  3. Accuracy of StepWatch™ and ActiGraph accelerometers for measuring steps taken among persons with multiple sclerosis.

    Directory of Open Access Journals (Sweden)

    Brian M Sandroff

    Full Text Available INTRODUCTION: There has been increased interest in the objective monitoring of free-living walking behavior using accelerometers in clinical research involving persons with multiple sclerosis (MS. The current investigation examined and compared the accuracy of the StepWatch activity monitor and ActiGraph model GT3X+ accelerometer for capturing steps taken during various speeds of prolonged, over-ground ambulation in persons with MS who had mild, moderate, and severe disability. METHODS: Sixty-three persons with MS underwent a neurological examination for generation of an EDSS score and undertook two trials of walking on the GAITRite electronic walkway. Participants were fitted with accelerometers, and undertook three modified six-minute walk (6MW tests that were interspersed with 10-15 minutes of rest. The first 6MW was undertaken at a comfortable walking speed (CWS, and the two remaining 6MW tests were undertaken above (faster walking speed; FWS or below (slower walking speed; SWS the participant's CWS. The actual number of steps taken was counted through direct observation using hand-tally counters. RESULTS: The StepWatch activity monitor (99.8%-99.9% and ActiGraph model GT3X+ accelerometer (95.6%-97.4% both demonstrated highly accurate measurement of steps taken under CWS and FWS conditions. The StepWatch had better accuracy (99.0% than the ActiGraph (95.5% in the overall sample under the SWS condition, and this was particularly apparent in those with severe disability (StepWatch: 95.7%; ActiGraph: 87.3%. The inaccuracy in measurement for the ActiGraph was associated with alterations of gait (e.g., slower gait velocity, shorter step length, wider base of support. CONCLUSIONS: This research will help inform the choice of accelerometer to be adopted in clinical trials of MS wherein the monitoring of free-living walking behavior is of particular value.

  4. Accuracy of StepWatch™ and ActiGraph Accelerometers for Measuring Steps Taken among Persons with Multiple Sclerosis

    Science.gov (United States)

    Sandroff, Brian M.; Motl, Robert W.; Pilutti, Lara A.; Learmonth, Yvonne C.; Ensari, Ipek; Dlugonski, Deirdre; Klaren, Rachel E.; Balantrapu, Swathi; Riskin, Barry J.

    2014-01-01

    Introduction There has been increased interest in the objective monitoring of free-living walking behavior using accelerometers in clinical research involving persons with multiple sclerosis (MS). The current investigation examined and compared the accuracy of the StepWatch activity monitor and ActiGraph model GT3X+ accelerometer for capturing steps taken during various speeds of prolonged, over-ground ambulation in persons with MS who had mild, moderate, and severe disability. Methods Sixty-three persons with MS underwent a neurological examination for generation of an EDSS score and undertook two trials of walking on the GAITRite electronic walkway. Participants were fitted with accelerometers, and undertook three modified six-minute walk (6MW) tests that were interspersed with 10–15 minutes of rest. The first 6MW was undertaken at a comfortable walking speed (CWS), and the two remaining 6MW tests were undertaken above (faster walking speed; FWS) or below (slower walking speed; SWS) the participant's CWS. The actual number of steps taken was counted through direct observation using hand-tally counters. Results The StepWatch activity monitor (99.8%–99.9%) and ActiGraph model GT3X+ accelerometer (95.6%–97.4%) both demonstrated highly accurate measurement of steps taken under CWS and FWS conditions. The StepWatch had better accuracy (99.0%) than the ActiGraph (95.5%) in the overall sample under the SWS condition, and this was particularly apparent in those with severe disability (StepWatch: 95.7%; ActiGraph: 87.3%). The inaccuracy in measurement for the ActiGraph was associated with alterations of gait (e.g., slower gait velocity, shorter step length, wider base of support). Conclusions This research will help inform the choice of accelerometer to be adopted in clinical trials of MS wherein the monitoring of free-living walking behavior is of particular value. PMID:24714028

  5. A novel three-component hybrid-integrated optical accelerometer based on a Mach-Zehnder interferometer with a LiNbO3 photoelastic waveguide

    Institute of Scientific and Technical Information of China (English)

    Dong-lin TANG; Xiao-dong ZHANG; Guang-hui ZHAO; Zhi-yong DAI; Xin LAI; Feng GUO

    2009-01-01

    An investigation of the properties ofa LiNbO3 photoelastic waveguide via the acceleration-induced effect is presented.A novel three-component hybrid-integrated optical accelerometer based on a Mach-Zehnder interferometer with a LiNbO3 photoelastic waveguide has been designed, which is capable of detecting seismic acceleration in high-accuracy seismic exploration.The Mach-Zehnder interferometer was successfully fabricated and a lighting test used to check its quality. The frequency response characteristic of the accelerometer was measured. The accelerometer with a resonant frequency of 3549 Hz was demonstrated to show good linear frequency responding characteristics in the range of 100-3000 Hz. The accelerometer also shows good stability and consistency. Experimental results indicate that the outputs of the on- and cross-axis are 147 and 21.3 mV, respectively.

  6. The use of a beryllium Hopkinson bar to characterize in-axis and cross-axis accelerometer response in shock environments

    Energy Technology Data Exchange (ETDEWEB)

    Bateman, V.I.; Brown, F.A.

    1997-05-01

    The characteristics of a piezoresistive accelerometer in shock environments are being studied at Sandia National Laboratories in the Mechanical Shock Testing Laboratory. A beryllium Hopkinson bar capability has been developed to extend the understanding of the piezoresistive accelerometer, in two mechanical configurations and with and without mechanical isolation, in the high frequency, high shock environments where measurements are being made. In this paper, recent measurements with beryllium single and split-Hopkinson bar configurations are described. The in axis performance of the piezoresistive accelerometer in mechanical isolation for frequencies of dc-30 kHz and shock magnitudes of up to 6,000 g as determined from measurements with a beryllium Hopkinson bar with a certified laser doppler vibrometer as the reference measurement are presented. Results of characterizations of the accelerometers subjected to cross axis shocks in a split beryllium Hopkinson bar configuration are also presented.

  7. An investigation of the orthogonal outputs from an on-rotor MEMS accelerometer for reciprocating compressor condition monitoring

    Science.gov (United States)

    Feng, G.; Hu, N.; Mones, Z.; Gu, F.; Ball, A. D.

    2016-08-01

    With rapid development in electronics and microelectromechanical systems (MEMS) technology, it becomes possible and attractive to monitor rotor dynamics by directly installing MEMS accelerometers on rotors. This paper studies the mathematical modelling of the orthogonal outputs from an on-rotor MEMS accelerometer and proposes a method to eliminate the gravitational acceleration projected on the measurement axes. This is achieved by shifting the output in the normal direction by π / 2 using a Hilbert transform and then combining it with the output of the tangential direction. With further compensation of the combined signal in the frequency domain, the tangential acceleration of the rotor is reconstructed to a high degree of accuracy. Experimental results show that the crankshaft tangential acceleration of a reciprocating compressor, obtained by the proposed method, can discriminate clearly between different discharge pressures and hence can allow common leakage faults to be detected, located and diagnosed for online condition monitoring purposes.

  8. Intelligent tires for identifying coefficient of friction of tire/road contact surfaces using three-axis accelerometer

    International Nuclear Information System (INIS)

    Intelligent tires equipped with sensors as well as the monitoring of the tire/road contact conditions are in demand for improving vehicle control and safety. With the aim of identifying the coefficient of friction of tire/road contact surfaces during driving, including during cornering, we develop an identification scheme for the coefficient of friction that involves estimation of the slip angle and applied force by using a single lightweight three-axis accelerometer attached on the inner surface of the tire. To validate the developed scheme, we conduct tire-rolling tests using an accelerometer-equipped tire with various slip angles on various types of road surfaces, including dry and wet surfaces. The results of these tests confirm that the estimated slip angle and applied force are reasonable. Furthermore, the identified coefficient of friction by the developed scheme agreed with that measured by standardized tests. (paper)

  9. Effect of the Detector Width and Gas Pressure on the Frequency Response of a Micromachined Thermal Accelerometer

    Directory of Open Access Journals (Sweden)

    Johann Courteaud

    2011-05-01

    Full Text Available In the present work, the design and the environmental conditions of a micromachined thermal accelerometer, based on convection effect, are discussed and studied in order to understand the behavior of the frequency response evolution of the sensor. It has been theoretically and experimentally studied with different detector widths, pressure and gas nature. Although this type of sensor has already been intensively examined, little information concerning the frequency response modeling is currently available and very few experimental results about the frequency response are reported in the literature. In some particular conditions, our measurements show a cut-off frequency at −3 dB greater than 200 Hz. By using simple cylindrical and planar models of the thermal accelerometer and an equivalent electrical circuit, a good agreement with the experimental results has been demonstrated.

  10. Identification of Prey Captures in Australian Fur Seals (Arctocephalus pusillus doriferus) Using Head-Mounted Accelerometers: Field Validation with Animal-Borne Video Cameras

    OpenAIRE

    Beth L. Volpov; Andrew J. Hoskins; Battaile, Brian C.; Morgane Viviant; Wheatley, Kathryn E.; Greg Marshall; Kyler Abernathy; Arnould, John P. Y.

    2015-01-01

    This study investigated prey captures in free-ranging adult female Australian fur seals (Arctocephalus pusillus doriferus) using head-mounted 3-axis accelerometers and animal-borne video cameras. Acceleration data was used to identify individual attempted prey captures (APC), and video data were used to independently verify APC and prey types. Results demonstrated that head-mounted accelerometers could detect individual APC but were unable to distinguish among prey types (fish, cephalopod, st...

  11. SPE-5 Ground-Motion Prediction at Far-Field Geophone and Accelerometer Array Sites and SPE-5 Moment and Corner-Frequency Prediction

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoning [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Patton, Howard John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chen, Ting [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-25

    This report offers predictions for the SPE-5 ground-motion and accelerometer array sites. These predictions pertain to the waveform and spectral amplitude at certain geophone sites using Denny&Johnson source model and a source model derived from SPE data; waveform, peak velocity and peak acceleration at accelerometer sites using the SPE source model and the finite-difference simulation with LLNL 3D velocity model; and the SPE-5 moment and corner frequency.

  12. Identification of the occurrence and pattern of masseter muscle activities during sleep using EMG and accelerometer systems

    OpenAIRE

    Sato Sadao; Tamaki Katsushi; Sasaguri Kenichi; Yoshimi Hidehiro

    2009-01-01

    Abstract Background Sleep bruxism has been described as a combination of different orofacial motor activities that include grinding, clenching and tapping, although accurate distribution of the activities still remains to be clarified. Methods We developed a new system for analyzing sleep bruxism to examine the muscle activities and mandibular movement patterns during sleep bruxism. The system consisted of a 2-axis accelerometer, electroencephalography and electromyography. Nineteen healthy v...

  13. Validity of Using Tri-Axial Accelerometers to Measure Human Movement - Part I: Posture and Movement Detection

    OpenAIRE

    Lugade, Vipul; Fortune, Emma; Morrow, Melissa; Kaufman, Kenton

    2013-01-01

    A robust method for identifying movement in the free-living environment is needed to objectively measure physical activity. The purpose of this study was to validate the identification of postural orientation and movement from acceleration data against visual inspection from video recordings. Using tri-axial accelerometers placed on the waist and thigh, static orientations of standing, sitting, and lying down, as well as dynamic movements of walking, jogging and transitions between postures w...

  14. Association between toe grasping strength and accelerometer-determined physical activity in middle-aged and older women

    OpenAIRE

    Abe, Takashi; Thiebaud, Robert S.; Loenneke, Jeremy P.; Mitsukawa, Naotoshi

    2015-01-01

    [Purpose] To test the hypothesis that toe grasping strength is associated with daily physical activity in older adults. [Subjects] Fifty-seven Japanese women, aged 52–78 years, volunteered. [Methods] Toe grasping and knee extension strength were measured. Physical activity was also measured, using an accelerometer, and the total duration of each level of exercise intensity (light, moderate, and vigorous) and average step counts were calculated. Subjects were separated into two groups on the b...

  15. VLC-Based Positioning System for an Indoor Environment Using an Image Sensor and an Accelerometer Sensor

    OpenAIRE

    Huynh, Phat; Yoo, Myungsik

    2016-01-01

    Recently, it is believed that lighting and communication technologies are being replaced by high power LEDs, which are core parts of the visible light communication (VLC) system. In this paper, by taking advantages of VLC, we propose a novel design for an indoor positioning system using LEDs, an image sensor (IS) and an accelerometer sensor (AS) from mobile devices. The proposed algorithm, which provides a high precision indoor position, consists of four LEDs mounted on the ceiling transmitti...

  16. Implementation of a smartphone wireless accelerometer platform for establishing deep brain stimulation treatment efficacy of essential tremor with machine learning.

    Science.gov (United States)

    LeMoyne, Robert; Tomycz, Nestor; Mastroianni, Timothy; McCandless, Cyrus; Cozza, Michael; Peduto, David

    2015-01-01

    Essential tremor (ET) is a highly prevalent movement disorder. Patients with ET exhibit a complex progressive and disabling tremor, and medical management often fails. Deep brain stimulation (DBS) has been successfully applied to this disorder, however there has been no quantifiable way to measure tremor severity or treatment efficacy in this patient population. The quantified amelioration of kinetic tremor via DBS is herein demonstrated through the application of a smartphone (iPhone) as a wireless accelerometer platform. The recorded acceleration signal can be obtained at a setting of the subject's convenience and conveyed by wireless transmission through the Internet for post-processing anywhere in the world. Further post-processing of the acceleration signal can be classified through a machine learning application, such as the support vector machine. Preliminary application of deep brain stimulation with a smartphone for acquisition of a feature set and machine learning for classification has been successfully applied. The support vector machine achieved 100% classification between deep brain stimulation in `on' and `off' mode based on the recording of an accelerometer signal through a smartphone as a wireless accelerometer platform.

  17. Validity of using tri-axial accelerometers to measure human movement - Part I: Posture and movement detection.

    Science.gov (United States)

    Lugade, Vipul; Fortune, Emma; Morrow, Melissa; Kaufman, Kenton

    2014-02-01

    A robust method for identifying movement in the free-living environment is needed to objectively measure physical activity. The purpose of this study was to validate the identification of postural orientation and movement from acceleration data against visual inspection from video recordings. Using tri-axial accelerometers placed on the waist and thigh, static orientations of standing, sitting, and lying down, as well as dynamic movements of walking, jogging and transitions between postures were identified. Additionally, subjects walked and jogged at self-selected slow, comfortable, and fast speeds. Identification of tasks was performed using a combination of the signal magnitude area, continuous wavelet transforms and accelerometer orientations. Twelve healthy adults were studied in the laboratory, with two investigators identifying tasks during each second of video observation. The intraclass correlation coefficients for inter-rater reliability were greater than 0.95 for all activities except for transitions. Results demonstrated high validity, with sensitivity and positive predictive values of greater than 85% for sitting and lying, with walking and jogging identified at greater than 90%. The greatest disagreement in identification accuracy between the algorithm and video occurred when subjects were asked to fidget while standing or sitting. During variable speed tasks, gait was correctly identified for speeds between 0.1m/s and 4.8m/s. This study included a range of walking speeds and natural movements such as fidgeting during static postures, demonstrating that accelerometer data can be used to identify orientation and movement among the general population.

  18. A method for extracting human gait series from accelerometer signals based on the ensemble empirical mode decomposition

    Science.gov (United States)

    Fu, Mao-Jing; Zhuang, Jian-Jun; Hou, Feng-Zhen; Zhan, Qing-Bo; Shao, Yi; Ning, Xin-Bao

    2010-05-01

    In this paper, the ensemble empirical mode decomposition (EEMD) is applied to analyse accelerometer signals collected during normal human walking. First, the self-adaptive feature of EEMD is utilised to decompose the accelerometer signals, thus sifting out several intrinsic mode functions (IMFs) at disparate scales. Then, gait series can be extracted through peak detection from the eigen IMF that best represents gait rhythmicity. Compared with the method based on the empirical mode decomposition (EMD), the EEMD-based method has the following advantages: it remarkably improves the detection rate of peak values hidden in the original accelerometer signal, even when the signal is severely contaminated by the intermittent noises; this method effectively prevents the phenomenon of mode mixing found in the process of EMD. And a reasonable selection of parameters for the stop-filtering criteria can improve the calculation speed of the EEMD-based method. Meanwhile, the endpoint effect can be suppressed by using the auto regressive and moving average model to extend a short-time series in dual directions. The results suggest that EEMD is a powerful tool for extraction of gait rhythmicity and it also provides valuable clues for extracting eigen rhythm of other physiological signals.

  19. A wide-range micromachined threshold accelerometer array and interface circuit

    Science.gov (United States)

    Selvakumar, Arjun; Yazdi, Navid; Najafi, Khalil

    2001-03-01

    This paper presents a complete threshold acceleration detection microsystem comprising an array of threshold accelerometers and a low power interface circuit. The sensors were designed and fabricated using the bulk-silicon dissolved-wafer process. The process offers a wide latitude in sensor threshold levels, as demonstrated in the fabrication of devices with levels of 1.5-1000 g, bandwidths of 45 Hz to 40 kHz, with mass sizes ranging from 0.015 µg to 0.7 µg, and low-resistance gold-gold contacts for the switch. The interface circuit dissipates less than 300 µW, measures 2.2 mm×2.2 mm it was fabricated in-house using a standard 3 µm, p-well CMOS (complementary metal oxide semiconductor) process, and is connected to the sensor chip in a multi-chip module. The key aspects of the microsystem are the implementation of sensor redundancy and supporting circuit logic to improve detection accuracy and fault tolerance, which are crucial factors in many applications. In addition, the microsystem supports communication with a standard microcontroller bus in a smart sensor network.

  20. Properties of traveling atmospheric disturbances (TADs) inferred from CHAMP accelerometer observations

    Science.gov (United States)

    Bruinsma, Sean L.; Forbes, Jeffrey M.

    2009-02-01

    Densities derived from accelerometer measurements on the CHAMP satellite near 400 km are used to statistically establish characteristics of large-scale (>1000 km) traveling atmospheric disturbances (TADs). Only TADs that at least propagate from the auroral zone to the equator are analyzed here, and a total of 21 identifiable events are found over the years 2001 2007. The average speed of all TADs, regardless of local time, is 646 ± 122 ms-1. The average speeds on the dayside and nightside are 595 ± 127 ms-1 and 685 ± 106 ms-1, respectively, i.e., the speed appears to be 10% higher on average on the nightside. On six occasions TADs were only detected on the night side; however, TADs on the dayside often appear more distinctly in the data. Moreover, contrary to some theoretical expectations, dayside TADs do not dissipate more readily than night side TADs, although much less are detected between 8 20 solar local time. No clear dependence of TAD amplitude or phase speed with respect to Kp, or rate of increase of Kp, is found.

  1. Optimization of an Accelerometer and Gyroscope-Based Fall Detection Algorithm

    Directory of Open Access Journals (Sweden)

    Quoc T. Huynh

    2015-01-01

    Full Text Available Falling is a common and significant cause of injury in elderly adults (>65 yrs old, often leading to disability and death. In the USA, one in three of the elderly suffers from fall injuries annually. This study’s purpose is to develop, optimize, and assess the efficacy of a falls detection algorithm based upon a wireless, wearable sensor system (WSS comprised of a 3-axis accelerometer and gyroscope. For this study, the WSS is placed at the chest center to collect real-time motion data of various simulated daily activities (i.e., walking, running, stepping, and falling. Tests were conducted on 36 human subjects with a total of 702 different movements collected in a laboratory setting. Half of the dataset was used for development of the fall detection algorithm including investigations of critical sensor thresholds and the remaining dataset was used for assessment of algorithm sensitivity and specificity. Experimental results show that the algorithm detects falls compared to other daily movements with a sensitivity and specificity of 96.3% and 96.2%, respectively. The addition of gyroscope information enhances sensitivity dramatically from results in the literature as angular velocity changes provide further delineation of a fall event from other activities that may also experience high acceleration peaks.

  2. Design and process test of a novel MOEMS accelerometer based on Raman-Nath diffraction

    Institute of Scientific and Technical Information of China (English)

    Zhang Zuwei; Wen Zhiyu; Shang Zhengguo; Li Dongling; Hu Jing

    2012-01-01

    A novel micro-opto-electro-mechanical system (MOEMS) accelerometer based on Raman-Nath diffraction is presented.It mainly consists of an FPW delay line oscillator and optical strip waveguides.The fundamental theories and principles of the device are introduced briefly.A flexural plate-wave delay-line oscillator is designed to work as an acousto-optic (AO) shifter,which has a Klein-Cook parameter of 0.38.Single-mode optical strip waveguides of 2 μm in width and thicknesses of 0.6 μm are designed by using the effective index method for light transmission.The E0y0 mode waveguide polarizers are designed to ensure the consistency of the light polarization in the waveguides.The fabrication process,based on (100) oriented,450-μm-thick silicon wafers is proposed in detail,and some difficulties in the process are discussed carefully.At last,a series of process tests are undertaken to solve the proposed problems.The results indicate that the proposed design and fabrication process of the device is dependable and realizable.

  3. Wireless accelerometer network for process monitoring during mold forming in lost foam casting

    Science.gov (United States)

    Whelan, Matthew J.; Janoyan, Kerop D.

    2006-03-01

    Lost Foam Casting (LFC) enables the production of complex castings while offering the advantages of consolidation of components, reduced machining, and recirculation of the casting mold material. In the process, a replica of the desired product is produced of blown polystyrene, coated in refractory slurry, and cast in a dense, unbonded sand mold. In order for the unbonded sand mold to fill into pattern holes and to provide sufficient confining force to prevent the advancing molten front from penetrating beyond the mold boundaries, the sand mold is produced by an overhead raining and flask vibration schedule that encourages fluidization and subsequent densification. The amplitude, frequency, and duration of the flask vibration as well as the rate of sand filling are critical parameters in achieving quality castings. Currently, many foundries use an often-lengthy trial-and-error process for determining an acceptable raining and vibration schedule for each specific mold and rely heavily on simple measurements and operator experience to control the mold making process on the foundry line. This study focuses on developing a wireless sensor network of accelerometers to monitor vibrational characteristics of the casting flask during the mold making stage of LFC. Transformations in the vibrational characteristics of the flask can provide a "signature" for indicating the condition of the unbonded sand mold. Additionally, the wireless nature of the sensor nodes enables the technology to travel across the foundry floor during the casting cycle eliminating the necessity of routine placement and setup.

  4. Recognizing Human Activities User-independently on Smartphones Based on Accelerometer Data

    Directory of Open Access Journals (Sweden)

    Pekka Siirtola

    2012-06-01

    Full Text Available Real-time human activity recognition on a mobile phone is presented in this article. Unlike in most other studies, not only the data were collected using the accelerometers of a smartphone, but also models were implemented to the phone and the whole classification process (preprocessing, feature extraction and classification was done on the device. The system is trained using phone orientation independent features to recognize five everyday activities: walking, running, cycling, driving a car and sitting/standing while the phone is in the pocket of the subject's trousers. Two classifiers were compared, knn (k nearest neighbors and QDA (quadratic discriminant analysis. The models for real-time activity recognition were trained offline using a data set collected from eight subjects and these offline results were compared to real-time recognition rates, which are obtained by implementing models to mobile activity recognition application which currently supports two operating systems: Symbian^3 and Android. The results show that the presented method is light and, therefore, suitable for be used in real-time recognition. In addition, the recognition rates on the smartphones were encouraging, in fact, the recognition accuracies obtained are approximately as high as offline recognition rates. Also, the results show that the method presented is not an operating system dependent.

  5. A novel sandwich differential capacitive accelerometer with symmetrical double-sided serpentine beam-mass structure

    International Nuclear Information System (INIS)

    This paper presents a novel differential capacitive silicon micro-accelerometer with symmetrical double-sided serpentine beam-mass sensing structure and glass–silicon–glass sandwich structure. The symmetrical double-sided serpentine beam-mass sensing structure is fabricated with a novel pre-buried mask fabrication technology, which is convenient for manufacturing multi-layer sensors. The glass–silicon–glass sandwich structure is realized by a double anodic bonding process. To solve the problem of the difficulty of leading out signals from the top and bottom layer simultaneously in the sandwich sensors, a silicon pillar structure is designed that is inherently simple and low-cost. The prototype is fabricated and tested. It has low noise performance (the peak to peak value is 40 μg) and μg-level Allan deviation of bias (2.2 μg in 1 h), experimentally demonstrating the effectiveness of the design and the novel fabrication technology. (paper)

  6. Design and application of single-antenna GPS/accelerometers attitude determination system

    Institute of Scientific and Technical Information of China (English)

    He Jie; Huang Xianlin; Wang Guofeng

    2008-01-01

    In view of the problem that the current single-antenna GPS attitude determination system can only determine the body attitude when the sideslip angle is zero and the multiantenna GPS/SINS integrated navigation system is of large volume, high cost, and complex structure, this approach is presented to determine the attitude based on vector space with single-antenna GPS and accelerometers in the micro inertial measurement unit (MIMU).It can provide real-time and accurate attitude information. Subsequently, the single-antenna GPS/SINS integrated navigation system is designed based on the combination of position, velocity, and attitude. Finally the semi-physical simulations of single-antenna GPS attitude determination system and single-antenna GPS/SINS integrated navigation system are carried out. The simulation results, based on measured data, show that the single-antenna GPS/SINS system can provide more accurate navigation information compared to the GPS/SINS system, based on the combination of position and velocity. Furthermore, the single-antenna GPS/SINS system is characteristic of lower cost and simpler structure. It provides the basis for the application of a single-antenna GPS/SINS integrated navigation system in a micro aerial vehicle (MAV).

  7. An Accelerometer Based Instrumentation of the Golf Club: Comparative Analysis of Golf Swings

    CERN Document Server

    Grober, Robert D

    2010-01-01

    The motion of the golf club is measured using two accelerometers mounted at different points along the shaft of the golf club, both sensitive to acceleration along the axis of the shaft. The resulting signals are resolved into differential and common mode components. The differential mode, a measure of the centripetal acceleration of the golf club, is a reasonable proxy for club speed and can be used to understand details of tempo, rhythm, and timing. The common mode, related to the acceleration of the hands, allows insight into the torques that generate speed in the golf swing. This measurement scheme is used in a comparative study of twenty-five golfers in which it is shown that club head speed is generated in the downswing as a two step process. The first phase involves impulsive acceleration of the hands and club. This is followed by a second phase where the club is accelerated while the hands decelerate. This study serves to emphasize that the measurement scheme yields a robust data set which provides de...

  8. Improved rapid magnitude estimation for a community-based, low-cost MEMS accelerometer network

    Science.gov (United States)

    Chung, Angela I.; Cochran, Elizabeth S.; Kaiser, Anna E.; Christensen, Carl M.; Yildirim, Battalgazi; Lawrence, Jesse F.

    2015-01-01

    Immediately following the Mw 7.2 Darfield, New Zealand, earthquake, over 180 Quake‐Catcher Network (QCN) low‐cost micro‐electro‐mechanical systems accelerometers were deployed in the Canterbury region. Using data recorded by this dense network from 2010 to 2013, we significantly improved the QCN rapid magnitude estimation relationship. The previous scaling relationship (Lawrence et al., 2014) did not accurately estimate the magnitudes of nearby (estimates earthquake magnitudes within 1 magnitude unit of the GNS Science GeoNet earthquake catalog magnitudes for 99% of the events tested, within 0.5 magnitude units for 90% of the events, and within 0.25 magnitude units for 57% of the events. These magnitudes are reliably estimated within 3 s of the initial trigger recorded on at least seven stations. In this report, we present the methods used to calculate a new scaling relationship and demonstrate the accuracy of the revised magnitude estimates using a program that is able to retrospectively estimate event magnitudes using archived data.

  9. Development of a Microcontroller-based Wireless Accelerometer for Kinematic Analysis

    Directory of Open Access Journals (Sweden)

    Maria Clarissa Alvarez Carasco

    2015-06-01

    Full Text Available Wireless sensor networks (WSNs allow real-time measurement and monitoring with less complexity and more efficient in terms of obtaining data when the subject is in motion. It eliminates the limitations introduced by wired connections between the sensors and the central processing unit. Although wireless technology is widely used around the world, not much has been applied for education. Through VISSER, a low cost WSN using nRF24L01+ RF transceiver that is developed to observe and analyze the kinematics of a moving object is discussed in this paper. Data acquisition and transmission is realized with the use of a low power and low cost microcontroller ATtiny85 that obtains data from the ADXL345 three-axis accelerometer. An ATtiny85 also controls the receiving module with a UART connection to the computer. Data gathered are then processed in an open-source programming language to determine properties of an object’s motion such as pitch and roll (tilt, acceleration and displacement. This paper discusses the application of the developed WSN for the kinematics analysis of a toy car moving on flat and inclined surfaces along the three axes. The developed system can be used in various motion detection and other kinematics applications, as well as physics laboratory activities for educational purposes.

  10. Sleep Monitoring Based on a Tri-Axial Accelerometer and a Pressure Sensor

    Science.gov (United States)

    Nam, Yunyoung; Kim, Yeesock; Lee, Jinseok

    2016-01-01

    Sleep disorders are a common affliction for many people even though sleep is one of the most important factors in maintaining good physiological and emotional health. Numerous researchers have proposed various approaches to monitor sleep, such as polysomnography and actigraphy. However, such approaches are costly and often require overnight treatment in clinics. With this in mind, the research presented here has emerged from the question: “Can data be easily collected and analyzed without causing discomfort to patients?” Therefore, the aim of this study is to provide a novel monitoring system for quantifying sleep quality. The data acquisition system is equipped with multimodal sensors, including a three-axis accelerometer and a pressure sensor. To identify sleep quality based on measured data, a novel algorithm, which uses numerous physiological parameters, was proposed. Such parameters include non-REM sleep time, the number of apneic episodes, and sleep durations for dominant poses. To assess the effectiveness of the proposed system, three participants were enrolled in this experimental study for a duration of 20 days. From the experimental results, it can be seen that the proposed monitoring system is effective for quantifying sleep quality. PMID:27223290

  11. The "Fit but Fat" paradigm addressed using accelerometer-determined physical activity data

    Directory of Open Access Journals (Sweden)

    Paul Loprinzi

    2014-01-01

    Full Text Available Background: No studies have addressed the "fit but fat" paradigm using accelerometry data. Aim: The study was to determine if 1 higher levels of accelerometer-determined physical activity are favorably associated with biomarkers in overweight or obese persons (objective 1; and 2 overweight or obese individuals who are sufficiently active have better or similar biomarker levels than normal weight persons who are not sufficiently active (objective 2. Materials and Methods: Data from the 2003-2006 National Health and Nutrition Examination Survey were analyzed and included 5,146 participants aged 20-85 years. Results: Regarding objective 1, obese active individuals had more favorable waist circumference, C-reactive protein, white blood cells, and neutrophil levels when compared to obese inactive individuals; similar results were found for overweight adults. Regarding objective 2, there were no significant differences between normal weight inactive individuals and overweight active individuals for nearly all biomarkers. Similarly, there were no significant differences between normal weight inactive individuals and obese active individuals for white blood cells, neutrophils, low-density lipoprotein cholesterol, total cholesterol, triglycerides, glucose, or homocysteine. Conclusions: Physical activity has a protective effect on biomarkers in normal, overweight, and obese individuals, and overweight (not obese active individuals have a similar cardiovascular profile than normal weight inactive individuals.

  12. Estimation of upper-limb orientation based on accelerometer and gyroscope measurements.

    Science.gov (United States)

    Hyde, Rick A; Ketteringham, Laurence P; Neild, Simon A; Jones, Rosie S

    2008-02-01

    A solution is proposed to the estimation of upper-limb orientation using miniature accelerometers and gyroscopes. This type of measurement device has many different possible applications, ranging from clinical use with patients presenting a number of conditions such as upper motor neuron syndrome and pathologies that give rise to loss of dexterity, to competitive sports training and virtual reality. Here we focus on a design that minimizes the number of sensors whilst delivering estimates of known accuracy over a defined frequency range. Minimizing the sensor count can make the measurement system less obtrusive, as well as minimising cost and reducing the required bandwidth if using a wireless solution. Accurate measurement of movement amplitude up to 15 Hz is required in our immediate application, namely to quantify tremor in multiple sclerosis patients. The drive for low numbers of sensors and good accuracy at higher frequencies leads to a novel design based on composite filters. The simple estimator structure also gives good insight into the fundamental accuracy limitations based on the sensors chosen. This paper defines the underlying mathematics, and quantifies performance for an estimator for shoulder, upper arm, lower arm and hand orientations. Good estimation accuracy up to 15 Hz is indicated, and this with a reduced total sensor count of 18 compared to 24 that would be required for more conventional estimator architectures. PMID:18270013

  13. Use of a gyroscope/accelerometer data logger to identify alternative feeding behaviours in fish.

    Science.gov (United States)

    Kawabata, Yuuki; Noda, Takuji; Nakashima, Yuuki; Nanami, Atsushi; Sato, Taku; Takebe, Takayuki; Mitamura, Hiromichi; Arai, Nobuaki; Yamaguchi, Tomofumi; Soyano, Kiyoshi

    2014-09-15

    We examined whether we could identify the feeding behaviours of the trophic generalist fish Epinephelus ongus on different prey types (crabs and fish) using a data logger that incorporated a three-axis gyroscope and a three-axis accelerometer. Feeding behaviours and other burst behaviours, including escape responses, intraspecific interactions and routine movements, were recorded from six E. ongus individuals using data loggers sampling at 200 Hz, and were validated by simultaneously recorded video images. For each data-logger record, we extracted 5 s of data when any of the three-axis accelerations exceeded absolute 2.0 g, to capture all feeding behaviours and other burst behaviours. Each feeding behaviour was then identified using a combination of parameters that were derived from the extracted data. Using decision trees with the parameters, high true identification rates (87.5% for both feeding behaviours) with low false identification rates (5% for crab-eating and 6.3% for fish-eating) were achieved for both feeding behaviours.

  14. Gait feature extraction in Parkinson's disease using low-cost accelerometers.

    Science.gov (United States)

    Stamatakis, Julien; Crémers, Julien; Maquet, Didier; Macq, Benoit; Garraux, Gaëtan

    2011-01-01

    The clinical hallmarks of Parkinson's disease (PD) are movement poverty and slowness (i.e. bradykinesia), muscle rigidity, limb tremor or gait disturbances. Parkinson's gait includes slowness, shuffling, short steps, freezing of gait (FoG) and/or asymmetries in gait. There are currently no validated clinical instruments or device that allow a full characterization of gait disturbances in PD. As a step towards this goal, a four accelerometer-based system is proposed to increase the number of parameters that can be extracted to characterize parkinsonian gait disturbances such as FoG or gait asymmetries. After developing the hardware, an algorithm has been developed, that automatically epoched the signals on a stride-by-stride basis and quantified, among others, the gait velocity, the stride time, the stance and swing phases, the single and double support phases or the maximum acceleration at toe-off, as validated by visual inspection of video recordings during the task. The results obtained in a PD patient and a healthy volunteer are presented. The FoG detection will be improved using time-frequency analysis and the system is about to be validated with a state-of-the-art 3D movement analysis system.

  15. System level simulation of a micro resonant accelerometer with geometric nonlinear beams

    International Nuclear Information System (INIS)

    Geometric nonlinear behaviors of micro resonators have attracted extensive attention of MEMS (micro-electro-mechanical systems) researchers, and MEMS transducers utilizing these behaviors have been widely researched and used due to the advantages of essentially digital output. Currently, the design of transducers with nonlinear behaviors is mainly performed by numerical method and rarely by system level design method. In this paper, the geometric nonlinear beam structure was modeled and established as a reusable library component by system level modeling and simulation method MuPEN (multi port element network). A resonant accelerometer was constructed and simulated using this model together with MuPEN reusable library. The AC (alternating current) analysis results of MuPEN model agreed well with the results of architect model and the experiment results shown in the existing reference. Therefore, we are convinced that the beam component based on MuPEN method is valid, and MEMS system level design method and related libraries can effectively model and simulate transducers with geometric nonlinear behaviors if appropriate system level components are available. (paper)

  16. Reliability of Accelerometer Scores for Measuring Sedentary and Physical Activity Behaviors in Persons With Multiple Sclerosis.

    Science.gov (United States)

    Klaren, Rachel E; Hubbard, Elizabeth A; Zhu, Weimo; Motl, Robert W

    2016-04-01

    This brief research note examined the reliability of scores from an accelerometer as measures of sedentary and physical activity behaviors in persons with multiple sclerosis (MS). The analysis was performed on a combined data set from 2 previous longitudinal investigations of physical activity in MS. We focused on the number of days required to reliably estimate sedentary behavior, based on time spent in sedentary behavior per day and number of sedentary breaks, number of long sedentary bouts, and average length of sedentary bouts per day. We further examined the number of days required to reliably estimate physical activity behavior, based on time spent in light and moderate-to-vigorous physical activity and average length of activity bouts per day. Between 4-6 days of monitoring and 3-7 days of monitoring were necessary for good reliability of scores from all sedentary outcomes and physical activity outcomes, respectively. These results should guide research and practice examining sedentary and physical activity behaviors using accelerometry in persons with MS. PMID:27078272

  17. Measurement of International Roughness Index by Using Z-Axis Accelerometers and GPS

    Directory of Open Access Journals (Sweden)

    Yuchuan Du

    2014-01-01

    Full Text Available The International Roughness Index (IRI is a well-recognized standard in the field of pavement management. Many different types of devices can be used to measure the IRI, but these devices are mainly mounted on a full-size automobile and are complicated to operate. In addition, these devices are expensive. The development of methods for IRI measurement is a prerequisite for pavement management systems and other parts of the road management industry. Based on the quarter-car model and the vehicle vibration caused by road roughness, there is a strong correlation between the in-car Z-axis acceleration and the IRI. The variation of speed of the car during the measurement process has a large influence on IRI estimation. A measurement system equipped with Z-axis accelerometers and a GPS device was developed. Using the self-designing measurement system based on the methodology proposed in this study, we performed a small-scale field test. We used a one-wheel linear model and two-wheel model to fit the variation of the Z-axis acceleration. The test results demonstrated that the low-cost measurement system has good accuracy and could enhance the efficiency of IRI measurement.

  18. Accelerometer based solution for precision livestock farming: geolocation enhancement and animal activity identification

    Science.gov (United States)

    Terrasson, G.; Llaria, A.; Marra, A.; Voaden, S.

    2016-07-01

    The rapid evolution of electronics and communication technologies in the last years has contributed to the expansion of Precision Livestock Farming applications. In this context, animal geolocation systems applied to extensive farming are interesting for farmers to optimize their daily work organization. Nevertheless, the deployment of these solutions implies several technical challenges which must be resolved, mainly the energy consumption and the suitability of the communication protocols. A recently developed solution that deals with these technical challenges is the e-Pasto platform, which is composed of low power geolocation devices embedded into collars that offer an energetic autonomy of at least seven months, completed with a visualization user interface. The autonomy is assured employing a duty-cycle operation that results in one geolocation position measurement per hour. This work studies the employ of accelerometers to overcome this limitation assuring, at the same time, the required autonomy for the geolocation device. The authors also propose an algorithm that processes the acceleration data in order to identify the steps of an individual. The whole solution (step identification and geolocation) has been validated by means of several experimental tests.

  19. Sleep Monitoring Based on a Tri-Axial Accelerometer and a Pressure Sensor.

    Science.gov (United States)

    Nam, Yunyoung; Kim, Yeesock; Lee, Jinseok

    2016-05-23

    Sleep disorders are a common affliction for many people even though sleep is one of the most important factors in maintaining good physiological and emotional health. Numerous researchers have proposed various approaches to monitor sleep, such as polysomnography and actigraphy. However, such approaches are costly and often require overnight treatment in clinics. With this in mind, the research presented here has emerged from the question: "Can data be easily collected and analyzed without causing discomfort to patients?" Therefore, the aim of this study is to provide a novel monitoring system for quantifying sleep quality. The data acquisition system is equipped with multimodal sensors, including a three-axis accelerometer and a pressure sensor. To identify sleep quality based on measured data, a novel algorithm, which uses numerous physiological parameters, was proposed. Such parameters include non-REM sleep time, the number of apneic episodes, and sleep durations for dominant poses. To assess the effectiveness of the proposed system, three participants were enrolled in this experimental study for a duration of 20 days. From the experimental results, it can be seen that the proposed monitoring system is effective for quantifying sleep quality.

  20. An in-plane low-noise accelerometer fabricated with an improved process flow

    Institute of Scientific and Technical Information of China (English)

    Xu-dong ZHENG; Zhong-he JIN; Yue-lin WANG; Wei-jun LIN; Xiao-qi ZHOU

    2009-01-01

    We present a bulk micromachined in-plane capacitive accelerometer fabricated with an improved process flow, by etching only one-fifth of the wafer thickness at the back of the silicon while forming the bar-structure electrode for the sensing capacitor. The improved flow greatly lowers the footing effect during deep reactive ion etching (DRIE), and increases the proof mass by 54% compared to the traditional way, resulting in both improved device quality and a higher yield rate. Acceleration in the X direction is sensed capacitively by varying the overlapped area of a differential capacitor pair, which eliminates the nonlinear behavior by fixing the parallel-plate gap. The damping coefficient of the sensing motion is low due to the slide-film damping. A large proof mass is made using DRIE, which also ensures that dimensions of the spring beams in the Y and Z directions can be made large to lower cross axis coupling and increase the pull-in voltage. The theoretical Brownian noise floor is 0.47 μg/Hz1/2 at room temperature and atmospheric pressure. The tested frequency response of a prototype complies with the low damping design scheme. Output data for input acceleration from-1 g to 1 g are recorded by a digital multimeter and show very good linearity. The tested random bias of the prototype is 130 μg at an averaging time of around 6 s.

  1. A novel sandwich differential capacitive accelerometer with symmetrical double-sided serpentine beam-mass structure

    Science.gov (United States)

    Xiao, D. B.; Li, Q. S.; Hou, Z. Q.; Wang, X. H.; Chen, Z. H.; Xia, D. W.; Wu, X. Z.

    2016-02-01

    This paper presents a novel differential capacitive silicon micro-accelerometer with symmetrical double-sided serpentine beam-mass sensing structure and glass-silicon-glass sandwich structure. The symmetrical double-sided serpentine beam-mass sensing structure is fabricated with a novel pre-buried mask fabrication technology, which is convenient for manufacturing multi-layer sensors. The glass-silicon-glass sandwich structure is realized by a double anodic bonding process. To solve the problem of the difficulty of leading out signals from the top and bottom layer simultaneously in the sandwich sensors, a silicon pillar structure is designed that is inherently simple and low-cost. The prototype is fabricated and tested. It has low noise performance (the peak to peak value is 40 μg) and μg-level Allan deviation of bias (2.2 μg in 1 h), experimentally demonstrating the effectiveness of the design and the novel fabrication technology.

  2. Ambulatory estimation of knee-joint kinematics in anatomical coordinate system using accelerometers and magnetometers.

    Science.gov (United States)

    Kun, Liu; Inoue, Yoshio; Shibata, Kyoko; Enguo, Cao

    2011-02-01

    Knee-joint kinematics analysis using an optimal sensor set and a reliable algorithm would be useful in the gait analysis. An original approach for ambulatory estimation of knee-joint angles in anatomical coordinate system is presented, which is composed of a physical-sensor-difference-based algorithm and virtual-sensor-difference-based algorithm. To test the approach, a wearable monitoring system composed of accelerometers and magnetometers was developed and evaluated on lower limb. The flexion/extension (f/e), abduction/adduction (a/a), and inversion/extension (i/e) rotation angles of the knee joint in the anatomical joint coordinate system were estimated. In this method, since there is no integration of angular acceleration or angular velocity, the result is not distorted by offset and drift. The three knee-joint angles within the anatomical coordinate system are independent of the orders, which must be considered when Euler angles are used. Besides, since there are no physical sensors implanted in the knee joint based on the virtual-sensor-difference-based algorithm, it is feasible to analyze knee-joint kinematics with less numbers and types of sensors than those mentioned in some others methods. Compared with results from the reference system, the developed wearable sensor system is available to do gait analysis with fewer sensors and high degree of accuracy.

  3. Towards Uniform Accelerometry Analysis: A Standardization Methodology to Minimize Measurement Bias Due to Systematic Accelerometer Wear-Time Variation

    Directory of Open Access Journals (Sweden)

    Tarun R. Katapally, Nazeem Muhajarine

    2014-06-01

    Full Text Available Accelerometers are predominantly used to objectively measure the entire range of activity intensities – sedentary behaviour (SED, light physical activity (LPA and moderate to vigorous physical activity (MVPA. However, studies consistently report results without accounting for systematic accelerometer wear-time variation (within and between participants, jeopardizing the validity of these results. This study describes the development of a standardization methodology to understand and minimize measurement bias due to wear-time variation. Accelerometry is generally conducted over seven consecutive days, with participants' data being commonly considered 'valid' only if wear-time is at least 10 hours/day. However, even within ‘valid’ data, there could be systematic wear-time variation. To explore this variation, accelerometer data of Smart Cities, Healthy Kids study (www.smartcitieshealthykids.com were analyzed descriptively and with repeated measures multivariate analysis of variance (MANOVA. Subsequently, a standardization method was developed, where case-specific observed wear-time is controlled to an analyst specified time period. Next, case-specific accelerometer data are interpolated to this controlled wear-time to produce standardized variables. To understand discrepancies owing to wear-time variation, all analyses were conducted pre- and post-standardization. Descriptive analyses revealed systematic wear-time variation, both between and within participants. Pre- and post-standardized descriptive analyses of SED, LPA and MVPA revealed a persistent and often significant trend of wear-time’s influence on activity. SED was consistently higher on weekdays before standardization; however, this trend was reversed post-standardization. Even though MVPA was significantly higher on weekdays both pre- and post-standardization, the magnitude of this difference decreased post-standardization. Multivariable analyses with standardized SED, LPA and

  4. Instrumentation by accelerometers and distributed optical fiber sensors of a real ballastless track structure

    Science.gov (United States)

    Chapeleau, Xavier; Cottineau, Louis-Marie; Sedran, Thierry; Cailliau, Joël; Gueguen, Ivan; Dumoulin, Jean

    2015-04-01

    While relatively expensive to build, ballastless track structures are presently seen as an attractive alternative to conventional ballast. Firstly, they are built quickly since the slabs can be cast in place in an automated fashion by a slipform paver. Secondly, with its service life of at least 60 years, they requires little maintenance and hence they offers great availability. Other reasons for using ballastless tracks instead of ballasted tracks are the lack of suitable ballast material and the need of less noise and vibration for high-speed, in particularly. In the framework of a FUI project (n° 072906053), a new ballastless track structure based on concrete slabs was designed and its thermal-mechanical behavior in fatigue under selected mechanical and thermal conditions was tested on a real scale mockup in our laboratory [1,2]. By applying to the slabs both together mechanical stresses and thermal gradients, finite elements simulation and experimental results show that the weather conditions influence significantly the concrete slabs curvatures and by the way, the contact conditions with the underlaying layers. So it is absolutely necessary to take into account this effect in the design of the ballastless track structures in order to guarantee a long target life of at least of 50 years. After design and experimental tests in laboratory, a real ballastless track structure of 1km was built in France at the beginning of year 2013. This structure has 2 tracks on which several trains circulate every day since the beginning of year 2014. Before the construction, it was decided to monitor this structure to verify that the mechanical behavior is conform to the simulations. One part of the instrumentation is dedicated to monitor quasi-continuously the evolution of the curvature of a concrete slab. For this, 2 accelerometers were fixed on the slab under the track. One was placed on the edge and the other in the middle of the slab. The acquisition of the signals by a

  5. Using Tri-Axial Accelerometers to Assess the Dynamic Control of Head Posture During Gait

    Science.gov (United States)

    Lawrence, John H., III

    2003-01-01

    Long duration spaceflight is known to cause a variety of biomedical stressors to the astronaut. One of the more functionally destabilizing effects of spaceflight involves microgravity-induced changes in vestibular or balance control. Balance control requires the integration of the vestibular, visual, and proprioceptive systems. In the microgravity environment, the normal gravity vector present on Earth no longer serves as a reference for the balance control system. Therefore, adaptive changes occur to the vestibular system to affect control of body orientation with altered, or non-present, gravity and/or proprioceptive inputs. Upon return to a gravity environment, the vestibular system must re-incorporate the gravity vector and gravity-induced proprioceptive inputs into the balance control regime. The result is often a period of postural instability, which may also be associated with space motion sickness (oscillopsia, nausea, and vertigo). Previous studies by the JSC Neuroscience group have found that returning astronauts often employ alterations in gait mechanics to maintain postural control during gait. It is believed that these gait alterations are meant to decrease the transfer of heel strike shock energy to the head, thus limiting the contradictory head and eye movements that lead to gait instability and motion sickness symptoms. We analyzed pre- and post-spaceflight tri-axial accelerometer data from the NASA/MIR long duration spaceflight missions to assess the heel to head transfer of heel strike shock energy during locomotion. Up to seven gait sessions (three preflight, four postflight) of head and shank (lower leg) accelerometer data was previously collected from six astronauts who engaged in space flights of four to six months duration. In our analysis, the heel to head transmission of shock energy was compared using peak vertical acceleration (a), peak jerk (j) ratio, and relative kinetic energy (a). A host of generalized movement variables was produced

  6. Properties of Traveling Atmospheric Disturbances (TADs) Inferred From CHAMP and GRACE Accelerometer Observations

    Science.gov (United States)

    Bruinsma, S. L.; Forbes, J. M.

    2008-12-01

    The accelerometers on the CHAMP and GRACE satellites have made it possible to accumulate near- continuous records of thermosphere density between about 370 and 490 km since May 2001, and July 2002, respectively. They have recorded the response to virtually every significant geomagnetic storm during this period. CHAMP and GRACE are in (near) polar and quasi-circular orbits, sampling 24 hr local time approximately every 4 and 5 months, respectively. These capabilities offer unique opportunities to study the temporal and latitudinal responses of the thermosphere to geomagnetic disturbances. Data from initially 34 geomagnetic storms were explored, but significant and unambiguous TAD activity in the observed response of the thermosphere was detected for about half the events. The atmospheric variability is evaluated by de-trending the data, allowing the extraction of specific ranges in horizontal scale, and analyzing density "residuals". The scale of the perturbation is decisive for its lifetime and relative amplitude. Sometimes the disturbances represent wave-like structures propagating far from the source, and these so- called 'TADs' were detected and described for the May 2003 storm for the first time. Some TADs traveled over the pole into the opposite hemisphere; this was found in both CHAMP and GRACE data. Most TADs propagate equatorward, but poleward propagating TADs have on occasion been detected too. The estimated speeds of the observed TADs are of the order of 400-900 m/s, and their mean scale is approximately 2000 km. The TADs observed with GRACE are significantly slower than those seen in the CHAMP data. The opposite is expected from theory: speed increasing with altitude.

  7. Dynamic Response Assessment for the MEMS Accelerometer Under Severe Shock Loads

    Science.gov (United States)

    Fan, Mark S.; Shaw, Harry C.

    2001-01-01

    NASA Goddard Space Flight Center (GSFC) has evaluated the dynamic response of a commercial-off-the-shelf (COTS) microelectromechanical systems (MEMS) device made by Analog Device, Inc. The device is designated as ADXL250 and is designed mainly for sensing dynamic acceleration. It is also used to measure the tilting angle of any system or component from its original level position. The device has been in commercial use (e.g., in automobile airbag deployment system as a dual-axial accelerometer and in the electronic game play-station as a tilting sensor) with success, but NASA needs an in-depth assessment of its performance under severe dynamic shock environments. It was realized while planning this evaluation task that two assessments would be beneficial to NASA's missions: (1) severe dynamic shock response under nominal thermal environments; and (2) general dynamic performance under cryogenic environments. The first evaluation aims at obtaining a good understanding of its micromachined structure within a framework of brittle fracture dynamics, while the second evaluation focuses on the structure integrity under cryogenic temperature conditions. The information we gathered from the manufacturer indicated that the environmental stresses under NASA's evaluation program have been far beyond what the device has experienced with commercial applications, for which the device was designed. Thus NASA needs the outcome of this evaluation in order to make the selection for possible use for its missions. This paper provides details of the first evaluation the dynamic response under severe multi-axial single-pulse shock load. It was performed using finite element tools with nonlinear dynamics procedures.

  8. Equating accelerometer estimates of moderate-to-vigorous physical activity: in search of the Rosetta Stone.

    Science.gov (United States)

    Bornstein, Daniel B; Beets, Michael W; Byun, Wonwoo; Welk, Greg; Bottai, Matteo; Dowda, Marsha; Pate, Russell

    2011-09-01

    No universally accepted ActiGraph accelerometer cutpoints for quantifying moderate-to-vigorous physical activity (MVPA) exist. Estimates of MVPA from one set of cutpoints cannot be directly compared to MVPA estimates using different cutpoints, even when the same outcome units are reported (MVPA mind(-1)). The purpose of this study was to illustrate the utility of an equating system that translates reported MVPA estimates from one set of cutpoints into another, to better inform public health policy. Secondary data analysis. ActiGraph data from a large preschool project (N=419, 3-6-yr-olds, CHAMPS) was used to conduct the analyses. Conversions were made among five different published MVPA cutpoints for children: Pate (PT), Sirard (SR), Puyau (PY), Van Cauwengerghe (VC), and Freedson Equation (FR). A 10-fold cross-validation procedure was used to develop prediction equations using MVPA estimated from each of the five sets of cutpoints as the dependent variable, with estimated MVPA from one of the other four sets of cutpoints (e.g., PT MVPA predicted from FR MVPA). The mean levels of MVPA for the total sample ranged from 22.5 (PY) to 269.0 (FR) mind(-1). Across the prediction models (5 total), the median proportion of variance explained (R(2)) was 0.76 (range 0.48-0.97). The median absolute percent error was 17.2% (range 6.3-38.4%). The prediction equations developed here allow for direct comparisons between studies employing different ActiGraph cutpoints in preschool-age children. These prediction equations give public health researchers and policy makers a more concise picture of physical activity levels of preschool-aged children. PMID:21524938

  9. Attitude determination with three-axis accelerometer for emergency atmospheric entry

    Science.gov (United States)

    Garcia-Llama, Eduardo (Inventor)

    2012-01-01

    Two algorithms are disclosed that, with the use of a 3-axis accelerometer, will be able to determine the angles of attack, sideslip and roll of a capsule-type spacecraft prior to entry (at very high altitudes, where the atmospheric density is still very low) and during entry. The invention relates to emergency situations in which no reliable attitude and attitude rate are available. Provided that the spacecraft would not attempt a guided entry without reliable attitude information, the objective of the entry system in such case would be to attempt a safe ballistic entry. A ballistic entry requires three controlled phases to be executed in sequence: First, cancel initial rates in case the spacecraft is tumbling; second, maneuver the capsule to a heat-shield-forward attitude, preferably to the trim attitude, to counteract the heat rate and heat load build up; and third, impart a ballistic bank or roll rate to null the average lift vector in order to prevent prolonged lift down situations. Being able to know the attitude, hence the attitude rate, will allow the control system (nominal or backup, automatic or manual) to cancel any initial angular rates. Also, since a heat-shield forward attitude and the trim attitude can be specified in terms of the angles of attack and sideslip, being able to determine the current attitude in terms of these angles will allow the control system to maneuver the vehicle to the desired attitude. Finally, being able to determine the roll angle will allow for the control of the roll ballistic rate during entry.

  10. Measured and perceived environmental characteristics are related to accelerometer defined physical activity in older adults

    Directory of Open Access Journals (Sweden)

    Strath Scott J

    2012-04-01

    Full Text Available Abstract Background Few studies have investigated both the self-perceived and measured environment with objectively determined physical activity in older adults. Accordingly, the aim of this study was to examine measured and perceived environmental associations with physical activity of older adults residing across different neighborhood types. Methods One-hundred and forty-eight older individuals, mean age 64.3 ± 8.4, were randomly recruited from one of four neighborhoods that were pre-determined as either having high- or low walkable characteristics. Individual residences were geocoded and 200 m network buffers established. Both objective environment audit, and self-perceived environmental measures were collected, in conjunction with accelerometer derived physical activity behavior. Using both perceived and objective environment data, analysis consisted of a macro-level comparison of physical activity levels across neighborhood, and a micro-level analysis of individual environmental predictors of physical activity levels. Results Individuals residing in high-walkable neighborhoods on average engaged in 11 min of moderate to vigorous physical activity per day more than individuals residing in low-walkable neighborhoods. Both measured access to non-residential destinations (b = .11, p p = .031 were significant predictors of time spent in moderate to vigorous physical activity. Other environmental variables significantly predicting components of physical activity behavior included presence of measured neighborhood crime signage (b = .4785, p = .031, measured street safety (b = 26.8, p = .006, and perceived neighborhood satisfaction (b = .5.8, p = .003. Conclusions Older adult residents who live in high-walkable neighborhoods, who have easy and close access to nonresidential destinations, have lower social dysfunction pertinent to crime, and generally perceive the neighborhood to a higher overall satisfaction are likely to engage in higher levels

  11. Reliability and comparability of the accelerometer and the linear position measuring device in resistance training.

    Science.gov (United States)

    Gomez-Piriz, Pedro T; Sanchez, Eva T; Manrique, David C; Gonzalez, Esther P

    2013-06-01

    The purpose of this study was to determine the intermachine reliability attained from devices used to measure the common variables in sports performance. Repeatability conditions were established by creating a similar set of conditions under which the measurements were taken from both devices. The objectives of this research were to demonstrate the reliability between two devices in a bench press movement--the linear position measuring device (LPM) isoinertial dynamometer (T-Force) and the 3D (Myotest) accelerometer (AC)--and to compare the existing correlations between maximum velocity, maximum estimated strength, and peak power estimate variables in the bench press exercise. Forty bench press exercise trials were analyzed simultaneously, performed by 3 different subjects (age: 26.74 ± 1.2 years, height: 175.74 ± 4.04 cm, weight: 78.7 ± 3.35 kg) at maximum velocity (25 kg additional load). Three simple linear regression models were developed, supplied by the LPM on the basis of the AC data. The assumption of independence of errors was compared by means of the Durban-Watson test, and partial autocorrelation coefficients were established at an overall p < 0.05 significance level. It has not been possible to confirm the presence of a general correlation between the measurements of both devices. Regarding the assumption of independence of errors, the presence of generalized autocorrelation was confirmed. Linear regression analysis revealed an intermachine correlation in one of the nonconclusive cases, (peak power) variable and subject 1, r (10) = 0.640, p = 0.024. No partial autocorrelation was found. The devices should not be used interchangeably as instruments. PMID:22847523

  12. Accelerometer measurement of upper extremity movement after stroke: a systematic review of clinical studies.

    Science.gov (United States)

    Noorkõiv, Marika; Rodgers, Helen; Price, Christopher I

    2014-10-09

    The aim of this review was to identify and summarise publications, which have reported clinical applications of upper limb accelerometry for stroke within free-living environments and make recommendations for future studies. Data was searched from MEDLINE, Scopus, IEEExplore and Compendex databases. The final search was 31st October 2013. Any study was included which reported clinical assessments in parallel with accelerometry in a free-living hospital or home setting. Study quality is reflected by participant numbers, methodological approach, technical details of the equipment used, blinding of clinical measures, whether safety and compliance data was collected. First author screened articles for inclusion and inclusion of full text articles and data extraction was confirmed by the third author. Out of 1375 initial abstracts, 8 articles were included. All participants were stroke patients. Accelerometers were worn for either 24 hours or 3 days. Data were collected as summed acceleration counts over a specified time or as the duration of active/inactive periods. Activity in both arms was reported by all studies and the ratio of impaired to unimpaired arm activity was calculated in six studies. The correlation between clinical assessments and accelerometry was tested in five studies and significant correlations were found. The efficacy of a rehabilitation intervention was assessed using accelerometry by three studies: in two studies both accelerometry and clinical test scores detected a post-treatment difference but in one study accelerometry data did not change despite clinical test scores showing motor and functional improvements. Further research is needed to understand the additional value of accelerometry as a measure of upper limb use and function in a clinical context. A simple and easily interpretable accelerometry approach is required.

  13. Smartstones: a small e-compass, accelerometer and gyroscope embedded in stones

    Science.gov (United States)

    Gronz, Oliver; Hiller, Priska H.; Wirtz, Stefan; Becker, Kerstin; Iserloh, Thomas; Aberle, Jochen; Casper, Markus C.

    2015-04-01

    produced only sub-Nyquist sampling values and the rotation velocity of the pebble could not be derived correctly using solely the device's data. Consequently, the device's software was adapted by the developers: the second (and current) version of the device only acquires acceleration and compass, as the acquisition of the gyroscope's value does not allow for higher sampling rates. The second version samples every 12 ms. All aforementioned experiments have been repeated using the adapted device. For data analysis, the high-speed camera images were merged with the device data using a MATLAB script. Furthermore, the derived relative pebble orientation - yaw, pitch and roll - is illustrated using a rotated CAD model of the pebble. The pebble's orientation is derived from compass and accelerometer data using sensor fusion and algorithms for tilt compensated compasses. The results show that the device is perfectly able to capture the movement of the pebble such as rotation (including the rotation axis), sliding or saltation. The interacting forces between the pebble and the underground can be calculated from the acceleration data. However, the accelerometer data also showed that the range of the sensor is not sufficiently large: clipping of values occurred. According to present instrument specifications, the sensor is able to capture up to 4 g for each axis but the resulting vectors for acceleration along all three axes showed values greater than 4 g, even up to the theoretical maximum of approximately 6.9 g. Thus, an impact of this strength that only stresses one axis cannot be measured. As a result of this clipping, the derivation of the pebble's absolute position using double integration of acceleration values is associated with flaws. Besides this clipping, the derived position will deviate from the true position for larger distances or longer experiment durations as the noise of the data will be integrated, too. Several requirements for the next device version were

  14. Application of MEMS accelerometer on micro-robots%MEMS加速度传感器在微型特种机器人中的应用

    Institute of Scientific and Technical Information of China (English)

    陈卫; 杨忠; 夏玉亮; 樊琼剑

    2009-01-01

    提出一种基于MEMS加速度传感器LISLV02DL的特种机器人姿态测控和环境感知方案.阐述了系统硬件组成,分析了传感器姿态测控方法和环境感知原理.为提高加速度传感器工作精度,设计了一种加速度传感器校正方法.试验结果表明:该加速度传感器能较好地感知机器人运动的姿态与方向,并实现机器人着陆姿态调整和外部环境振动信息的监测.%The application of environmental perception and micro-robot attitude measurement and control is developed based on a 3-axis MEMS accelerometer with digital output LIS3LV02DL. The design of hardware system is introduced. The principle of environmental perception and micro-robot attitude measurement and control by accelerometer is analyzed. In order to improve the measuring precision of accelerometer, a calibrating method of accelerometers is presented. The results show that the accelerometer can percept the attitude and direction of the robot motion, adjust the robot landing attitude and monitor the vibration information of environment well.

  15. Validity of using tri-axial accelerometers to measure human movement - Part I: Posture and movement detection.

    Science.gov (United States)

    Lugade, Vipul; Fortune, Emma; Morrow, Melissa; Kaufman, Kenton

    2014-02-01

    A robust method for identifying movement in the free-living environment is needed to objectively measure physical activity. The purpose of this study was to validate the identification of postural orientation and movement from acceleration data against visual inspection from video recordings. Using tri-axial accelerometers placed on the waist and thigh, static orientations of standing, sitting, and lying down, as well as dynamic movements of walking, jogging and transitions between postures were identified. Additionally, subjects walked and jogged at self-selected slow, comfortable, and fast speeds. Identification of tasks was performed using a combination of the signal magnitude area, continuous wavelet transforms and accelerometer orientations. Twelve healthy adults were studied in the laboratory, with two investigators identifying tasks during each second of video observation. The intraclass correlation coefficients for inter-rater reliability were greater than 0.95 for all activities except for transitions. Results demonstrated high validity, with sensitivity and positive predictive values of greater than 85% for sitting and lying, with walking and jogging identified at greater than 90%. The greatest disagreement in identification accuracy between the algorithm and video occurred when subjects were asked to fidget while standing or sitting. During variable speed tasks, gait was correctly identified for speeds between 0.1m/s and 4.8m/s. This study included a range of walking speeds and natural movements such as fidgeting during static postures, demonstrating that accelerometer data can be used to identify orientation and movement among the general population. PMID:23899533

  16. The Study for SOIC Package Technology of MEMS Accelerometer%MEMS加速计的SOIC封装技术研究

    Institute of Scientific and Technical Information of China (English)

    李辉; 廖巨华; 须自明

    2013-01-01

    The paper studied the characteristic of MEMS (microelectromechanical systems) accelerometer in SOIC package, it analysed the main packaging process steps which affect the PPM based on the reason of MEMS chip fracture failure. Induction unit solid crystal glue hardness is the main parameters which cause chip fracture, by reverse engineering, solid crystal material which can meet both the induction unit natural frequency and package reliability requirements can be confirmed. Test using a solid crystal glue E, the MEMS accelerometer SOIC package showing a more robust features. This study has some reference value for improving MEMS accelerometer PPM.%文中通过研究MEMS(微机电系统)加速计在SOIC封装(小外形集成电路封装)下的特性,针对MEMS芯片断裂故障的原因分析了影响PPM(百万分比的缺陷率)性能的主要封装工艺步骤。其中感应单元固晶胶的硬度是引起芯片断裂的主要参数,通过反向工程确定了可以同时满足感应单元固有频率和封装可靠性要求的固晶材料。在试验中采用固晶胶E后,MEMS加速计的SOIC封装呈现出更加强韧的特性。此研究对于改善MEMS加速计的PPM性能有一定参考价值。

  17. Use of three-dimensional accelerometers to evaluate behavioral changes in cattle experimentally infected with bovine viral diarrhea virus.

    Science.gov (United States)

    Bayne, Jenna E; Walz, Paul H; Passler, Thomas; White, Brad J; Theurer, Miles E; van Santen, Edzard

    2016-06-01

    OBJECTIVE To assess the use of 3-D accelerometers to evaluate behavioral changes in cattle experimentally infected with a low-virulent strain of bovine viral diarrhea virus (BVDV). ANIMALS 20 beef steers (mean weight, 238 kg). PROCEDURES Calves were allocated to a BVDV (n = 10) or control (10) group. On day 0, calves in the BVDV group were inoculated with a low-virulent strain of BVDV (4 × 10(6) TCID50, intranasally), and calves in the control group were sham inoculated with BVDV-free medium (4 mL; intranasally). An accelerometer was affixed to the right hind limb of each calf on day -7 to record activity (lying, walking, and standing) continuously until 35 days after inoculation. Baseline was defined as days -7 to -1. Blood samples were collected at predetermined times for CBC, serum biochemical analysis, virus isolation, and determination of anti-BVDV antibody titers. RESULTS All calves in the BVDV group developed viremia and anti-BVDV antibodies but developed only subclinical or mild disease. Calves in the control group did not develop viremia or anti-BVDV antibodies. Mean time allocated to each activity did not differ significantly between the BVDV and control groups on any day except day 8, when calves in the BVDV group spent less time standing than the calves in the control group. Following inoculation, calves in both groups tended to spend more time lying and less time walking and standing than they did during baseline. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that behavioral data obtained by accelerometers could not distinguish calves subclinically infected with BVDV from healthy control calves. However, subtle changes in the behavior of the BVDV-infected calves were detected and warrant further investigation. PMID:27227496

  18. Comparison of capacitive and frequential readout when scaling accelerometers down from Micro- to Nano- Electro Mechanical Systems

    CERN Document Server

    Hentz, Sébastien; Colinet, Eric

    2012-01-01

    This paper shows the effect of scaling silicon accelerometers down from MEMS to NEMS. It models both electronics and Brownian noise sources for both capacitive and resonant devices, and computes the minimum detectable signal attainable. Computed results are remarkably close to published experimental results. It shows the relatively low influence of the quality factor and of the beam width in the resonant case. Different scaling rules are investigated, and it appears that resonant sensing may satisfy some new application requirements, in particular for critical dimensions below a few hundreds of nm, when it is better resolved than capacitive sensing.

  19. Medium-scale gravity waves in the mid-/low-latitude dayside upper thermosphere as observed by the CHAMP accelerometer

    OpenAIRE

    J. Park; H. Lühr

    2014-01-01

    Although a number of studies had investigated gravity waves (GWs) in the upper thermosphere, details of their global climatology at mid-/low-latitudes remained unknown. Here we report a detailed climatology of the medium-scale (150-600 km) GW in the mid-/low-latitude dayside upper thermosphere, as observed by the CHAMP accelerometer (at about 300-400 km altitude) from 2001 to 2010. The mid-latitude GWs exhibit higher activity in the winter hemisphere than in the summer hemisphere. GWs near th...

  20. Accelerometer Measured Level of Physical Activity Indoors and Outdoors During Preschool Time in Sweden and the United States

    DEFF Research Database (Denmark)

    Raustorp, A.; Pagels, P.; Boldemann, C.;

    2012-01-01

    boys and girls indoor and outdoor physical activity regarding different intensity levels and sedentary behaviour. METHODS: Accelerometer determined physical activity in 50 children with mean age 52 months, (range 40-67) was recorded during preschool time for 5 consecutive weekdays at four sites. The......BACKGROUND: It is important to understand the correlates of physical activity in order to influence policy and create environments that promote physical activity among preschool children. We compared preschoolers' physical activity in Swedish and in US settings and objectively examined differences...

  1. Temperature compensated digital inertial sensor. [circuit for maintaining inertial element of gyroscope or accelerometer at constant position

    Science.gov (United States)

    Hand, P. J.

    1974-01-01

    A circuit which maintains the inertial element of a gyroscope or accelerometer at a constant position by delivering pulses to a rebalancing motor is discussed. The circuit compensates for temperature changes by using a temperature sensor that varies the threshold of inertial element movement required to generate a rebalance pulse which reacts to changes in viscosity of the flotation fluid. The output of the temperature sensor also varies the output level of the current source to compensate for changes in the strength of the magnets of the rebalancing motor. The sensor also provides a small signal to the rebalance motor to provide a temperature dependent compensation for fixed drift or fixed bias.

  2. POD improvements of GALILEO satellites through the measurement of their non-gravitational accelerations by means of an onboard accelerometer

    Science.gov (United States)

    Peron, Roberto; Lucchesi, David M.; Santoli, Francesco; Iafolla, Valerio; Fiorenza, Emiliano; Lefevre, Carlo; Lucente, Marco; Magnafico, Carmelo; Kalarus, Maciej; Zielinski, Janusz

    2016-04-01

    The Precise Orbit Determination (POD) of the satellites of the Global Navigation Satellite Systems (GNSS) represents the basic prerequisite in order to provide refined ephemerides for their orbit, aimed at providing a precise and accurate positioning on the Earth. An important factor that impacts negatively in the POD of these satellites is the limited modeling of the accelerations produced by the non-gravitational accelerations. These, indeed, are subtle and generally complex to model properly, especially in the case of a complex in shape spacecraft, with solar panels and antennae for microwave link and the mutual shadowing effects among the many surfaces involved. We have to notice that their modeling has an important impact in the determination of a number of geophysical parameters of interest, such as stations coordinates, Earth's geocenter and orientation parameters. In the case of GNSS satellites, the main NGP acceleration is the one produced by the direct solar radiation pressure, with non-negligible contributions due to Earth's albedo, thermal effects and power radiated by the antennae. The models developed so far for these perturbative effects have shown many limits, as pointed out in the literature. Currently, the models developed for the NGPs are mainly based on empirical blind models (with the goal of absorb unknowns quantities) and more recently with the use of wing-box models, that try to provide a finite-elements approach to the modeling. The European Space Agency (ESA) - in the context of the development of the GALILEO constellation, and especially in view of the next generation of GALILEO spacecraft - besides being interested in possible improvements of the NGPs models, is also envisaging the use of an onboard accelerometer to directly measure them in order to improve the POD of each spacecraft of the constellation. We have been involved in this study by means of a proposal to ESA denominated GALileo and ACcelerometry (GALAC) led by the Space

  3. Changes in physical activity over time in young children: a longitudinal study using accelerometers.

    Directory of Open Access Journals (Sweden)

    Rachael W Taylor

    Full Text Available Previous research has suggested that marked declines in physical activity occur during the preschool years, and across the transition into school. However, longitudinal studies using objective measures of activity have been limited by sample size and length of follow-up. The aims of this study were to determine how overall activity and time in different intensities of activity change in children followed from 3 to 7 years. Children (n = 242 wore Actical accelerometers at 3, 4, 5, 5.5, 6.5 and 7 years of age during all waking and sleeping hours for a minimum of 5 days. Time in sedentary (S, light (L, moderate (M, and vigorous (V physical activity was determined using available cut points. Data were analyzed using a mixed model and expressed as counts per minute (cpm, overall activity and the ratio of active time to sedentary time (LMV:S, adjusted for multiple confounders including sex, age, time worn, and weather. At 5 years, physical activity had declined substantially to around half that observed at 3 years. Although starting school was associated with a further short-term (6-month decline in activity (cpm in both boys (difference; 95% CI: -98; -149, -46 and girls (-124; -174, -74, both P<0.001, this proved to be relatively transient; activity levels were similar at 6-7 years as they were just prior to starting school. Boys were more physically active than girls as indicated by an overall 12% (95% CI: 2, 22% higher ratio of active to sedentary time (P = 0.014, but the pattern of this difference did not change from 3 to 7 years. Time worn and weather variables were significant predictors of activity. In conclusion, both boys and girls show a marked decline in activity from 3 to 4 years of age, a decrease that is essentially maintained through to 7 years of age. Factors driving this marked decrease need to be determined to enable the development of targeted interventions.

  4. An Earthquake Shake Map Routine with Low Cost Accelerometers: Preliminary Results

    Science.gov (United States)

    Alcik, H. A.; Tanircan, G.; Kaya, Y.

    2015-12-01

    Vast amounts of high quality strong motion data are indispensable inputs of the analyses in the field of geotechnical and earthquake engineering however, high cost of installation of the strong motion systems constitutes the biggest obstacle for worldwide dissemination. In recent years, MEMS based (micro-electro-mechanical systems) accelerometers have been used in seismological research-oriented studies as well as earthquake engineering oriented projects basically due to precision obtained in downsized instruments. In this research our primary goal is to ensure the usage of these low-cost instruments in the creation of shake-maps immediately after a strong earthquake. Second goal is to develop software that will automatically process the real-time data coming from the rapid response network and create shake-map. For those purposes, four MEMS sensors have been set up to deliver real-time data. Data transmission is done through 3G modems. A subroutine was coded in assembler language and embedded into the operating system of each instrument to create MiniSEED files with packages of 1-second instead of 512-byte packages.The Matlab-based software calculates the strong motion (SM) parameters at every second, and they are compared with the user-defined thresholds. A voting system embedded in the software captures the event if the total vote exceeds the threshold. The user interface of the software enables users to monitor the calculated SM parameters either in a table or in a graph (Figure 1). A small scale and affordable rapid response network is created using four MEMS sensors, and the functionality of the software has been tested and validated using shake table tests. The entire system is tested together with a reference sensor under real strong ground motion recordings as well as series of sine waves with varying amplitude and frequency. The successful realization of this software allowed us to set up a test network at Tekirdağ Province, the closest coastal point to

  5. A combined modulated feedback and temperature compensation approach to improve bias drift of a closed-loop MEMS capacitive accelerometer

    Institute of Scientific and Technical Information of China (English)

    Ming-jun MA; Zhong-he JIN‡; Hui-jie ZHU

    2015-01-01

    The bias drift of a micro-electro-mechanical systems (MEMS) accelerometer suffers from the 1/f noise and the tem-perature effect. For massive applications, the bias drift urgently needs to be improved. Conventional methods often cannot ad-dress the 1/f noise and temperature effect in one architecture. In this paper, a combined approach on closed-loop architecture modification is proposed to minimize the bias drift. The modulated feedback approach is used to isolate the 1/f noise that exists in the conventional direct feedback approach. Then a common mode signal is created and added into the closed loop on the basis of modulated feedback architecture, to compensate for the temperature drift. With the combined approach, the bias instability is improved to less than 13 µg, and the drift of the Allan variance result is reduced to 17 µg at 100 s of the integration time. The temperature coefficient is reduced from 4.68 to 0.1 mg/°C. The combined approach could be useful for many other closed-loop accelerometers.

  6. Intermonitor reliability of the GT3X+ accelerometer at hip, wrist and ankle sites during activities of daily living

    International Nuclear Information System (INIS)

    The triaxial GT3X+ accelerometer can measure activity counts in the vertical, horizontal right to left, horizontal front to back planes, and can generate a summative score of the three axes represented by vector magnitude (VM). Information on the reliability of the GT3X+ at the hip, wrist and ankle sites, over all axes and VM during activities of daily living (ADL) is lacking in the literature. Forty healthy adults (14 men and 26 women) were randomly assigned to perform 10 of 20 ADL (consisting of sedentary, housework, yard work, locomotive and recreational activities) while wearing two monitors on the hip, wrist and ankle. Subjects performed each ADL over 7 min and the mean activity counts during the last 4 min were used for analyses. Average intraclass correlations between monitors were high for the three sites for each axis and VM (hip: 0.943, 0.857, 0.864 and 0.966, respectively; wrist: 0.994, 0.963, 0.961 and 0.989, respectively; ankle: 0.977, 0.979, 0.927 and 0.986, respectively). These data suggest that GT3X+ accelerometers measurements made from the hip, wrist and ankle sites are reliable during ADL across all axes and VM. (paper)

  7. Rancang Bangun Permainan Edukasi Matematika dan Fisika dengan Memanfaatkan Accelerometer dan Physics Engine Box2d pada Android

    Directory of Open Access Journals (Sweden)

    Putri Nikensasi

    2012-09-01

    Full Text Available Perkembangan industri permainan mobil yang semakin meningkat memotivasi para pengembang permainan mobil untuk membuat inovasi-inovasi terbaru dalam permainannya. Salah satu inovasi tersebut yaitu permainan edukasi, namun saat ini permainan edukasi kurang diminati karena aturan permainannya yang cenderung membosankan. Pengembangan permainan ini ditujukan untuk membuat sebuah permainan mobil edukasi dengan memanfaatkan teknologi mobil terbaru dalam aturan permainannya sehingga permainan tersebut tidak membosankan. Aplikasi yang dikembangkan merupakan aplikasi permainan mobil edukasi yang mengajarkan ilmu matematika dan fisika kepada pemainnya. Teknologi baru yang digunakan dalam permainan ini yaitu accelerometer pada sistem operasi Android yang diintegrasikan dengan Physics Engine Library Box2D. Selain itu, permainan ini dibangun dengan menggunakan Adobe Flash CS5.5 dan bahasa pemrograman Actionscript 3 (AS3 serta Adobe Air sebagai runtime aplikasinya. Uji coba dilakukan dengan menggunakan perangkat Android versi 2.3. Dari uji coba dapat disimpulkan bahwa Adobe Flash CS5.5 dapat digunakan untuk membuat permainan mobil edukasi pada perangkat Android dan mengakses sensor accelerometer-nya.

  8. Comparison of macrobend seismic optical fiber accelerometer and ferrule-top cantilever fiber sensor for vibration monitoring

    Science.gov (United States)

    Poczęsny, Tomasz; Prokopczuk, Krzysztof; Domański, Andrzej W.

    2012-04-01

    The paper presents the exemplary application and comparison of a macrobend seismic optical fiber accelerometer and ferrule-top cantilever fiber sensor for long distance vibration monitoring with use of typical telecommunication optical transmission systems including optical fibers, transmitters and receivers. Use of telecommunication optical systems allows developing cost-effective monitoring and sensing architecture. All-optical fiber sensors do not create any fire hazard due to transmitting low power light through the optical fibers and lack of electrically driven parts in sensing part. Optical fiber macrobend seismic sensor consists of single mode optical fiber bended into a loop of radius around few millimeters with attached small seismic mass around 0.3 grams. We achieve signal that is proportional to the geometrical deformation of the loop. The ferrule-top cantilever (made by Optics11 - Amsterdam, Netherlands) optical fiber sensor is fabricated on a rectangular 3 mm x 3mm x 7 mm glass ferrule equipped with a central borehole and laser curved cantilever with dimensions of 200 microns wide, 30 microns thick and around 3 mm long. Construction allows measuring bending of the cantilever. Both optical fiber sensors in this setup measure force and acceleration similar to the piezoelectric accelerometers. The advantage of these devices is insensitivity to electromagnetic interference because of all-optical sensor head. We compared parameters and measurement capabilities of both sensor types.

  9. Children's Physical Activity Behavior during School Recess: A Pilot Study Using GPS, Accelerometer, Participant Observation, and Go-Along Interview.

    Science.gov (United States)

    Pawlowski, Charlotte Skau; Andersen, Henriette Bondo; Troelsen, Jens; Schipperijn, Jasper

    2016-01-01

    Schoolyards are recognized as important settings for physical activity interventions during recess. However, varying results have been reported. This pilot study was conducted to gain in-depth knowledge of children's physical activity behavior during recess using a mixed-methods approach combining quantitative GPS and accelerometer measurements with qualitative go-along group interviews and participant observations. Data were collected during three weekdays in a public school in Denmark. Eighty-one children (47 girls) wore an accelerometer (ActiGraph GT3X) and GPS (QStarz BT-Q1000xt), sixteen children participated in go-along group interviews, and recess behavior was observed using an ethnographical participant observation approach. All data were analyzed separated systematically answering the Five W Questions. Children were categorized into Low, Middle and High physical activity groups and these groups were predominantly staying in three different locations during recess: school building, schoolyard and field, respectively. Mostly girls were in the building remaining in there because of a perceived lack of attractive outdoor play facilities. The children in the schoolyard were predominantly girls who preferred the schoolyard over the field to avoid the competitive soccer games on the field whereas boys dominated the field playing soccer. Using a mixed-methods approach to investigate children's physical activity behavior during recess helped gain in-depth knowledge that can aid development of future interventions in the school environment. PMID:26859288

  10. Children's Physical Activity Behavior during School Recess: A Pilot Study Using GPS, Accelerometer, Participant Observation, and Go-Along Interview.

    Directory of Open Access Journals (Sweden)

    Charlotte Skau Pawlowski

    Full Text Available Schoolyards are recognized as important settings for physical activity interventions during recess. However, varying results have been reported. This pilot study was conducted to gain in-depth knowledge of children's physical activity behavior during recess using a mixed-methods approach combining quantitative GPS and accelerometer measurements with qualitative go-along group interviews and participant observations. Data were collected during three weekdays in a public school in Denmark. Eighty-one children (47 girls wore an accelerometer (ActiGraph GT3X and GPS (QStarz BT-Q1000xt, sixteen children participated in go-along group interviews, and recess behavior was observed using an ethnographical participant observation approach. All data were analyzed separated systematically answering the Five W Questions. Children were categorized into Low, Middle and High physical activity groups and these groups were predominantly staying in three different locations during recess: school building, schoolyard and field, respectively. Mostly girls were in the building remaining in there because of a perceived lack of attractive outdoor play facilities. The children in the schoolyard were predominantly girls who preferred the schoolyard over the field to avoid the competitive soccer games on the field whereas boys dominated the field playing soccer. Using a mixed-methods approach to investigate children's physical activity behavior during recess helped gain in-depth knowledge that can aid development of future interventions in the school environment.

  11. Development of a noncontact heart rate monitoring system for sedentary behavior based on an accelerometer attached to a chair

    International Nuclear Information System (INIS)

    Although people spend a third of their day engaged in sedentary activities, research on heart activity during sitting is almost nonexistent because of the discomfort experienced when electrocardiogram (ECG) measurement electrodes are attached to the body. Accordingly, in this study, a system was developed to monitor heart rate (HR) in a noncontact and unconstrained way while subjects were seated, by attaching an accelerometer on the backrest of a chair. Acceleration signals were obtained three times from 20 healthy adults, a detection algorithm was applied, and HR detection performance was evaluated by comparing the R-peak values from the ECG. The system had excellent performance results, with a sensitivity of 96.10% and a positive predictive value of 96.43%. In addition, the HR calculated by the new system developed in this study was compared with HR calculated using ECG. The new system exhibited excellent performance; its results were strongly correlated with that of ECG (r = 0.97, p ≪ 0.0001; average difference of −0.08  ±  4.60 [mean ± 1.96∙standard deviation] in Bland–Altman analysis). Accordingly, the method presented in this study is expected to be applicable for evaluating diverse autonomic nervous system components in a noncontact and unconstrained way using an accelerometer to monitor the HR of sedentary workers or adolescents. (note)

  12. Recognition of elementary arm movements using orientation of a tri-axial accelerometer located near the wrist

    International Nuclear Information System (INIS)

    In this paper we present a method for recognising three fundamental movements of the human arm (reach and retrieve, lift cup to mouth, rotation of the arm) by determining the orientation of a tri-axial accelerometer located near the wrist. Our objective is to detect the occurrence of such movements performed with the impaired arm of a stroke patient during normal daily activities as a means to assess their rehabilitation. The method relies on accurately mapping transitions of predefined, standard orientations of the accelerometer to corresponding elementary arm movements. To evaluate the technique, kinematic data was collected from four healthy subjects and four stroke patients as they performed a number of activities involved in a representative activity of daily living, ‘making-a-cup-of-tea’. Our experimental results show that the proposed method can independently recognise all three of the elementary upper limb movements investigated with accuracies in the range 91–99% for healthy subjects and 70–85% for stroke patients. (paper)

  13. Comparison of estimated energy intake in children using a Web-based Dietary Assessment Software with accelerometer-estimated energy expenditure in children

    DEFF Research Database (Denmark)

    Biltoft-Jensen, Anja Pia; Hjort, Mads F.; Trolle, Ellen;

    2013-01-01

    in Denmark. Dietary assessment was carried out using a program known as WebDASC (Web-based Dietary Assessment Software for Children) to collect data from the children. Objective To compare the energy intake (EI) of schoolchildren aged 8–11 estimated using the WebDASC system against the total energy...... an accelerometer for two periods of seven consecutive days: at baseline, when they ate their usual packed lunches and at intervention when they were served the NND. EI was estimated using WebDASC, and TEE was calculated from accelerometer-derived activity energy expenditure, basal metabolic rate, and diet...

  14. Mother-reported sleep, accelerometer-estimated sleep and weight status in Mexican American children: sleep duration is associated with increased adiposity and risk for overweight/obese status

    Science.gov (United States)

    We know of no studies comparing parent-reported sleep with accelerometer-estimated sleep in their relation to paediatric adiposity. We examined: (i) the reliability of mother-reported sleep compared with accelerometer-estimated sleep; and (ii) the relationship between both sleep measures and child a...

  15. High-resolution monitoring of bedload transport rates: a benchmark of two approaches (accelerometers and image processing)

    Science.gov (United States)

    Dhont, Blaise; Rousseau, Gauthier; Ancey, Christophe

    2016-04-01

    Experimental and field studies have shown how intermittent bedload transport can be at low flow rates. The development and validation of bedload-transport equations require high-resolution records over long periods of time. Two technologies are considered in the present investigation: image processing and accelerometers mounted on impact plates. The former has been successfully applied to monitor bedload transport in many flume experiments, and the latter has shown encouraging results at different field sites. Calibration is a major issue in both cases, and it is often difficult to assess the precision of the data collected. In our talk, we show how to calibrate and compare the performances of accelerometer and image-processing based techniques in laboratory conditions. The accelerometer is fixed on a perforated steel plate, which is placed vertically at the lower end of the flume. The vibrations due to the particles impacting the plate are recorded with a sampling frequency of 10 kHz. The proxy for bedload transport rate is chosen as the number of peaks above a fixed threshold of the recorded signal. Note that impact plates are usually set in flush with the bed, and to our knowledge, the vertical configuration presented here has not yet been documented. The experimental setup for image processing involves a video-camera that takes top-view images of the particles moving over a white board mounted at the outlet of the flume. Data storage poses an issue, which can be got round by pre-processing the images in real time. The bedload transport rate is estimated based on the number of particles that are identified on the images. The two technologies have the advantages of being cost-effective and demanding limited effort for implementation. They provide high-resolution bedload transport rates over several hours. Estimates of bedload discharge were found to be robust and accurate for low sediment transport rates. At higher rates, the sensors may saturate due the arrival

  16. Angular and Linear Velocity Estimation for a Re-Entry Vehicle Using Six Distributed Accelerometers: Theory, Simulation and Feasibility

    Energy Technology Data Exchange (ETDEWEB)

    Clark, G

    2003-04-28

    This report describes a feasibility study. We are interested in calculating the angular and linear velocities of a re-entry vehicle using six acceleration signals from a distributed accelerometer inertial measurement unit (DAIMU). Earlier work showed that angular and linear velocity calculation using classic nonlinear ordinary differential equation (ODE) solvers is not practically feasible, due to mathematical and numerical difficulties. This report demonstrates the theoretical feasibility of using model-based nonlinear state estimation techniques to obtain the angular and linear velocities in this problem. Practical numerical and calibration issues require additional work to resolve. We show that the six accelerometers in the DAIMU are not sufficient to provide observability, so additional measurements of the system states are required (e.g. from a Global Positioning System (GPS) unit). Given the constraint that our system cannot use GPS, we propose using the existing on-board 3-axis magnetometer to measure angular velocity. We further show that the six nonlinear ODE's for the vehicle kinematics can be decoupled into three ODE's in the angular velocity and three ODE's in the linear velocity. This allows us to formulate a three-state Gauss-Markov system model for the angular velocities, using the magnetometer signals in the measurement model. This re-formulated model is observable, allowing us to build an Extended Kalman Filter (EKF) for estimating the angular velocities. Given the angular velocity estimates from the EKF, the three ODE's for the linear velocity become algebraic, and the linear velocity can be calculated by numerical integration. Thus, we do not need direct measurements of the linear velocity to provide observability, and the technique is mathematically feasible. Using a simulation example, we show that the estimator adds value over the numerical ODE solver in the presence of measurement noise. Calculating the velocities in the

  17. Non-consent to a wrist-worn accelerometer in older adults: the role of socio-demographic, behavioural and health factors.

    Directory of Open Access Journals (Sweden)

    Maliheh Hassani

    Full Text Available Accelerometers, initially waist-worn but increasingly wrist-worn, are used to assess physical activity free from reporting-bias. However, its acceptability by study participants is unclear. Our objective is to assess factors associated with non-consent to a wrist-mounted accelerometer in older adults.Data are from 4880 Whitehall II study participants (1328 women, age range = 60-83, requested to wear a wrist-worn accelerometer 24 h every day for 9 days in 2012/13. Sociodemographic, behavioral, and health-related factors were assessed by questionnaire and weight, height, blood pressure, cognitive and motor function were measured during a clinical examination.210 participants had contraindications and 388 (8.3% of the remaining 4670 participants did not consent. Women, participants reporting less physical activity and less favorable general health were more likely not to consent. Among the clinical measures, cognitive impairment (Odds Ratio = 2.21, 95% confidence interval: 1.22-4.00 and slow walking speed (Odds Ratio = 1.38, 95% confidence interval: 1.02-1.86 were associated with higher odds of non-consent.The rate of non-consent in our study of older adults was low. However, key markers of poor health at older ages were associated with non-consent, suggesting some selection bias in the accelerometer data.

  18. Predicting daily eating activity of dairy cows from 3D accelerometer data and RFID signals by use of a random forests model

    DEFF Research Database (Denmark)

    Foldager, Leslie; Munksgaard, Lene; Trénel, Philipp;

    2015-01-01

    /logger combinations and synchronised with video recordings at the Danish Cattle Research Centre (DKC). The sensor recorded 3D accelerometer data and radio frequency identification (RFID) signals for positioning of the cow at the feed bunk. Video observations from 21 to 48 hours per cow/logger combination were...

  19. Detection of Gait and Postures Using a Miniaturized Triaxial Accelerometer-Based System : Accuracy in Patients With Mild to Moderate Parkinson's Disease

    NARCIS (Netherlands)

    Dijkstra, Baukje; Kamsma, Ype P.; Zijlstra, Wiebren

    2010-01-01

    Objective: To examine whether gait and postures can accurately be detected with a single small body-fixed device in patients with mild to moderate Parkinson's disease (PD). Design: Results of a triaxial accelerometer-based method were evaluated against video observation scores (criterion measure). S

  20. Identification of Prey Captures in Australian Fur Seals (Arctocephalus pusillus doriferus Using Head-Mounted Accelerometers: Field Validation with Animal-Borne Video Cameras.

    Directory of Open Access Journals (Sweden)

    Beth L Volpov

    Full Text Available This study investigated prey captures in free-ranging adult female Australian fur seals (Arctocephalus pusillus doriferus using head-mounted 3-axis accelerometers and animal-borne video cameras. Acceleration data was used to identify individual attempted prey captures (APC, and video data were used to independently verify APC and prey types. Results demonstrated that head-mounted accelerometers could detect individual APC but were unable to distinguish among prey types (fish, cephalopod, stingray or between successful captures and unsuccessful capture attempts. Mean detection rate (true positive rate on individual animals in the testing subset ranged from 67-100%, and mean detection on the testing subset averaged across 4 animals ranged from 82-97%. Mean False positive (FP rate ranged from 15-67% individually in the testing subset, and 26-59% averaged across 4 animals. Surge and sway had significantly greater detection rates, but also conversely greater FP rates compared to heave. Video data also indicated that some head movements recorded by the accelerometers were unrelated to APC and that a peak in acceleration variance did not always equate to an individual prey item. The results of the present study indicate that head-mounted accelerometers provide a complementary tool for investigating foraging behaviour in pinnipeds, but that detection and FP correction factors need to be applied for reliable field application.

  1. Adaptive recognition and correction of baseline shifts from collocated GPS and accelerometer using two phases Kalman filter

    Science.gov (United States)

    Tu, Rui; Wang, Rongjiang; Walter, Thomas R.; Diao, FaQi

    2014-11-01

    The real-time recognition and precise correction of baseline shifts in strong-motion records is a critical issue for GPS and accelerometer combined processing. This paper proposes a method to adaptively recognize and correct baseline shifts in strong-motion records by utilizing GPS measurements using two phases Kalman filter. By defining four kinds of learning statistics and criteria, the time series of estimated baseline shifts can be divided into four time intervals: initialization, static, transient and permanent. During the time interval in which the transient baseline shift is recognized, the dynamic noise of the Kalman filter system and the length of the baseline shifts estimation window are adaptively adjusted to yield a robust integration solution. The validations from an experimental and real datasets show that acceleration baseline shifts can be precisely recognized and corrected, thus, the combined system adaptively adjusted the estimation strategy to get a more robust solution.

  2. Gait event detection using linear accelerometers or angular velocity transducers in able-bodied and spinal-cord injured individuals.

    Science.gov (United States)

    Jasiewicz, Jan M; Allum, John H J; Middleton, James W; Barriskill, Andrew; Condie, Peter; Purcell, Brendan; Li, Raymond Che Tin

    2006-12-01

    We report on three different methods of gait event detection (toe-off and heel strike) using miniature linear accelerometers and angular velocity transducers in comparison to using standard pressure-sensitive foot switches. Detection was performed with normal and spinal-cord injured subjects. The detection of end contact (EC), normally toe-off, and initial contact (IC) normally, heel strike was based on either foot linear accelerations or foot sagittal angular velocity or shank sagittal angular velocity. The results showed that all three methods were as accurate as foot switches in estimating times of IC and EC for normal gait patterns. In spinal-cord injured subjects, shank angular velocity was significantly less accurate (p<0.02). We conclude that detection based on foot linear accelerations or foot angular velocity can correctly identify the timing of IC and EC events in both normal and spinal-cord injured subjects. PMID:16500102

  3. Design and test of a novel accelerometer made-up of an optical-fiber embedded within a polymer resin

    Directory of Open Access Journals (Sweden)

    Tihon Pierre

    2015-01-01

    Full Text Available This paper presents a transducer for an optical-fiber accelerometer based on a polarization analysis. The transducer is made up of a fiber section embedded within a resin placed between two metallic pieces. Due to the acceleration, the resin is crushed between the metallic pieces, deforming the fiber section and inducing birefringence in the latter. This birefringence modifies the light polarization state, which can be used as an acceleration measurement. The sensor characteristics (sensitivity and resonance frequency are numerically and experimentally determined. Sine accelerations at 120 Hz with amplitudes going from 5 m/s2 to 13 m/s2 have been successfully measured. The resonance frequency for the transducer crushing mode is above 5000 Hz, but low-frequency vibration modes exist, disturbing the measurements.

  4. Improving the Responses of Several Accelerometers Used in a Car Under Performance Tests by Using Kalman Filtering

    Directory of Open Access Journals (Sweden)

    Wilmar Hernández

    2001-06-01

    Full Text Available In this paper a Kalman filter is used to cancel noise and interference contained in two accelerometers embedded in a car under performance tests. Here, the frequency bands of the signals of interest and their noise (deterministic as well as stochastic are not strongly mixed with each other but it is very difficult to diminish the noise by using the classical approach to filtering. This reason, among others, justifies the necessity of the application of optimal filtering; and the Kalman filtering application allowed us to obtain optimal results (in the minimum mean-square sense and signal-to-noise ratio improvements higher than 30 dB were achieved. The experimental results demonstrate the importance of using both analog signal conditioning and digital signal processing when dealing with signals corrupted by noise.

  5. Use of accelerometers as an ergonomic assessment method for arm acceleration-a large-scale field trial.

    Science.gov (United States)

    Estill, C F; MacDonald, L A; Wenzl, T B; Petersen, M R

    2000-09-01

    Ergonomists need easy-to-use, quantitative job evaluation methods to assess risk factors for upper extremity work-related musculoskeletal disorders in field-based epidemiology studies. One device that may provide an objective measure of exposure to arm acceleration is a wrist-worn accelerometer or activity monitor. A field trial was conducted to evaluate the performance of a single-axis accelerometer using an industrial population (n=158) known to have diverse upper limb motion characteristics. The second phase of the field trial involved an examination of the relationship between more traditional observation-based ergonomic exposure measures and the monitor output among a group of assembly-line production employees (n=48) performing work tasks with highly stereotypic upper limb motion patterns. As expected, the linear acceleration data obtained from the activity monitor showed statistically significant differences between three occupational groups known observationally to have different upper limb motion requirements. Among the assembly-line production employees who performed different short-cycle assembly work tasks, statistically significant differences were also observed. Several observation-based ergonomic exposure measures were found to explain differences in the acceleration measure among the production employees who performed different jobs: hand and arm motion speed, use of the hand as a hammer, and, negatively, resisting forearm rotation from the torque of a power tool. The activity monitors were found to be easy to use and non-intrusive, and to be able to distinguish arm acceleration among groups with diverse upper limb motion characteristics as well as between different assembly job tasks where arm monitors were performed repeatedly at a fixed rate.

  6. Estimation of daily energy expenditure in pregnant and non-pregnant women using a wrist-worn tri-axial accelerometer.

    Directory of Open Access Journals (Sweden)

    Vincent T van Hees

    Full Text Available BACKGROUND: Few studies have compared the validity of objective measures of physical activity energy expenditure (PAEE in pregnant and non-pregnant women. PAEE is commonly estimated with accelerometers attached to the hip or waist, but little is known about the validity and participant acceptability of wrist attachment. The objectives of the current study were to assess the validity of a simple summary measure derived from a wrist-worn accelerometer (GENEA, Unilever Discover, UK to estimate PAEE in pregnant and non-pregnant women, and to evaluate participant acceptability. METHODS: Non-pregnant (N = 73 and pregnant (N = 35 Swedish women (aged 20-35 yrs wore the accelerometer on their wrist for 10 days during which total energy expenditure (TEE was assessed using doubly-labelled water. PAEE was calculated as 0.9×TEE-REE. British participants (N = 99; aged 22-65 yrs wore accelerometers on their non-dominant wrist and hip for seven days and were asked to score the acceptability of monitor placement (scored 1 [least] through 10 [most] acceptable. RESULTS: There was no significant correlation between body weight and PAEE. In non-pregnant women, acceleration explained 24% of the variation in PAEE, which decreased to 19% in leave-one-out cross-validation. In pregnant women, acceleration explained 11% of the variation in PAEE, which was not significant in leave-one-out cross-validation. Median (IQR acceptability of wrist and hip placement was 9(8-10 and 9(7-10, respectively; there was a within-individual difference of 0.47 (p<.001. CONCLUSIONS: A simple summary measure derived from a wrist-worn tri-axial accelerometer adds significantly to the prediction of energy expenditure in non-pregnant women and is scored acceptable by participants.

  7. Does a waist-worn accelerometer capture intra- and inter-person variation in walking behavior among persons with multiple sclerosis?

    Science.gov (United States)

    Motl, Robert W.; Sosnoff, Jacob J.; Dlugonski, Deirdre; Suh, Yoojin; Goldman, Myla

    2011-01-01

    The valid application of accelerometry and interpretation of its output (i.e., counts per unit time) for the measurement of walking behavior in persons with multiple sclerosis (MS) rests upon multiple untested assumptions. This study tested the assumption that a waist-worn accelerometer should capture the intra- and inter-person variation in walking behavior. Twenty-four participants with a neurologist-confirmed diagnosis of MS and who were ambulatory with minimal assistance undertook three 6-min periods of over-ground walking that involved comfortable (CWS) and then slower (SWS) and faster (FWS) walking speeds while wearing ActiGraph, model 7164, accelerometers around the waist and ankle. The experimental manipulation of walking was successful such that the CWS was 76.7 ± 13.0 m/min (range = 55.6–105.14), whereas the SWS and FWS were 64.3 ± 12.3 m/min (range = 44.5–90.1) and 89.1 ± 13.8 m/min (range = 60.9–116.4), respectively. Movement counts from the waist and ankle-worn accelerometer were strongly associated with the manipulation of speed, but the association was stronger for the waist than ankle based on both eta-squared estimates (η2 values = .78 and .46) and the average squared multiple correlations from individual regression analyses (R2 values = .97 ± .04 and .88 ± .21). The bivariate correlation between movement counts from the waist-worn accelerometer and speed of walking (r = .823, p = .001) was large in magnitude and significantly different (z = 3.22, p = .001) from that between movement counts from the ankle-worn unit and walking speed (r = .549, p = .001). This study provides novel evidence that an accelerometer worn around the waist captures intra- and inter-person variation in over-ground walking behavior in those with MS. PMID:20875952

  8. Performance analysis on captive silicon micro-accelerometer system%电容式硅微加速度计系统的性能分析

    Institute of Scientific and Technical Information of China (English)

    吉训生; 王寿荣; 许宜申; 盛平

    2006-01-01

    The operational principle and the lumped parameters model of capacitive micro-accelerometer are introduced. The equivalent stiffness of different directions of the accelerometer is given. From the point of view of energy and mechanics, expressions of some key parameters, such as the damping, sensitivity, resolution of the accelerometer, are derived. The accelerometer noise behavior of mechanical-thermal noise in the open-loop system, along with the dynamic range of the open-loop system and closed-loop system is analyzed. The result is that the noise of the capacitive micro accelerometer is dominated by the magnitude of mechanical-thermal noise. At the same time, the magnitude of mechanical-thermal noise depends on the temperature and magnitude of mechanical damp. The result of the measurement from the implemented closed-loop micro-accelerometer system shows that the resolution is the level of mg, and the measurement range is from -50g to 50g.%介绍了微加速度计的工作原理,得出了不同方向上的加速度计的等效刚度.基于加速度计的集总模型分析,从能量和运动角度推导得出了加速度计的等效质量、精度和灵敏度的具体表达形式.从力学观点,总结了加速度计阻尼的影响因素.对开环和闭环加速度计系统的机械-热噪声的特性和它们各自检测的动态范围进行研究后发现,电容式微加速度计的噪声主要由机械热噪声决定,并取决于加速度计系统的温度和阻尼.对闭环加速度计系统的测量结果表明,系统的精度可以达到mg数量级,量程为±50g的范围.

  9. Walk Score, Transportation Mode Choice, and Walking Among French Adults: A GPS, Accelerometer, and Mobility Survey Study

    Science.gov (United States)

    Duncan, Dustin T.; Méline, Julie; Kestens, Yan; Day, Kristen; Elbel, Brian; Trasande, Leonardo; Chaix, Basile

    2016-01-01

    Background: Few studies have used GPS data to analyze the relationship between Walk Score, transportation choice and walking. Additionally, the influence of Walk Score is understudied using trips rather than individuals as statistical units. The purpose of this study is to examine associations at the trip level between Walk Score, transportation mode choice, and walking among Paris adults who were tracked with GPS receivers and accelerometers in the RECORD GPS Study. Methods: In the RECORD GPS Study, 227 participants were tracked during seven days with GPS receivers and accelerometers. Participants were also surveyed with a GPS-based web mapping application on their activities and transportation modes for all trips (6969 trips). Walk Score, which calculates neighborhood walkability, was assessed for each origin and destination of every trip. Multilevel logistic and linear regression analyses were conducted to estimate associations between Walk Score and walking in the trip or accelerometry-assessed number of steps for each trip, after adjustment for individual/neighborhood characteristics. Results: The mean overall Walk Scores for trip origins were 87.1 (SD = 14.4) and for trip destinations 87.1 (SD = 14.5). In adjusted trip-level associations between Walk Score and walking only in the trip, we found that a walkable neighborhood in the trip origin and trip destination was associated with increased odds of walking in the trip assessed in the survey. The odds of only walking in the trip were 3.48 (95% CI: 2.73 to 4.44) times higher when the Walk Score for the trip origin was “Walker’s Paradise” compared to less walkable neighborhoods (Very/Car-Dependent or Somewhat Walkable), with an identical independent effect of trip destination Walk Score on walking. The number of steps per 10 min (as assessed with accelerometry) was cumulatively higher for trips both originating and ending in walkable neighborhoods (i.e., “Very Walkable”). Conclusions: Walkable

  10. French Pregnancy Physical Activity Questionnaire compared with an accelerometer cut point to classify physical activity among pregnant obese women.

    Directory of Open Access Journals (Sweden)

    Nadia Chandonnet

    Full Text Available Given the high risk for inactivity during pregnancy in obese women, validated questionnaires for physical activity (PA assessment in this specific population is required before evaluating the effect of PA on perinatal outcomes. No questionnaire was validated in pregnant obese women. The Pregnancy Physical Activity Questionnaire (PPAQ has been designed based on activities reported during pregnancy and validated in pregnant women. We translated the PPAQ to French and assessed reliability and accuracy of this French version among pregnant obese women. In this cross-sectional study, pregnant obese women were evenly recruited at the end of each trimester of pregnancy. They completed the PPAQ twice, with an interval of 7 days in-between, to recall PA of the last three months. Between PPAQ assessments, participants wore an accelerometer (Actigraph GT1M during 7 consecutive days. Fourty-nine (49 pregnant obese women (29.8±4.2 yrs, 34.7±5.1 kg x m(-2 participated to the study. The intraclass correlation coefficients (ICCs between the two PPAQ assessments were 0.90 for total activity, 0.86 for light and for moderate intensity, and 0.81 for vigorous intensity activities. It ranged from 0.59 for "Transportation" to 0.89 for "Household and Caregiving" activities. Spearman correlation coefficients (SCCs between the PPAQ and the Matthews' cut point used to classify an activity of moderate and above intensity were 0.50 for total activity, 0.25 for vigorous intensity and 0.40 for moderate intensity. The correlations between the PPAQ and the accelerometer counts were 0.58 for total activity, 0.39 for vigorous intensity and 0.49 for moderate intensity. The highest SCCs were for "Occupation" and "Household and Caregiving" activities. Comparisons with other standard cutpoints were presented in files S1, S2, S3, S4, S5, S6, S7. The PPAQ is reliable and moderately accurate for the measure of PA of various intensities and types among pregnant obese women.

  11. Population-referenced percentiles for waist-worn accelerometer-derived total activity counts in U.S. youth: 2003 - 2006 NHANES.

    Directory of Open Access Journals (Sweden)

    Dana L Wolff-Hughes

    Full Text Available The total activity volume performed is an overall measure that takes into account the frequency, intensity, and duration of activities performed. The importance of considering total activity volume is shown by recent studies indicating that light physical activity (LPA and intermittent moderate-to-vigorous physical activity (MVPA have health benefits. Accelerometer-derived total activity counts (TAC per day from a waist-worn accelerometer can serve as a proxy for an individual's total activity volume. The purpose of this study was to develop age- and gender-specific percentiles for daily TAC, minutes of MVPA, and minutes of LPA in U.S. youth ages 6 - 19 y.Data from the 2003 - 2006 NHANES waist-worn accelerometer component were used in this analysis. The sample was composed of youth aged 6 - 19 years with at least 4 d of ≥ 10 hours of accelerometer wear time (N = 3698. MVPA was defined using age specific cutpoints as the total number of minutes at ≥4 metabolic equivalents (METs for youth 6 - 17 y or minutes with ≥2020 counts for youth 18 - 19 y. LPA was defined as the total number of minutes between 100 counts and the MVPA threshold. TAC/d, MVPA, and LPA were averaged across all valid days.For males in the 50th percentile, the median activity level was 441,431 TAC/d, with 53 min/d of MVPA and 368 min/d of LPA. The median level of activity for females was 234,322 TAC/d, with 32 min/d of MVPA and 355 min/d of LPA.Population referenced TAC/d percentiles for U.S. youth ages 6-19 y provide a novel means of characterizing the total activity volume performed by children and adolescents.

  12. The validity of the non-exercise activity thermogenesis questionnaire evaluated by objectively measured daily physical activity by the triaxial accelerometer

    OpenAIRE

    Hamasaki, Hidetaka; Yanai, Hidekatsu; Kakei, Masafumi; Noda, Mitsuhiko; Ezaki, Osamu

    2014-01-01

    Background Physical inactivity is a major cardiovascular risk factor. Recently, we showed that non-exercise activity thermogenesis (NEAT) assessed by the self-reported questionnaire is favorably associated with metabolic risks in patients with type 2 diabetes. The purpose of the present study was to examine the validity of the questionnaire by comparing with objectively measured daily physical activity (PA) by using the triaxial accelerometer. Methods Daily physical activity level (PAL) of 51...

  13. Does a waist-worn accelerometer capture intra- and inter-person variation in walking behavior among persons with multiple sclerosis?

    OpenAIRE

    Motl, Robert W.; Sosnoff, Jacob J.; Dlugonski, Deirdre; Suh, Yoojin; Goldman, Myla

    2010-01-01

    The valid application of accelerometry and interpretation of its output (i.e., counts per unit time) for the measurement of walking behavior in persons with multiple sclerosis (MS) rests upon multiple untested assumptions. This study tested the assumption that a waist-worn accelerometer should capture the intra- and inter-person variation in walking behavior. Twenty-four participants with a neurologist-confirmed diagnosis of MS and who were ambulatory with minimal assistance undertook three 6...

  14. Validity and Reliability of Gait and Postural Control Analysis Using the Tri-axial Accelerometer of the iPod Touch.

    Science.gov (United States)

    Kosse, Nienke M; Caljouw, Simone; Vervoort, Danique; Vuillerme, Nicolas; Lamoth, Claudine J C

    2015-08-01

    Accelerometer-based assessments can identify elderly with an increased fall risk and monitor interventions. Smart devices, like the iPod Touch, with built-in accelerometers are promising for clinical gait and posture assessments due to easy use and cost-effectiveness. The aim of the present study was to establish the validity and reliability of the iPod Touch for gait and posture assessment. Sixty healthy participants (aged 18-75 years) were measured with an iPod Touch and stand-alone accelerometer while they walked under single- and dual-task conditions, and while standing in parallel and semi-tandem stance with eyes open, eyes closed and when performing a dual task. Cross-correlation values (CCV) showed high correspondence of anterior-posterior and medio-lateral signal patterns (CCV's ≥ 0.88). Validity of gait parameters (foot contacts, index of harmonicity, and amplitude variability) and standing posture parameters [root mean square of accelerations, median power frequency (MPF) and sway area] as indicated by intra-class correlation (ICC) was high (ICC = 0.85-0.99) and test-retest reliability was good (ICC = 0.81-0.97), except for MPF (ICC = 0.59-0.87). Overall, the iPod Touch obtained valid and reliable measures of gait and postural control in healthy adults of all ages under different conditions. Additionally, smart devices have the potential to be used for clinical gait and posture assessments.

  15. Comparison between low-cost and traditional MEMS accelerometers: a case study from the M7.1 Darfield, New Zealand, aftershock deployment

    Directory of Open Access Journals (Sweden)

    Angela Chung

    2011-06-01

    Full Text Available Recent advances in micro-electro-mechanical systems (MEMS sensing and distributed computing techniques have enabled the development of low-cost, rapidly deployed dense seismic networks. The Quake-Catcher Network (QCN uses triaxial MEMS accelerometers installed in homes and businesses to record moderate to large earthquakes. Real-time accelerations are monitored and information is transferred to a central server using open-source, distributed computing software installed on participating computers. Following the September 3, 2010, Mw 7.1 Darfield, New Zealand, earthquake, 192 QCN stations were installed in a dense array in the city of Christchurch and the surrounding region to record the on-going aftershock sequence. Here, we compare the ground motions recorded by QCN accelerometers with GeoNet strong-motion instruments to verify whether low-cost MEMS accelerometers can provide reliable ground-motion information in network-scale deployments. We find that observed PGA and PGV amplitudes and RMS scatter are comparable between the GeoNet and QCN observations. Closely spaced stations provide similar acceleration, velocity, and displacement time series and computed response spectra are also highly correlated, with correlation coefficients above 0.94.

  16. Noise analysis and characterization of a full differential CMOS interface circuit for capacitive closed-loop micro-accelerometer

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao-wei; LI Hai-tao; YIN Liang; CHEN Wei-ping; SUO Chun-guang; ZHOU Zhi-ping

    2010-01-01

    To achieve a high precision capacitive closed-loop micro-accelerometer,a full differential CMOS based on switched-capacitor circuit was presented in this paper as the sensor interface circuit.This circuit consists of a balance-bridge module,a charge sensitive amplifier,a correlated-double-sampling module,and a logic timing control module.A special two-path feedback circuit configuration was given to improve the system linearity.The quantitative analysis of error voltage and noise shows that there is tradeoff around circuit's noise,speed and accuracy.A detailed design method was given for this tradeoff.The noise performance optimized circuit has a noise root spectral density of 1.0 μV/√Hz,equivalent to rms noise root spectral density of1.63 μg/√Hz.Therefore,the sensor' s Brown noise becomes the main noise source in this design.This circuit is designed with 0.5 μm n-well CMOS process.Under a ± 5 V supply,the Hspice simulation shows that the system sensitivity achieves 0.616 V/g,the system offset is as low as 1.456 mV,the non-linearity is below0.03%,and the system linear range achieves ±5 g.

  17. Large-scale traveling atmospheric disturbances (LSTADs) in the thermosphere inferred from CHAMP, GRACE, and SETA accelerometer data

    Science.gov (United States)

    Bruinsma, Sean L.; Forbes, Jeffrey M.

    2010-08-01

    Densities derived from accelerometer measurements on the GRACE, CHAMP, and Air Force/SETA satellites near 490, 390, and 220 km, respectively, are used to elucidate global-scale characteristics of traveling atmospheric disturbances (TADs). Several characteristics elucidated in numerical simulations are confirmed in this study, namely: (1) propagation speeds increase from the lower thermosphere to the upper thermosphere; (2) propagation to the equator and even into the opposite hemisphere can occur; (3) greater attenuation of TADs occurs during daytime and at higher levels of solar activity (i.e., more wave activity during nighttime and solar minimum), presumably due to the greater influence of ion drag. In addition, we find that the occurrence of significant TAD activity emanating from the auroral regions does not reflect a clear relation with the level of planetary magnetic activity as measured by Kp. There is also evidence of waves originating in the tropics, presumably due to convective sources; to some extent this may contribute to the Kp and solar flux relationships noted above. Further elucidation of local time, season, and altitude dependences of TAD propagation characteristics may be forthcoming from density measurements from the GOCE and Swarm missions.

  18. Rapid earthquake characterization using MEMS accelerometers and volunteer hosts following the M 7.2 Darfield, New Zealand, Earthquake

    Science.gov (United States)

    Lawrence, J. F.; Cochran, E.S.; Chung, A.; Kaiser, A.; Christensen, C. M.; Allen, R.; Baker, J.W.; Fry, B.; Heaton, T.; Kilb, Debi; Kohler, M.D.; Taufer, M.

    2014-01-01

    We test the feasibility of rapidly detecting and characterizing earthquakes with the Quake‐Catcher Network (QCN) that connects low‐cost microelectromechanical systems accelerometers to a network of volunteer‐owned, Internet‐connected computers. Following the 3 September 2010 M 7.2 Darfield, New Zealand, earthquake we installed over 180 QCN sensors in the Christchurch region to record the aftershock sequence. The sensors are monitored continuously by the host computer and send trigger reports to the central server. The central server correlates incoming triggers to detect when an earthquake has occurred. The location and magnitude are then rapidly estimated from a minimal set of received ground‐motion parameters. Full seismic time series are typically not retrieved for tens of minutes or even hours after an event. We benchmark the QCN real‐time detection performance against the GNS Science GeoNet earthquake catalog. Under normal network operations, QCN detects and characterizes earthquakes within 9.1 s of the earthquake rupture and determines the magnitude within 1 magnitude unit of that reported in the GNS catalog for 90% of the detections.

  19. Detecting Intra-Fraction Motion in Patients Undergoing Radiation Treatment Using a Low-Cost Wireless Accelerometer

    Directory of Open Access Journals (Sweden)

    Joel J. P. C. Rodrigues

    2009-08-01

    Full Text Available The utility of a novel, high-precision, non-intrusive, wireless, accelerometerbased patient orientation monitoring system (APOMS in determining orientation change in patients undergoing radiation treatment is reported here. Using this system a small wireless accelerometer sensor is placed on a patient’s skin, broadcasting its orientation to the receiving station connected to a PC in the control area. A threshold-based algorithm is developed to identify the exact amount of the patient’s head orientation change. Through real-time measurements, an audible alarm can alert the radiation therapist if the user-defined orientation threshold is violated. Our results indicate that, in spite of its low-cost and simplicity, the APOMS is highly sensitive and offers accurate measurements. Furthermore, the APOMS is patient friendly, vendor neutral, and requires minimal user training. The versatile architecture of the APOMS makes it potentially suitable for variety of applications, including study of correlation between external and internal markers during Image-Guided Radiation Therapy (IGRT, with no major changes in hardware setup or algorithm.

  20. VLC-Based Positioning System for an Indoor Environment Using an Image Sensor and an Accelerometer Sensor.

    Science.gov (United States)

    Huynh, Phat; Yoo, Myungsik

    2016-01-01

    Recently, it is believed that lighting and communication technologies are being replaced by high power LEDs, which are core parts of the visible light communication (VLC) system. In this paper, by taking advantages of VLC, we propose a novel design for an indoor positioning system using LEDs, an image sensor (IS) and an accelerometer sensor (AS) from mobile devices. The proposed algorithm, which provides a high precision indoor position, consists of four LEDs mounted on the ceiling transmitting their own three-dimensional (3D) world coordinates and an IS at an unknown position receiving and demodulating the signals. Based on the 3D world coordinates and the 2D image coordinate of LEDs, the position of the mobile device is determined. Compared to existing algorithms, the proposed algorithm only requires one IS. In addition, by using an AS, the mobile device is allowed to have arbitrary orientation. Last but not least, a mechanism for reducing the image sensor noise is proposed to further improve the accuracy of the positioning algorithm. A simulation is conducted to verify the performance of the proposed algorithm. PMID:27240383