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Sample records for accelerometers

  1. Piezoelectric Accelerometers Development

    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...... 8325 are below 6%. It is proved that the specifications of the accelerometer can be effectively predicted using the FE method, especially when modifications of the accelerometer are required. The development process of piezoelectric accelerometers in Brüel & Kjær is becoming more efficient...

  2. Piezoelectric Accelerometers Development

    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...

  3. A microchip optomechanical accelerometer

    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 ...

  4. Superconducting Rebalance Accelerometer

    Torti, R. P.; Gerver, M.; Leary, K. J.; Jagannathan, S.; Dozer, D. M.

    1996-01-01

    A multi-axis accelerometer which utilizes a magnetically-suspended, high-TC proof mass is under development. The design and performance of a single axis device which is stabilized actively in the axial direction but which utilizes ring magnets for passive radial stabilization is discussed. The design of a full six degree-of-freedom device version is also described.

  5. A microchip optomechanical accelerometer

    Krause, Alexander G.; Winger, Martin; 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 a...

  6. Capacitive Position Sensor For Accelerometer

    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.

  7. Piezoelectric accelerometers with integral electronics

    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

  8. Optomechanical reference accelerometer

    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.

  9. Equating accelerometer estimates among youth

    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...

  10. Accelerometer for mobile robot positioning

    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...

  11. Application of MEMS accelerometer to geophysics

    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...

  12. Accelerometer and strain gage evaluation

    This document describes the method developed by Sandia National Laboratories (SNL) to evaluate transducer used in the design certification testing of nuclear material shipping packages. This testing project was performed by SNL for the Office of Civilian Radioactive Waste Management (OCRWM). This evaluation is based on the results of tests conducted to measure ruggedness, failure frequency, repeatability, and manufacturers' calibration data under both field and laboratory conditions. The results of these tests are provided and discussed. The transducer were selected for testing by surveying cask contractors and testing facilities. Important insights relating to operational characteristics of accelerometer types were gained during field testing. 11 refs., 105 figs., 16 tabs

  13. A New Annular Shear Piezoelectric Accelerometer

    Liu, Bin; Kriegbaum, B.

    2000-01-01

    This paper describes the construction and performance of a recently introduced Annular Shear piezoelectric accelerometer, Type 4511. The design has insulated and double-shielded case. The accelerometer housing is made of stainless steel, AISI 316L. Piezoceramic PZ23 is used. The seismic mass...

  14. High Temperature Endurable Fiber Optic Accelerometer

    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

    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.

  16. Hybridizing matter-wave and classical accelerometers

    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.

  17. Step Counting Using Smartphone-Based Accelerometer

    Ms. Najme Zehra Naqvi

    2012-05-01

    Full Text Available This paper presents a method for counting the number of steps taken by a user, while walking at any variable speed, using smartphone-based accelerometer. For this purpose, the steps are detected based on a relation between frequency of step, which varies inversely with speed of motion, and the magnitude of accelerometer signal. The pattern of the forward acceleration was observed to arrive at the final relation.

  18. A mechanical model of the smartphone's accelerometer

    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.

  19. High Temperature Endurable Fiber Optic Accelerometer

    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...

  20. The Development of Piezoelectric Accelerometers Using Finite Elemen Analysis

    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 modeling...... 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...

  1. The Development of Piezoelectric Accelerometers Using Finite Element Analysis

    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 modeling...... 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. Detecting gunshots using wearable accelerometers.

    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.

  3. Optomechanical accelerometers and gravity gradiometers

    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.

  4. ISA accelerometer and Lunar science

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

    In recent years the Moon has become again a target for exploration activities, as shown by many missions, performed, ongoing or foreseen. The reasons for this new wave are manifold. The knowledge of formation and evolution of the Moon to its current state is important in order to trace the overall history of the 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 for testing gravitation theories. All these topics are providing stimulus and inspirations for new experiments: in fact a wide variety of them has been proposed to be conducted on the lunar surface. ISA (Italian Spring Accelerometer) can provide an important tool for lunar studies. Thanks to its design it works on-ground with the same configuration developed for in-orbit applications. It can therefore be used onboard a spacecraft, as a support to a radio science mission, and on the surface of the Moon, as a seismometer. This second option in particular has been the subject of preliminary studies and has been proposed as a candidate to be hosted on NASA ILN (International Lunar Network) and ESA First Lunar Lander. ISA-S (ISA-Seismometer) has a very high sensitivity, which has already been demonstrated with long time periods of usage on Earth. It features also a wide bandwidth, extended towards the low frequencies. After a description of the instrument, its use in the context of landing missions will be described and discussed, giving emphasis on its integration with the other components of the systems.

  5. CHAMP Tracking and Accelerometer Data Analysis Results

    Lemoine, Frank G.; Luthcke, S. B.; Rowlands, D. D.; Pavlis, D. E.; Colombo, O. L.; Ray, Richard D.; Thompson, B.; Nerem, R. S.; Williams, Teresa A.; Smith, David E. (Technical Monitor)

    2002-01-01

    The CHAMP (Challenging Minisatellite Payload) mission's unique combination of sensors and orbit configuration will enable unprecedented improvements in modeling and understanding the Earth's static gravity field and its temporal variations. CHAMP is the first of two missions (GRACE (Gravity Recovery and Climate Experiment) to be launched in the later part of '01) that combine a new generation of GPS (Global Positioning System) receivers, a high precision three axis accelerometer, and star cameras for the precision attitude determination. In order to isolate the gravity signal for science investigations, it is necessary to perform a detailed reduction and analysis of the GPS and SLR tracking data in conjunction with the accelerometer and attitude data. Precision orbit determination based on the GPS and SLR (Satellite Laser Ranging) tracking data will isolate the orbit perturbations, while the accelerometer data will be used to distinguish the surface forces from those due to the geopotential (static, and time varying). In preparation for the CHAMP and GRACE missions, extensive modifications have been made to NASA/GSFC's GEODYN orbit determination software to enable the simultaneous reduction of spacecraft tracking (e.g. GPS and SLR), three axis accelerometer and precise attitude data. Several weeks of CHAMP tracking and accelerometer data have been analyzed and the results will be presented. Precision orbit determination analysis based on tracking data alone in addition to results based on the simultaneous reduction of tracking and accelerometer data will be discussed. Results from a calibration of the accelerometer will be presented along with the results from various orbit determination strategies. Gravity field modeling status and plans will be discussed.

  6. Sensitivity improvement techniques for micromechanical vibrating accelerometers

    Vtorushin Sergey

    2016-01-01

    Full Text Available The paper presents the problems of detecting a desired signal generated by micromechanical vibrating accelerometer. Three detection methods, namely frequency, amplitude and phase are considered in this paper. These methods are used in micromechanical vibrating accelerometers that incorporate a force sensitive element which transforms measured acceleration into the output signal. Investigations are carried out using the ANSYS finite element program and MATLAB/Simulink support package. Investigation results include the comparative analysis of the output signal characteristics obtained by the different detection methods.

  7. Finite Element Based Design and Optimization for Piezoelectric Accelerometers

    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...

  8. Dual Accelerometer Usage Strategy for Onboard Space Navigation

    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.

  9. Three-axis MEMS Accelerometer for Structural Inspection

    Barbin, E.; Koleda, A.; Nesterenko, T.; Vtorushin, S.

    2016-01-01

    Microelectromechanical system accelerometers are widely used for metrological measurements of acceleration, tilt, vibration, and shock in moving objects. The paper presents the analysis of MEMS accelerometer that can be used for the structural inspection. ANSYS Multiphysics platform is used to simulate the behavior of MEMS accelerometer by employing a finite element model and MATLAB/Simulink tools for modeling nonlinear dynamic systems.

  10. Piezoelectric Accelerometers Modification Based on the Finite Element Method

    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...

  11. Fabrication and characterization of a piezoelectric accelerometer

    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...

  12. Smartphone MEMS accelerometers and earthquake early warning

    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.

  13. Accurate Telescope Mount Positioning with MEMS Accelerometers

    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.

  14. Multi-Axis Accelerometer Calibration System

    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.

  15. Dark Matter Direct Detection with Accelerometers

    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.

  16. Dark matter direct detection with accelerometers

    Graham, Peter W.; Kaplan, David E.; Mardon, Jeremy; Rajendran, Surjeet; Terrano, William A.

    2016-04-01

    The mass of the dark matter particle is unknown, and may be as low as ˜1 0-22 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, equivalence-principle-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.

  17. MGRA: Motion Gesture Recognition via Accelerometer

    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.

  18. MGRA: Motion Gesture Recognition via Accelerometer.

    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

  19. Standing stability evaluation using a triaxial accelerometer

    Mayagoitia, Ruth E.; Lotters, Joost C.; Veltink, Peter H.

    1996-01-01

    A triaxial accelerometer is placed at the back of the subject at the height of the center of mass. Force plate data are collected simultaneously. Subjects stand in a comfortable position with eyes open, eyes closed and doing cognitive tasks; and with feet together with eyes open and closed. The cognitive tasks are: mathematical, auditory Stroop and memory. The force plate data are processed to obtain the center of pressure and from it the parameters of: mean radius, speed and frequency, and b...

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

    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 (<100 Hz) and such sensors should have large sensitivity and extremely low 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.

  1. Design and Implementation of a Micromechanical Silicon Resonant Accelerometer

    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.

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

    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.

  3. Measurement device for cmos-mems accelerometer

    Somasundaram, Namitha

    2014-01-01

    [ANGLÈS] This project reports the process of development of the Printed Circuit Board (PCB) - Zephyr for the experimental CMOS MEMS accelerometer testchip, Bailed II. The problem of capacitance mismatch at the input bridge is solved through a simple and innovative arrangement of resistors, jumpers and capacitors on the PCB. A filter is designed with the inductor capacitor pair to filter noise from the DC source. An amplifier with a gain of 10 is designed to amplify the output signals of the B...

  4. Real-time inclinometer using accelerometer MEMS

    Hanto, D; Hermanto, B; Puranto, P; Handoko, L T

    2011-01-01

    A preliminary design of inclinometer for real-time monitoring system of soil displacement is proposed. The system is developed using accelerometer sensor with microelectromechanical system (MEMS) device. The main apparatus consists of a single MEMS sensor attached to a solid pipe and stucked pependicularly far away below the soil surface. The system utilizes small fractions of electrical signals from MEMS sensor induced by the pipe inclination due to soil displacements below the surface. It is argued that the system is accurate enough to detect soil displacements responsible for landslides, and then realizes a simple and low cost landslide early warning system.

  5. Analysis of MEMS Accelerometer for Optimized Sensitivity

    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%.

  6. Studying and Modeling Vibration Transducers and Accelerometers

    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.

  7. Calibrating Accelerometers Using an Electromagnetic Launcher

    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.

  8. MEMS Accelerometer with Screen Printed Piezoelectric Thick Film

    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...

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

    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

  10. ACCELEROMETER BASED GESTURE CONTROLLED ROBOT USING ARDUINO

    SwarnaPrabha Jena

    2015-04-01

    Full Text Available Generally, robots are programmed to perform specific tasks which humans cannot. To increase the use of robots where conditions are not certain such as fire fighting or rescue operations, robots can be made which follow the instruction of human operator and perform the task. In this way decisions are taken according to the working conditions by the operator and the task is performed by the robots. Thus, we can use these robots to perform those tasks that may be harmful for humans. This paper describes about the gesture control robot which can be controlled by your normal hand gesture. It consists of mainly two parts, one is transmitter part and another is receiver part. The transmitter will transmit the signal according to the position of accelerometer and your hand gesture and the receiver will receive the signal and make the robot move in respective direction. Here, the program is designed by using Arduino IDE.

  11. A high performance, variable capacitance accelerometer

    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.

  12. Recent Results from CHAMP Tracking and Accelerometer Data Analysis

    Luthcke, S. B.; Rowlands, D. D.; Lemoine, F. G.; Nerem, R. S.; Thompson, B.; Pavlis, E.; Williams, T. A.; Colombo, O. L.; Chao, Benjamin F. (Technical Monitor)

    2002-01-01

    The CHAMP mission's unique combination of sensors and orbit configuration will enable unprecedented improvements in modeling and understanding the Earth's static gravity field and its temporal variations. CHAMP is the first of two missions (GRACE to be launched in the early part of 02') that combine a new generation of Global Positioning System (GPS) receivers, a high precision three-axis accelerometer, and star cameras for the precision attitude determination. In order to isolate the gravity signal for science investigations, it is necessary to perform a detailed reduction and analysis of the GPS and Satellite Laser Ranging (SLR) tracking data in conjunction with the accelerometer and attitude data. Precision orbit determination based on the GPS and SLR tracking data will isolate the orbit perturbations, while the accelerometer data will be used to distinguish the non-gravitational forces from those due to the geopotential (static, and time varying). In preparation for the CHAMP and GRACE missions, extensive modifications have been made to NASA/GSFC's GEODYN orbit determination software to enable the simultaneous reduction of spacecraft tracking (e.g. GPS and SLR), three-axis accelerometer and precise attitude data. Several weeks of CHAMP tracking and accelerometer data have been analyzed and the results will be presented. Precision orbit determination analysis based on tracking data alone in addition to results based on the simultaneous reduction of tracking and accelerometer data will be discussed. Results from a calibration of the accelerometer will be presented along with the results from various orbit determination strategies.

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

    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.

  14. Adaptive integrated navigation filtering based on accelerometer calibration

    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.

  15. High sensitivity accelerometers for high performance seismic attenuators

    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

  16. Accelerometers for Measuring Physical Activity Behavior in Indian Children

    Krishnaveni, G V; Mills, I C; Veena, S. R.; Wootton, S A; Wills, A K; Coakley, P. J.; Fisher, D. J.; Shobha, S.; Karat, S. C.; Fall, C H D

    2009-01-01

    Objective: To examine the validity of accelerometers for characterizing habitual physical activity patterns in Indian children.Design: Cohort study.Setting: Holdsworth Memorial Hospital, Mysore.Subjects: Children (N=103, mean age 6.6 years) selected from an ongoing birth cohort study.Methods: Physical activity was measured over 7 days using accelerometers (MTI Actigraph) and concurrent parent-maintained activity diaries. Actigraph counts per minute representing sedentary (

  17. Input-output stability for accelerometer control systems

    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.

  18. Intelligent seismic sensor with double three component MEMS accelerometers

    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.

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

    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%.

  20. Strong Motion Seismograph Based On MEMS Accelerometer

    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

  1. The ISA accelerometer and Lunar science

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

    2014-05-01

    In recent years the Moon has become again a target for exploration activities, as shown by many missions, performed, ongoing or foreseen. The reasons for this new wave are manifold. The knowledge of formation and evolution of the Moon to its 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 for testing gravitation theories. All these topics are providing stimulus and inspirations for new experiments: in fact a wide variety of them has been proposed to be conducted on the lunar surface. 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 can therefore be used onboard a spacecraft, as a support to a radio science mission, and on the surface of the Moon, as a seismometer. This second option in particular has been the subject of preliminary studies and has been proposed as a candidate to be hosted on NASA ILN (International Lunar Network) and ESA First Lunar Lander. ISA-S (ISA-Seismometer) has a very high sensitivity, which has already been demonstrated with long time periods of usage on Earth. After a description of the instrument, its use in the context of landing missions will be described and discussed, giving emphasis on its integration with the other components of the systems.

  2. One testing method of dynamic linearity of an accelerometer

    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.

  3. Prediction of Gap Asymmetry in Differential Micro Accelerometers

    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.

  4. One testing method of dynamic linearity of an accelerometer

    Lei Jing-Yu

    2015-01-01

    Full Text Available 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.

  5. Damage detection by mixed measurements using accelerometers and strain gages

    This work investigates the relationship between the FRFs (frequency response functions) measured by accelerometers and strain gages utilized widely for investigating structural performance. Modifying the GDM (global-deviation method), this study examines the possibility of damage detection in utilizing both sensors together. The experimental results on the mixed utilization of two sensors show that the SFRF (strain frequency response function) data measured by strain gages in the neighborhood of end supports are more practical in establishing the baseline curve than the DFRF (displacement frequency response function) data measured by accelerometers. It is shown that the modified GDM can be effectively utilized in detecting damage based on the mixed measurements of accelerometers and strain gages. (paper)

  6. An Electromagnetically Excited Silicon Nitride Beam Resonant Accelerometer

    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.

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

    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%.

  8. Validation of different accelerometers to determine mechanical loading in children

    Meyer, Ursina; Ernst, Dominique; Schott, Silvia; Riera, Claudia; Hattendorf, Jan; Romkes, Jacqueline; Granacher, Urs; Goepfert, Beat; Kriemler, Susi

    2015-01-01

    The purpose of this study was to assess the validity of accelerometers using force plates (i.e., ground reaction force (GRF)) during the performance of different tasks of daily physical activity in children. Thirteen children (10.1 (range 5.4–15.7) years, 3 girls) wore two accelerometers (ActiGraph GT3X+ (ACT), GENEA (GEN)) at the hip that provide raw acceleration signals at 100 Hz. Participants completed different tasks (walking, jogging, running, landings from boxes of different height, rop...

  9. An Improved SPICE Model for MEMS Based Capacitive Accelerometers

    C. Kavitha

    2013-05-01

    Full Text Available An improved electrical equivalent circuit for a capacitive MEMS accelerometer, incorporating temperature, pressure and squeezed film effects is reported. The circuit model corresponds to a single degree of freedom (SDOF vibrating system, including dominant micro physical mechanisms. Static, transient and frequency response analysis are carried out at temperature and pressure ranges of 100 K to 400 K and 30 to 3000 Pa respectively. The effect of these parameters on the resonance frequency, peak displacement and settling time of the accelerometer are determined. Simulations are performed using PSpice® circuit simulator.

  10. Adaptive integrated navigation filtering based on accelerometer calibration

    Qifan Zhou; Hai Zhang; Yanran Wang

    2012-01-01

    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 adap...

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

    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.

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

    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....

  13. Predicting human movement with multiple accelerometers using movelets

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

    2014-01-01

    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...

  14. Circular Piezoelectric Accelerometer for High Band Width Application

    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...

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

    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

  16. Design and Evaluation of Accelerometer based Motional Feedback

    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...

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

    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

  18. The MICROSTAR electrostatic accelerometer for the GRASP Mission

    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.

  19. Geometric anti-spring vertical accelerometers for seismic monitoring

    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

  20. A simple intensity modulation based fiber-optic accelerometer

    Guozhen, Yao; Yongqian, Li; Zhi, Yang

    2016-05-01

    A fiber-optic accelerometer with simple structure and high performance based on intensity modulation is proposed. Using only a length of single mode fiber compressed by a cantilever, the intensity of reflected light is modulated by the vibration acceleration applied to it. The effects of the fiber location, the dimension parameters of the cantilever on frequency response and sensitivity are investigated. The experimental results demonstrate that the accelerometer has a flat frequency response over a 4700 Hz bandwidth and a sensitivity of 21.24 mV/g with a cantilever dimension of 30 × 8 × 1.6 mm3 and a distance of 5 mm between the fiber location and the suspended cantilever end; the coefficient of determination is better than 0.999. In addition, the effect of temperature and the stability of the sensing system are investigated.

  1. Guidelines for Standardized Testing of Broadband Seismometers and Accelerometers

    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.

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

    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.

  3. DEPTracker – Sleep Pattern Tracking with Accelerometer Technology

    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...

  4. Fibre Bragg grating based accelerometer with extended bandwidth

    Basumallick, Nandini; Biswas, Palas; Chakraborty, Rajib; Chakraborty, Sushanta; Dasgupta, Kamal; Bandyopadhyay, Somnath

    2016-03-01

    We have shown experimentally that the operable bandwidth of a fibre Bragg grating (FBG) based accelerometer can be extended significantly, without compromising its sensitivity, using a post-signal processing technique which involves frequency domain weighting. It has been demonstrated that using the above technique acceleration can be correctly interpreted even when the operating frequency encroaches on the region where the frequency response of the sensor is non-uniform. Two different excitation signals, which we often encounter in structural health monitoring applications, e.g. (i) a signal composed of multi-frequency components and (ii) a sinusoidal excitation with a frequency sweep, have been considered in our experiment. The results obtained have been compared with a piezo accelerometer.

  5. An Improved Wavelet Correction for Zero Shifted Accelerometer Data

    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.

  6. An Improved SPICE Model for MEMS Based Capacitive Accelerometers

    C. Kavitha; M. Ganesh Madhan

    2013-01-01

    An improved electrical equivalent circuit for a capacitive MEMS accelerometer, incorporating temperature, pressure and squeezed film effects is reported. The circuit model corresponds to a single degree of freedom (SDOF) vibrating system, including dominant micro physical mechanisms. Static, transient and frequency response analysis are carried out at temperature and pressure ranges of 100 K to 400 K and 30 to 3000 Pa respectively. The effect of these parameters on the resonance frequency, pe...

  7. Analysis of animal accelerometer data using hidden Markov models

    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...

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

    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...

  9. Travel Behavior Characterization Using Raw Accelerometer Data Collected from Smartphones

    Ferrer López, Sheila; Ruiz Sánchez, Tomás

    2014-01-01

    In this paper, we compare different algorithms for the recognition of transportation modes based on features extracted from the accelerometer data. The performance and effectiveness of the transportation mode classifiers presented is evaluated and their accuracy is discussed. The data set used for training and testing algorithms was collected by a group of volunteers in the city of Valencia in 2013; an Android application designed for the recording of trips and transportation modes applicatio...

  10. Monitoring feeding behaviour of dairy cows using accelerometers

    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

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

    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.

  12. Optical Readout of Micro-Accelerometer Code Features

    Dickey, Fred M.; Holswade, Scott C.; Polosky, Marc A.; Shagam, Richard N.; Sullivan, Charles T.

    1999-07-08

    Micromachine accelerometers offer a way to enable critical functions only when a system encounters a particular acceleration environment. This paper describes the optical readout of a surface micromachine accelerometer containing a unique 24-bit code. The readout uses waveguide-based optics, which are implemented as a photonic integrated circuit (PIC). The PIC is flip-chip bonded over the micromachine, for a compact package. The shuttle moves 500 {micro}m during readout, and each code element is 17 {micro}m wide. The particular readout scheme makes use of backscattered radiation from etched features in the accelerometer shuttle. The features are etched to create corner reflectors that return radiation back toward the source for a one bit. For a zero bit, the shuttle is not etched, and the radiation scatters forward, away from the detector. This arrangement provides a large signal difference between a one and zero signal, since the zero signal returns virtually no signal to the detector. It is thus superior to schemes that interrogate the code vertically, which have a limited contrast between a one and a zero. Experimental results are presented for mock shuttle features etched into a silicon substrate. To simulate the shuttle moving under a fixed PIC, a commercially available waveguide source was scanned over the mock code.

  13. Denoising and Trend Terms Elimination Algorithm of Accelerometer Signals

    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.

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

    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.

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

    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.

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

    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

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

    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 ...

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

    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.

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

    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

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

    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...

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

    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...

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

    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.

  3. Piezoelectric Shaker Development for High Frequency Calibration of Accelerometers

    Calibration of vibration transducers requires sinusoidal motion over a wide frequency range with low distortion and low cross-axial motion. Piezoelectric shakers are well suited to generate such motion and are suitable for use with laser interferometric methods at frequencies of 3 kHz and above. An advantage of piezoelectric shakers is the higher achievable accelerations and displacement amplitudes as compared to electro-dynamic (ED) shakers. Typical commercial ED calibration shakers produce maximum accelerations from 100 m/s2 to 500 m/s2. Very large ED shakers may produce somewhat higher accelerations but require large amplifiers and expensive cooling systems to dissipate heat. Due to the limitations in maximum accelerations by ED shakers at frequencies above 5 kHz, the amplitudes of the generated sinusoidal displacement are frequently below the resolution of laser interferometers used in primary calibration methods. This limits the usefulness of ED shakers in interferometric based calibrations at higher frequencies.Small piezoelectric shakers provide much higher acceleration and displacement amplitudes for frequencies above 5 kHz, making these shakers very useful for accelerometer calibrations employing laser interferometric measurements, as will be shown in this paper. These piezoelectric shakers have been developed and used at NIST for many years for high frequency calibration of accelerometers. This paper documents the construction and performance of a new version of these shakers developed at NIST for the calibration of accelerometers over the range of 3 kHz to 30 kHz and possibly higher. Examples of typical calibration results are also given.

  4. Polysilicon MEMS accelerometers exposed to shocks: numerical–experimental investigation

    In this work the response of a commercial polysilicon MEMS accelerometer subject to shocks in the range 90–5500 g (g being the gravity acceleration) is studied. In situ measurements are compared with results of numerical simulations, obtained via a two-degrees-of-freedom model of sensor dynamics. It is shown that, despite several sources of nonlinearities, the numerical model can capture the main features of the MEMS transient response. The tested devices did not show malfunctioning, even when subject to acceleration peaks 100 times greater than those characterizing the working regime

  5. Triaxial MEMS accelerometer with screen printed PZT thick film

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

    2010-01-01

    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. 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 and...

  6. Characterisation of a highly symmetrical miniature capacitive triaxial accelerometer

    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...

  7. Vibration Combined High Temperature Cycle Tests for Capacitive MEMS Accelerometers

    Szucs, Z; Hodossy, S; Rencz, M; Poppe, A

    2008-01-01

    In this paper vibration combined high temperature cycle tests for packaged capacitive SOI-MEMS accelerometers are presented. The aim of these tests is to provide useful Design for Reliability information for MEMS designers. A high temperature test chamber and a chopper-stabilized read-out circuitry were designed and realized at BME - DED. Twenty thermal cycles of combined Temperature Cycle Test and Fatigue Vibration Test has been carried out on 5 samples. Statistical evaluation of the test results showed that degradation has started in 3 out of the 5 samples.

  8. Micromachined magnetometer-accelerometer for a navigation system

    Cho, Ji-Man; Kim, Kyung S.; An, Seungdo; Park, HoJoon; Hahm, Ghun

    2002-11-01

    A new type of magnetometer-accelerometer is developed with a silicon micromachining. The operation principle of the sensor is based on the well known Lorentz force caused by the interaction of a current and an external magnetic field on a suspended conducting beam. To realize a new resonant micro sensor detecting both acceleration and the geomagnetic field simultaneously, a conducting line is formed on a spring part of a silicon accelerometer having two mass plates. And a new Samsung MEMS fabrication process is developed for this sensor. The process uses a silicon-on-glass (SOG) wafer, an inverted SOG wafer, and a gold-silicon eutectic bonding for the wafer-level hermetic packaging. To operate the sensor, an ac current of its mechanical resonant frequency is driven through the conducting line. Totally 1 mW is consumed in the current driving element. This newly developed sensor is enough for the 10 degree electronic display of the orientation angle and can be used in a portable navigator such as SmartPhones and PDAs that need a small, low cost and low power electronic compass.

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

    Sekiya, Hidehiko; Kimura, Kentaro; Miki, Chitoshi

    2016-01-01

    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. PMID:26907287

  10. Technique for Determining Bridge Displacement Response Using MEMS Accelerometers

    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.

  11. Physical activity in adolescents – Accelerometer data reduction criteria

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

    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...... resulted in a higher percentage of participants included. In general we found the most substantial differences in compliance when looking at 10–12h (daily wear time), and 5–7days (number of valid days). Only 4.2% of participants had 7 valid days of 12h wear time, whereas 98.8% of participants had at least...... compared to 570 cpm using 90min non-wear. No systematic differences in PA outcomes were found when comparing the range of days and hours. Discussion: We used a systematic approach to illustrate that even small inconsistencies in accelerometer data reduction can have substantial impact on compliance and PA...

  12. Accelerometer data reduction: A comparison of four reduction algorithms on select outcome variables

    PURPOSE: Accelerometers are recognized as a valid and objective tool to assess free-living physical activity. Despite the widespread use of accelerometers, there is no standardized way to process and summarize data from them, which limits our ability to compare results across studies. This paper a) ...

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

    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

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

    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.

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

    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...

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

    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.

  17. Accelerometer recorder and display system for ambulatory patients

    Berka, Martin; Żyliński, Marek; Niewiadomski, Wiktor; Cybulski, Gerard

    2015-09-01

    This paper presents the design of a compact, wearable, rechargeable acceleration recorder to support long-term monitoring of ambulatory patients with motor disorders, and of software to display and analyze its output. The device consists of a microcontroller, operational amplifier, accelerometer, SD card, indicator LED, rechargeable battery, and associated minor components. It can operate for over a day without charging and can continuously collect data for three weeks without downloading to an outside system, as currently configured. With slight modifications, this period could be extended to several months. The accompanying software provides flexible visualization of the acceleration data over long periods, basic file operations and compression for easier archiving, annotation of segments of interest, and functions for calculation of various parameters and detection of immobility and vibration frequencies. Applications in analysis of gait and other movements are discussed.

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

    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.

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

    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)

  20. Physical activity and energy expenditure measurements using accelerometers in older adults.

    Garatachea, N; Torres Luque, G; González Gallego, J

    2010-01-01

    The purpose of this review is to address methodological issues related to accelerometer-based assessments of physical activity (PA) in older individuals. Special interest is also put on recently updated technology. No definitive evidence exists currently to indicate which are the more valid and reliable accelerometer models for use with older people. When it comes to selecting an accelerometer, issues of affordability, product reliability, monitor size, technical support, and comparability with other studies may be equally as important as the relative validity and reliability of an instrument. The accelerometer should be attached as close as possible to the body's center of mass, and in the case of elders using walking aids, it should be placed on the same body side. Variability due to positioning can be reduced with careful training and supervision. Typically, the sampling period is between 3 and 7 days and it is not yet clear if variability exists between weekdays and weekend in the elderly. It is possible that aging effects on physical and cognitive health may limit the ability of an older adult to be compliant with an accelerometer protocol; in this line many methods have been suggested for increasing compliance to protocols for research studies. Accelerometers can provide reliable information on mobility and objective measurement of PA. These activity monitors have significant advantages when compared with other quantitative methods for measurement of energy expenditure. Accelerometers are currently used mainly in a research setting; however, with recent advances, incorporation into clinical and fitness practice is possible and increasing. PMID:20449530

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

    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.

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

    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

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

    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)

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

    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...

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

    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...

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

    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...

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

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

    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.

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

    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...

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

    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).

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

    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

    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

    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. Optimal sensor placement for measuring physical activity with a 3D accelerometer

    Boerema, Simone T.; Lex van Velsen; Leendert Schaake; Thijs M. Tönis; Hermens, Hermie J

    2014-01-01

    Accelerometer-based activity monitors are popular for monitoring physical activity. In this study, we investigated optimal sensor placement for increasing the quality of studies that utilize accelerometer data to assess physical activity. We performed a two-staged study, focused on sensor location and type of mounting. Ten subjects walked at various walking speeds on a treadmill, performed a deskwork protocol, and walked on level ground, while simultaneously wearing five ProMove2 sensors wit...

  15. Clinical assessment of standing and gait in ataxic patients using a triaxial accelerometer

    Matsushima, Akira; Yoshida, Kunihiro; Genno, Hirokazu; Murata, Asuka; Matsuzawa, Setsuko; Nakamura, Katsuya; Nakamura, Akinori; Ikeda, Shu-ichi

    2015-01-01

    Background The aim of this study was to investigate the usefulness of a triaxial accelerometer for the clinical assessment of standing and gait impairment in ataxic patients quantitatively. Fifty-one patients with spinocerebellar ataxia (SCA) or multiple system atrophy with predominant cerebellar ataxia (MSA-C) and 56 healthy control subjects were enrolled. The subjects, with a triaxial accelerometer on their back, were indicated to stand for 30 s in four different conditions (eyes opened or ...

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

    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...

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

    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...

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

    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...

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

    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.

  20. Detection of cavitation behavior using accelerometer and microphone outside of piping at orifice

    Cavitation induced vibration and the consequent erosion of pipes are one aspect of the potential damaging factors in the piping system. In order to prevent such trouble, it is needed to develop a detection method of cavitation. Especially, in a plant system such as nuclear power plants, it is preferable to detect them by measuring outside of pipes during plant operation. In this paper, the detection methods of cavitation using an accelerometer and a microphone were experimentally examined and compared each other. As a result: (1) Output of the accelerometer varied with the cavitation number, and it output voltage increased with development of cavitation. When cavitation occurred, a pulse shaped signal, which might be a shockwave by collapse of cavitation bubbles, was clearly detected. (2) Output distribution of the accelerometer in the flow direction became large where cavitation bubbles collapsed, and output voltage of the accelerometer downstream of the orifice was larger than that of the accelerometer upstream of the orifice. (3) The measurement results with the microphone were similar to those of the accelerometer qualitatively, pulse-shape signals were detected, and difference of output voltages between microphones upstream and downstream of the orifice were measured. In the simultaneous measurements by the accelerometer and the microphone, both sensors detected the shockwave considered to be generated at the same time with a time delay of the microphone. The sound velocity evaluated from the time delay agreed well with the sound velocity in the air. Using the characteristics of the measurement results, cavitation using a microphone without contacting pipes could be performed like an accelerometer mounted on the pipe surface, and cavitation could be detected from the distribution of output voltages in the flow direction even in pipings of a plant without data base to compare. (author)

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

    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 %.

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

    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

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

    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

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

    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.

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

    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.

  6. Detection of rail corrugation based on fiber laser accelerometers

    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. (paper)

  7. Detection of rail corrugation based on fiber laser accelerometers

    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.

  8. Movement prediction using accelerometers in a human population.

    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

  9. Motion analysis of sun salutation using magnetometer and accelerometer

    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.

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

    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. PMID:27225550

  11. BepiColombo ISA accelerometer: ready for launch

    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.

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

    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

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

    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

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

    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.

  15. A Low-Noise DC Seismic Accelerometer Based on a Combination of MET/MEMS Sensors

    Alexander Neeshpapa

    2014-12-01

    Full Text Available Molecular-electronic transducers (MET have a high conversion coefficient and low power consumption, and do not require precision mechanical components thus allowing the construction of cost- and power-efficient seismic accelerometers. Whereas the instrumental resolution of a MET accelerometer within the 0.1–100 Hz frequency range surpasses that of the best Micro-Electro Mechanical Systems (MEMS and even some force-balanced accelerometers, the fundamental inability to register gravity or, in other words, zero frequency acceleration, significantly constrains the further spread of MET-based accelerometers. Ways of obviating this inherent zero frequency insensitivity within MET technology have so far, not been found. This article explores a possible approach to the construction of a hybrid seismic accelerometer combining the superb performance of a MET sensor in the middle and high frequency range with a conventional on chip MEMS accelerometer covering the lower frequencies and gravity. Though the frequency separation of a signal is widely used in various applications, the opposite task, i.e., the combining of two signals with different bandwidths is less common. Based on theoretical research and the analysis of actual sensors’ performance, the authors determined optimal parameters for building a hybrid sensor. Description and results for implementation of the hybrid sensor are given in the Experimental section of the article. Completing a MET sensor with a cost-effective MEMS permitted the construction of a low noise DC accelerometer preserving the noise performance of a MET sensing element. The work presented herein may prove useful in designing other combined sensors based on different technologies.

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

    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...

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

    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.

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

    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.

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

    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)

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

    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.

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

    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.

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

    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)

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

    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.

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

    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.

  5. Ground Based Investigation of Electrostatic Accelerometer in HUST

    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

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

    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.

  7. Theoretical natural frequency of the CTN-10-3/92 accelerometer

    The compression CTN-10-3/92 accelerometer model from ISCTN was design in 1992 and constructed in 1994. Its electrochemical characteristics was defined experimentally and reported in 1995-96 publications. The accelerometer answer has been compare with industrial models of the B and K Danish firm, with successful results, and has been used in measuring practices,also with successful results on validation, by the GDVM working group of the ISCTN The natural frequency of the CTN-10-3/92 accelerometer model calculations are essentially executed for uses requirements satisfaction, consistent in specifying the working tool to rectify and improve the design. The work involve a discussion of the transducer general elastic system and the design. The work involve a discussion of transducer general elastic system and the determination of it resonance frequency

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

    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.

  9. Measuring the needle lift and return timing of a CRDI injector using an accelerometer

    Choong Hoon Lee

    2014-10-01

    Full Text Available The needle lift and return timing of a CRDI (common rail direct injection injector were investigated using an accelerometer and the Bosch injection rate measurement method. The Bosch method was used to measure the fuel injection rate shape when fuel was injected with several patterns. An accelerometer was mounted on the outside of the injector to catch the needle lift and return timing of the injector according to the switching signal of the injector driving voltage. The accelerometer accurately caught the timing of the injector needle lift and return for a single-injection pattern, but it could not for the second or third injection when multiple injections occurred. Only the first needle lift timing of the injector was caught with the injection rate shape obtained from the Bosch method, however, this method cannot identify any other lift or return timing values after the first lift timing.

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

    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.

  11. Suitability of Using the Accelerometer for Impulse Measurement of a Pulse Combustion Tube

    Wahid, Mazlan A.; Ujir, Mohd Haffis; Afifi, Hishamuddin; Mohd Sies, Mohsin

    2010-06-01

    An experimental study of impulse produced by a pulse combustion tube was done to compare between the methods of pendulum and accelerometer for impulse measurement. Stoichiometric mixtures of methane and propane were studied with varying dilution percentages of Nitrogen. Without obstacles, all mixtures exhibit deflagration. To induce detonation, obstacles were used. Detonation occurred for dilution percentage of 42% and lower. From the results, pendulum method always gives higher impulse measurement in deflagration regime while the accelerometer method gives higher results for detonation. The accelerometer method is not suitable for deflagration due to inaccuracies in determining pressure peaks from the measurement. However, it is suitable for studying individual pulses in detonation due to the presence of distinct pressure peaks.

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

    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.

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

    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

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

    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...

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

    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...

  16. RAPID COMMUNICATION: Effect of noise on accelerometer vector measurement in an ideal tri-axial system

    De Freitas, J. M.

    2010-04-01

    A new probability density function which is the direct extension of the Maxwell distribution has been given. The distribution describes the effect of signal plus noise in a tri-axial system of accelerometers. It is shown that an excitation along one axis of a perfectly aligned orthogonal system of accelerometers leads to an apparent angular misalignment in the measured signal when there is random noise in the other two axes. The amplitude distribution with no signal in two axes is the direct analogue of the Rice distribution. The mean and variance of the new distribution are provided.

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

    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

  18. Development of multiple performance indices and system parameter study for the design of a MEMS accelerometer

    For the design of a MEMS accelerometer, proper performance indices should be defined and employed. Performance indices are obtained using either an experimental method or a numerical method. In the present study, a vibration analysis model of a MEMS accelerometer is introduced to calculate three performance indices: sensitivity, measurable acceleration range, and measurable frequency range. The accuracy of the vibration analysis model is first validated by comparing its modal and transient results with those of a commercial finite element code. Measurable acceleration and frequency ranges versus allowable errors for electrical and mechanical sensitivities are obtained and the effects of system parameter variations on the three performance indices are investigated

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

    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...

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

    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

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

    Van Domelen, Dane R; Caserotti, Paolo; Brychta, Robert J; Harris, Tamara B; Patel, Kushang V; Chen, Kong Y; Arnardóttir, Nanna Ýr; Eirikdottir, Gudny; Launer, Lenore J; Gudnason, Vilmundur; Sveinsson, Thórarinn; Jóhannsson, Erlingur; Koster, Annemarie

    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...

  2. A method to deal with installation errors of wearable accelerometers for human activity recognition

    Human activity recognition (HAR) by using wearable accelerometers has gained significant interest in recent years in a range of healthcare areas, including inferring metabolic energy expenditure, predicting falls, measuring gait parameters and monitoring daily activities. The implementation of HAR relies heavily on the correctness of sensor fixation. The installation errors of wearable accelerometers may dramatically decrease the accuracy of HAR. In this paper, a method is proposed to improve the robustness of HAR to the installation errors of accelerometers. The method first calculates a transformation matrix by using Gram–Schmidt orthonormalization in order to eliminate the sensor's orientation error and then employs a low-pass filter with a cut-off frequency of 10 Hz to eliminate the main effect of the sensor's misplacement. The experimental results showed that the proposed method obtained a satisfactory performance for HAR. The average accuracy rate from ten subjects was 95.1% when there were no installation errors, and was 91.9% when installation errors were involved in wearable accelerometers

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

    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.

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

    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

  5. Molecular dynamics simulation study on capacitive nano-accelerometers based on telescoping carbon nanotubes

    We investigated the characteristics of a capacitive nano-accelerometer based on a telescoping carbon nanotube by means of classical molecular dynamics simulations. The position of the telescoping nanotube was controlled by an externally applied force, and feedback sensing was based on the capacitance change. The capacitance variations, which were almost linearly proportional to the applied acceleration, were monitored within an error tolerance

  6. Development of a tri-axial optical accelerometer using two DVD pick-up heads

    Chu, Chih-Liang; Liao, Hong-Wei

    2008-12-01

    This study develops a low-cost, highly-sensitive, three-dimensional optical accelerometer in which the seismic mass comprises four rectangular blocks attached to the ends of a cross-form aluminum structure suspended on four thin steel strips. It is shown through ANSYS finite element (FE) simulations that the thin-strip suspension system restricts the seismic mass to just three degrees of motional freedom, namely one translational motion in the vertical direction and two rotational motions. These displacements are detected using two novel optical sensors based on commercial DVD optical pick-up heads. When the accelerometer experiences a vibrational force, the relative motion between the seismic mass and the base results in a change in the distribution of the reflected light spots on the surfaces of the four-quadrant photodetectors within the two pick-up heads. The resulting changes in the output voltage signals of the two pick-up heads are then used to calculate the corresponding acceleration of the base. The experimental results indicate that the resonance frequencies of the accelerometer in the X, Y and Z-axis directions are 130.51 Hz, 130.63 Hz and 130.90 Hz, respectively. Meanwhile, the sensitivities of the accelerometer in the X, Y and Z-axis directions are 21.28 V/g, 22.94 V/g and 22.75 V/g, respectively.

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

    Stefani, Alessio; Yuan, W.; Markos, C.; Rasmussen, Henrik K.; Andresen, S.; Guastavino, R.; Nielsen, F. K.; Rose, B.; Jespersen, O.; Herholdt-Rasmussen, N.; Bang, Ole

    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...

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

    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.

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

    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

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

    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.

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

    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)

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

    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.

  13. IEEE802.15.6 -based multi-accelerometer WBAN system for monitoring Parkinson's disease.

    Keränen, Niina; Särestöniemi, Mariella; Partala, Juha; Hämäläinen, Matti; Reponen, Jarmo; Seppänen, Tapio; Iinatti, Jari; Jämsä, Timo

    2013-01-01

    In this paper we present a detailed example of a wireless body area network (WBAN) scenario utilizing the recent IEEE802.15.6 standard as applied to a multi-accelerometer system for monitoring Parkinson's disease and fall detection. Ultra wideband physical layer and standard security protocols are applied to meet application requirements for data rate and security. PMID:24110022

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

    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

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

    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.

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

    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.

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

    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.

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

    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...

  19. Validation of two accelerometers to determine mechanical loading of physical activities in children.

    Meyer, Ursina; Ernst, Dominique; Schott, Silvia; Riera, Claudia; Hattendorf, Jan; Romkes, Jacqueline; Granacher, Urs; Göpfert, Beat; Kriemler, Susi

    2015-01-01

    The purpose of this study was to assess the validity of accelerometers using force plates (i.e., ground reaction force (GRF)) during the performance of different tasks of daily physical activity in children. Thirteen children (10.1 (range 5.4-15.7) years, 3 girls) wore two accelerometers (ActiGraph GT3X+ (ACT), GENEA (GEN)) at the hip that provide raw acceleration signals at 100 Hz. Participants completed different tasks (walking, jogging, running, landings from boxes of different height, rope skipping, dancing) on a force plate. GRF was collected for one step per trial (10 trials) for ambulatory movements and for all landings (10 trials), rope skips and dance procedures. Accelerometer outputs as peak loading (g) per activity were averaged. ANOVA, correlation analyses and Bland-Altman plots were computed to determine validity of accelerometers using GRF. There was a main effect of task with increasing acceleration values in tasks with increasing locomotion speed and landing height (P children, although they systematically overestimate GRF. PMID:25620031

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

    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.

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

    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.

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

    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.

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

    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.

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

    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.

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

    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

  6. Quasi-Real Time Estimation of Angular Kinematics Using Single-Axis Accelerometers

    Angelo Cappello

    2013-01-01

    Full Text Available In human movement modeling, the problem of multi-link kinematics estimation by means of inertial measurement units has been investigated by several authors through efficient sensor fusion algorithms. In this perspective a single inertial measurement unit per link is required. This set-up is not cost-effective compared with a solution in which a single-axis accelerometer per link is used. In this paper, a novel fast technique is presented for the estimation of the sway angle in a multi-link chain by using a single-axis accelerometer per segment and by setting the boundary conditions through an ad hoc algorithm. The technique, based on the windowing of the accelerometer output, was firstly tested on a mechanical arm equipped with a single-axis accelerometer and a reference encoder. The technique is then tested on a subject performing a squat task for the knee flexion-extension angle evaluation by using two single-axis accelerometers placed on the thigh and shank segments, respectively. A stereo-photogrammetric system was used for validation. RMSEs (mean ± std are 0.40 ± 0.02° (mean peak-to-peak range of 147.2 ± 4.9° for the mechanical inverted pendulum and 1.01 ± 0.11° (mean peak-to-peak range of 59.29 ± 2.02° for the knee flexion-extension angle. Results obtained in terms of RMSE were successfully compared with an Extended Kalman Filter applied to an inertial measurement unit. These results suggest the usability of the proposed algorithm in several fields, from automatic control to biomechanics, and open new opportunities to increase the accuracy of the existing tools for orientation evaluation.

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

    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.

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

    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)

  9. Development of an optical accelerometer for low-frequency vibration using the voice coil on a DVD pickup head

    In this paper, an economical and highly sensitive optical accelerometer using a commercial optical pickup head is proposed. In the proposed design, the moving part of a voice coil motor (VCM) built in the DVD pickup head is used as the seismic mass which combines with the optical system of the DVD pickup to form an accelerometer. This system not only reduces the design complexity and the manufacturing process but also obtains good measurement effect. Experimental results have shown that the accelerometer at low frequency has a sensitivity of 24.362 V/g

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

    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.

  11. GAC: Energy-Efficient Hybrid GPS-Accelerometer-Compass GSM Localization

    Youssef, Moustafa; El-Derini, Mohamed

    2010-01-01

    Adding location to the available information enables a new category of applications. With the constrained battery on cell phones, energy-efficient localization becomes an important challenge. In this paper we introduce a low-energy calibration-free localization scheme based on the available internal sensors in many of today's phones. We start by energy profiling the different sensors that can be used for localization. Based on that, we propose GAC: a hybrid GPS/accelerometer/compass scheme that depends mainly on using the low-energy accelerometer and compass sensors and uses the GPS infrequently for synchronization. We implemented our system on Android-enabled cell phones and evaluated it in both highways and intra-city driving environments. Our results show that the proposed hybrid scheme has an exponential saving in energy, with a linear loss in accuracy compared to the GPS accuracy. We also evaluate the effect of the different parameters on the energy-accuracy tradeoff.

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

    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.

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

    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

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

    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.

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

    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.

  16. 116 dB dynamic range CMOS readout circuit for MEMS capacitive accelerometer

    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)

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

    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.

  18. Accelerometer-assessed daily physical activity in relation to pain cognition in juvenile idiopathic arthritis

    Nørgaard, Mette; Lomholt, J J; Thastum, M;

    2016-01-01

    , emphasizing the need to explore pain more deeply. The aim of this study was to examine accelerometer-assessed PA in relation to pain cognition in children with JIA. METHOD: Data gathered included disease activity, functional ability, and pain cognition. PA was monitored with a GT1M Actigraph accelerometer...... functional ability, pain intensity, coping strategies, or other pain beliefs. When isolated, disease activity (measured by the 27-joint count Juvenile Arthritis Disease Activity Score, JADAS-27) contributed significantly to the variance in accelerometry, while 'Control' could not significantly explain a...... unique part of the variance. CONCLUSIONS: Objectively measured PA was negatively correlated to disease activity but not to pain intensity. The only pain cognition measurement to reach higher levels of PA was to be in control of pain....

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

    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.

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

    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

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

    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.

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

    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 × 10−8 m/s2/Hz1/2 at 0.1 Hz, while the high-voltage coupling noise is one-order of magnitude lower

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

    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.

  4. Towards Uniform Accelerometry Analysis: A Standardization Methodology to Minimize Measurement Bias Due to Systematic Accelerometer Wear-Time Variation

    Tarun R. Katapally; Muhajarine, Nazeem

    2014-01-01

    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 minim...

  5. Improvements in the Measurement of Physical Activity in Childhood Obesity Research; Lessons from Large Studies of Accelerometers

    Andy Ness; Kate Tilling; Calum Mattocks; Chris Riddoch

    2008-01-01

    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...

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

    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.

  7. Number of Days Required to Estimate Habitual Activity Using Wrist-Worn GENEActiv Accelerometer: A Cross-Sectional Study

    Dillon, Christina B.; Fitzgerald, Anthony P.; Kearney, Patricia M.; Perry, Ivan J; Rennie, Kirsten L.; Kozarski, Robert; Phillips, Catherine M.

    2016-01-01

    Introduction Objective methods like accelerometers are feasible for large studies and may quantify variability in day-to-day physical activity better than self-report. The variability between days suggests that day of the week cannot be ignored in the design and analysis of physical activity studies. The purpose of this paper is to investigate the optimal number of days needed to obtain reliable estimates of weekly habitual physical activity using the wrist-worn GENEActiv accelerometer. Metho...

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

    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...

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

    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...

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

    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...

  11. SVM-based posture identification with a single waist-located triaxial accelerometer

    Rodríguez Martín, Daniel Manuel; Samà Monsonís, Albert; Pérez López, Carlos; Català Mallofré, Andreu; Cabestany Moncusí, Joan; Rodríguez Molinero, Alejandro

    2013-01-01

    Analysis of human body movement is an important research area, specially for health applications. In order to assess the quality of life of people with mobility problems like Parkinson’s disease o stroke patients, it is crucial to monitor and assess their daily life activities. The main goal of this work is the characterization of basic activities using a single triaxial accelerometer located at the waist. This paper presents a novel postural detection algorithm based in SVM methods which is ...

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

    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...

  13. On-line Context Aware Physical Activity Recognition from the Accelerometer and Audio Sensors of Smartphones

    Blachon, David; Cokun, Doruk; Portet, François

    2014-01-01

    Activity Recognition (AR) from smartphone sensors has be-come a hot topic in the mobile computing domain since it can provide ser-vices directly to the user (health monitoring, fitness, context-awareness) as well as for third party applications and social network (performance sharing, profiling). Most of the research effort has been focused on direct recognition from accelerometer sensors and few studies have integrated the audio channel in their model despite the fact that it is a sensor tha...

  14. Swarm accelerometer data processing from raw accelerations to thermospheric neutral densities

    Siemes, Christian; da Encarnacao, Joao de Teixeira; Doornbos, Eelco;

    2016-01-01

    The Swarm satellites were launched on November 22, 2013, and carry accelerometers and GPS receivers as part of their scientific payload. The GPS receivers do not only provide the position and time for the magnetic field measurements, but are also used for determining non-gravitational forces like...... acceleration measurements of Swarm B. We show the results of each processing stage, highlight the difficulties encountered, and comment on the quality of the thermospheric neutral density data set....

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

    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.

  16. Compact dual-frequency fiber laser accelerometer with sub-μg resolution

    Cao, Qian; Jin, Long; Liang, Yizhi; Cheng, Linghao; Guan, Bai-Ou

    2016-06-01

    We demonstrate a compact and high-resolution dual-polarization fiber laser accelerometer. A spring-mass like scheme is constructed by fixing a 10-gram proof mass on the laser cavity to transduce applied vibration into beat-frequency change. The loading is located at the intensity maximum of intracavity light to maximize the optical response. The detection limit reaches 107 ng/Hz1/2 at 200 Hz. The working bandwidth ranges from 60 Hz to 600 Hz.

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

    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 ...

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

    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 ...

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

    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...

  20. Comparison of Accelerometer Cut Points to Estimate Physical Activity in U.S. Adults

    Watson, Kathleen B; Carlson, Susan; Carroll, Dianna D; Fulton, Janet

    2013-01-01

    The purpose of this study was to (1) describe physical activity prevalence, categorized according to the 2008 Physical Activity Guidelines for Americans (2008 Guidelines), using different accelerometer cut points and (2) examine physical activity prevalence patterns by reported cut points across selected characteristics. Cut points from 9 studies were used to estimate physical activity prevalence in a national adult sample (n=6547). Estimates were stratified by validation study activity proto...

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

    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.

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

    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...

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

    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.

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

    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

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

    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...

  6. Fabrication of micro accelerometer and magnetoresistive sensor directly on a ceramic substrate

    Micro-electro-mechanical systems (MEMS) sensors have movable parts: thus, it is difficult to handle them at fabrication because of the possibility of fracture. If a MEMS sensor could be fabricated not only on a silicon substrate but also on a ceramic substrate, which can be used for a package of the end product, the above-mentioned problem about handling would be solved, and its fabrication cost would be reduced. In this presentation, as demonstrations of the sensors directly fabricated on a ceramic package, an accelerometer and a magnetoresistive (MR) sensor are focused on. A micro accelerometer is proposed, which consists of a proof mass and ferroelectric substrate under it. A screen-printed barium titanate (BTO) film on an alumina substrate was employed as ferroelectrics. The sensitivity of the fabricated accelerometer was 0.1 pF g−1. A triaxis MR sensor is proposed, which detects not only x- and y-axes' magnetic field intensities but also that of the z-axis. Namely, not only azimuth but also angle of elevation of the sensor can be detected from triaxis components of the geomagnetic field. A permalloy (FeNi) plate is stood aside from the MR element. The plate distorts magnetic field and generates the x- (or y-) component from the originally z-directional field. A triaxis geomagnetic field was successfully detected by the fabricated sensor

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

    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.

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

    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.

  9. Data generator for a satellite-borne three-axis accelerometer

    Branch, C. G.

    1980-03-01

    Atmospheric drag has a significant effect on low altitude trajectories. To measure this force, an accelerometer will be tested which senses this nonconservative acceleration. The information obtained will then be used to improve the orbit and obtain a more accurate gravity field model. When the raw data is first received, all known systematic effects will be removed. These include gravity gradient and pitch-rate induced accelerations. However, the preprocessed data will still contain anomalies of which there is little or no a priori knowledge. Satellite attitude thruster-induced vibrations are a major source of unmodeled noise. As for the instrument itself, each axis of the accelerometer adds an undetermined bias to the output accelerations. In addition, the conversion of the digital output to engineering units introduces a scale factor error. Other effects may take the form of additive correlated noise and white noise. The first instrument to be flown is the miniature electrostatic accelerometer (MESA). The MESA senses accelerations along the vehicle pitch, roll, and yaw axes. Relying on the accuracy of the vehicle's attitude control system, these axes are assumed to be along the R,R X V, and -R vectors, respectively. Hence, any attitude errors will be reflected in the measurements. The MESA also introduces undetermined scale factor errors and biases. Consequently, a computer program was designed which applies a filter to the processed accelerations. This filter should statistically remove most of the unmodeled corruptions. The filtered data is then input to a special version of the Celest orbit determination program.

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

    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