Modelling of a nanosecond surface discharge actuator
Unfer, T; Boeuf, J P [Universite de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, F-31062 Toulouse cedex 9 (France); CNRS, LAPLACE, F-31062 Toulouse (France)
2009-10-07
Surface dielectric barrier discharges (SDBDs) can modify the boundary layer of a flow and are studied as a possible means to control the flow over an airfoil. In SDBDs driven by sinusoidal voltages in the 1-10 kHz range, momentum is transferred from ions to the neutral gas, as in a corona discharge (ion wind), and the resulting electrohydrodynamic force can generate a flow of several m s{sup -1} in the boundary layer along the surface. In this paper we are interested in a different regime of SDBDs where nanosecond voltage pulses are applied between the electrodes. Recent experiments by the group of Starikovskii have demonstrated that such discharges are able to modify a flow although no significant ion wind can be detected. A two-dimensional self-consistent numerical model of the discharge and gas dynamics in conditions similar to those of these experiments has been developed. The model couples fluid discharge equations with compressible Navier-Stokes equations including momentum and thermal transfer from the plasma to the neutral gas. This is a difficult multi-scale problem and special care has been taken to accurately solve the equations over a large simulation domain and at a relatively low computational cost. The results show that under the conditions of the simulated experiments, fast gas heating takes place in the boundary layer, leading to the generation of a 'micro' shock wave, in agreement with the experiments.
Electrostatic actuators fabricated by surface micromachining techniques
Legtenberg, Rob
1996-01-01
This thesis deals with "electrostatic actuators fabricated by surface micromachining techniques". It presents fabrication techniques, design issues, modelling and performance characteristics of a number of electrostatic actuators. These actuators can be used in future micromechanical devices and systems which have applications such as micropositioning, microfluidics, microsurgery etc.
The Actuator Surface Model: A New Navier-Stokes Based Model for Rotor Computations
Shen, Wen Zhong; Zhang, J.H.; Sørensen, Jens Nørkær
2009-01-01
the chord of the airfoils. The distribution of body force is determined from a set of predefined functions that depend on angle of attack and airfoil shape. The predefined functions are curve fitted using pressure distributions obtained either from viscous-inviscid interactive codes or from full...... Navier-Stokes simulations. The actuator surface technique is evaluated by computing the two-dimensional flow past a NACA 0015 airfoil at a Reynolds number of 10(6) and an angle of attack of 10 deg and by comparing the computed streamlines with the results from a traditional Reynolds-averaged Navier......-Stokes computation. In the last part, the actuator surface technique is applied to compute the flow past a two-bladed vertical axis wind turbine equipped with NACA 0012 airfoils. Comparisons with experimental data show an encouraging performance of the method....
Plasma Diagnostics and Modelling of Nanosecond Pulsed Surface Dielectric Barrier Discharge Actuators
Goekce, Sami
2014-01-01
During the past years, an increasing number of studies have been conducted on the use of electrical discharges for the stabilization of airflows (plasma flow control). Electrical gas discharges transfer energy and momentum to the gas through collisions of free electrons with atoms and molecules. Chemically active species such as ions, radicals and excited species are produced due to these collisions. The use of plasma actuators, notably surface dielectric barrier discharges (SDBD), for flow c...
Optimal smoothing length scale for actuator line models of lifting surfaces
Martinez-Tossas, Luis A
2015-01-01
The actuator line model (ALM) is a commonly used method to represent lifting surfaces such as wind turbine blades within Large-Eddy Simulations (LES). In ALM the lift and drag forces are replaced by an imposed body force which is typically smoothed over several grid points using a Gaussian kernel with some prescribed smoothing width $\\epsilon$. To date, the choice of $\\epsilon$ has most often been based on numerical considerations mostly related to the grid spacing used in LES. However, especially for finely resolved LES with grid spacings on the order or smaller than the chord-length of the blade, the best choice of $\\epsilon$ is not known. Focusing first on the lift force, here we find $\\epsilon$ and the force center location that minimize the square difference between the velocity fields obtained from solving 2D potential flow over Joukowski airfoils and solving the Euler equations including the imposed body force. The latter solution is found for the linearized problem, and is valid for small angles of at...
Modeling and control of precision actuators
Kiong, Tan Kok
2013-01-01
IntroductionGrowing Interest in Precise ActuatorsTypes of Precise ActuatorsApplications of Precise ActuatorsNonlinear Dynamics and ModelingHysteresisCreepFrictionForce RipplesIdentification and Compensation of Preisach Hysteresis in Piezoelectric ActuatorsSVD-Based Identification and Compensation of Preisach HysteresisHigh-Bandwidth Identification and Compensation of Hysteretic Dynamics in Piezoelectric ActuatorsConcluding RemarksIdentification and Compensation of Frict
Improving actuator disk wake model
The wind energy industry has traditionally relied on simple wake models for estimating Wind Turbine (WT) wake losses. Despite limitations, low requirements in terms of detailed rotor information makes their use feasible, unlike more complex models, such as Blade Element Method (BEM) or Actuator Line. Froude's Actuator Disk (AD) does not suffer the simpler model's limitation of prescribing the wake through a closed set of equations, while sharing with them the low rotor data requirements. On the other hand they require some form of parametrization to close the model and calculate total thrust acting on the flow. An Actuator Disk model was developed, using an iterative algorithm based on Froude's one-dimensional momentum theory to determine the WT's performance, proving to be successful in estimating the performance of both machines in undisturbed flow and in the wake of an upstream machines. Before Froude's AD limitations compared to more complex rotor models, load distributions emulating those of a BEM model were tested. The results show that little impact is obtained at 3 rotor diameters downstream and beyond, agreeing with common definition of a far-wake that starts at 1-2 diameters downstream, where rotor characteristics become negligible and atmospheric flow effects dominate
Surface micromachined electrostatically actuated micro peristaltic pump
Xie, Jun; Shih, Jason; Lin, Qiao; Yang, Bozhi; Tai, Yu-Chong
2004-01-01
An electrostatically actuated micro peristaltic pump is reported. The micro pump is entirely surface micromachined using a multilayer parylene technology. Taking advantage of the multilayer technology, the micro pump design enables the pumped fluid to be isolated from the electric field. Electrostatic actuation of the parylene membrane using both DC and AC voltages was demonstrated and applied to fluid pumping based on a 3-phase peristaltic sequence. A maximum flow rate of 1.7 nL min^–1 and a...
Piezoelectric Actuator Modeling Using MSC/NASTRAN and MATLAB
Reaves, Mercedes C.; Horta, Lucas G.
2003-01-01
This paper presents a procedure for modeling structures containing piezoelectric actuators using MSCMASTRAN and MATLAB. The paper describes the utility and functionality of one set of validated modeling tools. The tools described herein use MSCMASTRAN to model the structure with piezoelectric actuators and a thermally induced strain to model straining of the actuators due to an applied voltage field. MATLAB scripts are used to assemble the dynamic equations and to generate frequency response functions. The application of these tools is discussed using a cantilever aluminum beam with a surface mounted piezoelectric actuator as a sample problem. Software in the form of MSCINASTRAN DMAP input commands, MATLAB scripts, and a step-by-step procedure to solve the example problem are provided. Analysis results are generated in terms of frequency response functions from deflection and strain data as a function of input voltage to the actuator.
Cfd modeling of a synthetic jet actuator
Synthetic jet actuators show good promise as an enabling technology for innovative boundary layer flow control applied to external surfaces, like airplane wings, and to internal flows, like those occurring in a curved engine inlet. The appealing characteristics of a synthetic jet are zero-net-mass flux operation and an efficient control effect that takes advantages of unsteady fluid phenomena. The formation of a synthetic jet in a quiescent external air flow is only beginning to be understood and a rational understanding of these devices is necessary before they can be applied to the control of flows outside of the laboratory. The synthetic jet flow generated by a planar orifice is investigated here using computational approach. Computations of the 2D synthetic jet are performed with unsteady RANS modeled with the Realizable κ - ε turbulence model available in FLUENT environment. In this present work, the ability of the first order turbulence model, employed in our computations, to model the formation of the counter-rotating-vortex pair (CVP) that appears in the flow-field was investigated. Computational results were in good agreement with experimental measurements. The effectiveness of such control actuator was tested on separated boundary layer. Preliminary investigation were presented and discussed
Modelling of dielectric barrier discharge plasma actuators with thick electrodes
Hoskinson, A R; Hershkowitz, N, E-mail: hershkowitz@engr.wisc.edu [Department of Engineering Physics, University of Wisconsin-Madison, Madison, WI 53706 (United States)
2011-03-02
We have developed a new two-dimensional fluid simulation to model the plasma dynamics in surface dielectric barrier discharges operating in air. Single-barrier (one electrode insulated) and double-barrier (both electrodes insulated) discharges have been observed to generate a force in the nearby air, making them potentially useful as aerodynamic actuators. Many previous simulations of such discharges have modelled the electrodes as thin strips. We instead consider plasma actuators including cylindrical electrodes of various sizes. In single-barrier actuators, the size of the exposed electrode qualitatively affects the discharge dynamics, particularly with a negative-going applied voltage. For both geometries, the simulations predict the formation of plasma structures similar to those imaged in previous experiments. Experimentally observed increases in forces for actuators with smaller high-voltage electrodes were only reproduced for the single-barrier geometry. Due to limitations of computational power, voltage rates of change for all simulations were higher than those used in experiments.
Nonlinear Model-Based Fault Detection for a Hydraulic Actuator
Van Eykeren, L.; Chu, Q.P.
2011-01-01
This paper presents a model-based fault detection algorithm for a specific fault scenario of the ADDSAFE project. The fault considered is the disconnection of a control surface from its hydraulic actuator. Detecting this type of fault as fast as possible helps to operate an aircraft more cost effect
Active Flow Control Using Sweeping Jet Actuators on a Semi-Span Wing Model
Melton, LaTunia Pack; Koklu, Mehti
2016-01-01
Wind tunnel experiments were performed using active flow control on an unswept semispan wing model with a 30% chord trailing edge flap to aid in the selection of actuators for a planned high Reynolds number experiment. Two sweeping jet actuator sizes were investigated to determine the influence of actuator size on the active flow control system efficiency. Sweeping jet actuators with orifice sizes of 1 mm x 2 mm and 2 mm x 4 mm were selected because of the differences in actuator jet sweep angle. The parameters that were varied include actuator momentum, freestream velocity, and trailing edge flap deflection angle. Steady and unsteady pressure data, Particle Image Velocimetry data, and force and moment data were acquired to assess the performance of the two actuators. In addition to the wind tunnel experiments, benchtop studies of the actuators were performed to characterize the jets produced by each actuator. Benchtop investigations of the smaller actuator reveal that the jet exiting the actuator has a reduced sweep angle compared to published data for larger versions of this type of actuator. The larger actuator produces an oscillating jet that attaches to the external di?user walls at low supply pressures and produces the expected sweep angles. The AFC results using the smaller actuators show that while the actuators can control flow separation, the selected spacing of 3.3 cm may be too large due to the reduced sweep angle. In comparison, the spacing for the larger actuators, 6.6 cm, appears to be optimal for the Mach numbers investigated. Particle Image Velocimetry results are presented and show how the wall jets produced by the actuators cause the flow to attach to the flap surface.
Electrochemical fabrication and modelling of mechanical behavior of a tri-layer polymer actuator
Stability and performance of electrochemically synthesized tri-layer polypyrrole based actuators were reported. Concentrations were optimized as 0.05 M pyrrole and 0.05 M tetrabutylammonium hexaflurophosphate in propylene carbonate (PC). The force output of the actuators ranged from 0.2 to 0.4 mN. Cyclic deflection tests on PC based actuators for a duration of 3 h indicated that the displacement decreased by 60%. However, actuation could be regenerated by immersing the actuator into the electrolyte solution. Surface resistivity measurements on the actuators prior to and after 3 h continuous deflection did not show any significant change in the resistivity of the PPy layer. A triple-layer model of the polymer actuator was developed based on the classic bending beam theory by considering strain continuity between PPy and PVDF. Results predicted by the model were in good agreement with the experimental data.
Farrokhabadi, Amin; Mohebshahedin, Abed; Rach, Randolph; Duan, Jun-Sheng
2016-01-01
The influence of the surface energy on the instability of nano-structures under the electrostatic force has been investigated in recent years by different researchers. It appears that in all prior research, the response of all structures becomes softer due to the surface effects. In the present study, the pull-in instability of a NEMS device incorporating the electrostatic force and Casimir intermolecular attraction for different values of the surface parameter is investigated by the Duan-Rach method of determined coefficients (MDC) in order to identify the remarkable effect of the surface energy. Although the obtained results verify the behavior of such structures in presence of the fringing field and the Casimir attraction same as the previous investigations, however the incremental effects of the surface energy cause the aforementioned structures to behave more stiffly in contrast.
Electromechanical modelling for piezoelectric flextensional actuators
The piezoelectric flextensional actuator investigated in this paper comprises three pre-stressed piezoceramic lead zirconate titanate (PZT) stacks and an external, flexure-hinged, mechanical amplifier configuration. An electromechanical model is used to relate the electrical and mechanical domains, comprising the PZT stacks and the flexure mechanism, with the dynamic characteristics of the latter represented by a multiple degree-of-freedom dynamic model. The Maxwell resistive capacitive model is used to describe the nonlinear relationship between charge and voltage within the PZT stacks. The actuator model parameters and the electromechanical couplings of the PZT stacks, which describe the energy transfer between the electrical and mechanical domains, are experimentally identified without disassembling the embedded piezoceramic stacks. To verify the electromechanical model, displacement and frequency experiments are performed. There was good agreement between modelled and experimental results, with less than 1.5% displacement error. This work outlines a general process by which other pre-stressed piezoelectric flextensional actuators can be characterized, modelled and identified in a non-destructive way. (paper)
Analytical dynamic modeling of fast trilayer polypyrrole bending actuators
Analytical modeling of conjugated polymer actuators with complicated electro-chemo-mechanical dynamics is an interesting area for research, due to the wide range of applications including biomimetic robots and biomedical devices. Although there have been extensive reports on modeling the electrochemical dynamics of polypyrrole (PPy) bending actuators, mechanical dynamics modeling of the actuators remains unexplored. PPy actuators can operate with low voltage while producing large displacement in comparison to robotic joints, they do not have friction or backlash, but they suffer from some disadvantages such as creep and hysteresis. In this paper, a complete analytical dynamic model for fast trilayer polypyrrole bending actuators has been proposed and named the analytical multi-domain dynamic actuator (AMDDA) model. First an electrical admittance model of the actuator will be obtained based on a distributed RC line; subsequently a proper mechanical dynamic model will be derived, based on Hamilton's principle. The purposed modeling approach will be validated based on recently published experimental results
Otten, Alexander; van Vuuren, Wieke; Stienen, Arno; van Asseldonk, Edwin; Schouten, Alfred; van der Kooij, Herman
2011-01-01
Robotics used for diagnostic measurements on, e.g. stroke survivors, require actuators that are both stiff and compliant. Stiffness is required for identification purposes, and compliance to compensate for the robots dynamics, so that the subject can move freely while using the robot. A hydraulic actuator can act as a position (stiff) or a torque (compliant) actuator. The drawback of a hydraulic actuator is that it behaves nonlinear. This article examines two methods for controlling a nonlinear hydraulic actuator. The first method that is often applied uses an elastic element (i.e. spring) connected in series with the hydraulic actuator so that the torque can be measured as the deflection of the spring. This torque measurement is used for proportional integral control. The second method of control uses the inverse of the model of the actuator as a linearizing controller. Both methods are compared using simulation results. The controller designed for the series elastic hydraulic actuator is faster to implement, but only shows good performance for the working range for which the controller is designed due to the systems nonlinear behavior. The elastic element is a limiting factor when designing a position controller due to its low torsional stiffness. The model-based controller linearizes the nonlinear system and shows good performance when used for torque and position control. Implementing the model-based controller does require building and validating of the detailed model. PMID:22275654
The application of SMA spring actuators to a lightweight modular compliant surface bioinspired robot
Stone, David L.; Cranney, John; Liang, Robert; Taya, Minoru
2004-07-01
The DARPA Sponsored Compliant Surface Robotics (CSR) program pursues development of a high mobility, lightweight, modular, morph-able robot for military forces in the field and for other industrial uses. The USTLAB and University of Washington Center for Intelligent Materials and Systems (CIMS) effort builds on USTLAB proof of concept feasibility studies and demonstration of a 4, 6, or 8 wheeled modular vehicle with articulated leg-wheel assemblies. A collaborative effort between USTLAB and UW-CIMS explored the application of Shape Memory Alloy Nickel Titanium Alloy springs to a leg extension actuator capable of actuating with 4.5 Newton force over a 50 mm stroke. At the completion of Phase II, we have completed mechanical and electronics engineering design and achieved conventional actuation which currently enable active articulation, enabling autonomous reconfiguration for a wide variety of terrains, including upside down operations (in case of flip over), have developed a leg extension actuator demonstration model, and we have positioned our team to pursue a small vehicle with leg extension actuators in follow on work. The CSR vehicle's modular spider-like configuration facilitates adaptation to many uses and compliance over rugged terrain. The developmental process, actuator and vehicle characteristics will be discussed.
Multiscale modeling and topology optimization of poroelastic actuators
Andreasen, Casper Schousboe; Sigmund, Ole
2012-01-01
This paper presents a method for design of optimized poroelastic materials which under internal pressurization turn into actuators for application in, for example, linear motors. The actuators are modeled in a two-scale fluid–structure interaction approach. The fluid saturated material microstruc......This paper presents a method for design of optimized poroelastic materials which under internal pressurization turn into actuators for application in, for example, linear motors. The actuators are modeled in a two-scale fluid–structure interaction approach. The fluid saturated material...
Modeling Populations of Thermostatic Loads with Switching Rate Actuation
Totu, Luminita Cristiana; Wisniewski, Rafal; Leth, John-Josef
We model thermostatic devices using a stochastic hybrid description, and introduce an external actuation mechanism that creates random switch events in the discrete dynamics. We then conjecture the form of the Fokker-Planck equation and successfully verify it numerically using Monte Carlo...... simulations. The actuation mechanism and subsequent modeling result are relevant for power system operation....
Measurements and Simulations of Surface Dielectric Barrier Discharges Used as Plasma Actuators
Hoskinson, Alan R.
2012-01-01
This report is a Ph.D. dissertation performed under NRA cooperative agreement and submitted as part of the final report. Asymmetric surface dielectric barrier discharges (DBDs) have shown promise for use as aerodynamic actuators for active flow control. In this project we studied DBD actuators experimentally and numerically. Our DBDs used a symmetric triangular high voltage waveform to generate plasma in atmospheric pressure air. Time-averaged measurements indicated that the induced force of a single barrier actuator design (one electrode insulated from the plasma) can be increased exponentially above the results of previous studies by decreasing both the length and thickness of the electrode exposed to the plasma. This increased force may allow these devices to control flow separation in a wider range of flow environments. Experiments using an intensified digital camera to examine the plasma on time scales of a few nanoseconds showed that, in addition to the previously-observed filamentary and jet-like plasma structures, discharges with very thin exposed electrodes exhibited a weak but constant plasma immediately adjacent to those electrodes. In double-barrier actuators (both electrodes insulated), decreasing the diameter of the narrower electrode lead to increasing forces, and recorded images showed the simultaneous existence of both filamentary and jet-like plasma structures. The development and application of a time-dependent, two-dimensional computational fluid plasma model has aided in understanding the detailed physics of surface DBDs at all-time scales. For simulated single-barrier discharges, the model qualitatively reproduced the filamentary and jet-like micro-discharge structures. The model was somewhat successful in reproducing the observed characteristics of double-barrier actuators. For both actuator geometries, the model indicated that the majority of the forces induced on the neutral gas occur in between micro-discharges as the plasmas decay.
Numerical modeling of shape memory alloy linear actuator
Jani, Jaronie Mohd; Huang, Sunan; Leary, Martin; Subic, Aleksandar
2015-09-01
The demand for shape memory alloy (SMA) actuators in high-technology applications is increasing; however, there exist technical challenges to the commercial application of SMA actuator technologies, especially associated with actuation duration. Excessive activation duration results in actuator damage due to overheating while excessive deactivation duration is not practical for high-frequency applications. Analytical and finite difference equation models were developed in this work to predict the activation and deactivation durations and associated SMA thermomechanical behavior under variable environmental and design conditions. Relevant factors, including latent heat effect, induced stress and material property variability are accommodated. An existing constitutive model was integrated into the proposed models to generate custom SMA stress-strain curves. Strong agreement was achieved between the proposed numerical models and experimental results; confirming their applicability for predicting the behavior of SMA actuators with variable thermomechanical conditions.
Nanoscale actuation of electrokinetic flows on thermoreversible surfaces.
Paumier, Guillaume; Sudor, Jan; Gue, Anne-Marie; Vinet, Françoise; Li, Meng; Chabal, Yves J; Estève, Alain; Djafari-Rouhani, Mehdi
2008-03-01
We report on a novel approach for controlling nanohydrodynamic properties at the solid-liquid interfaces through the use of stimuli-responding polymer coatings. The end-tethered polymers undergo a phase separation upon external activation. The reversible change in the thickness and polarity of the grafted polymers yields in a dynamic control of the surface-generated, electrokinetic phenomena. Nonactivated, swollen polymers are thicker than the electrical double layer (EDL) and prohibit the development of an EOF even on charged surfaces. On the other hand, activated polymer chains shrink and become thinner than the EDL and allow for the EOF to build up unimpeded. We show here that, for given experimental conditions, the EOF velocity on the shrunken surface is 35 times greater than the one on the nonactivated surface. Furthermore, we reveal that coupling of such surfaces with dense arrays of thermal actuators developed in our laboratory can lead to novel micro- and nanofluidic devices. PMID:18348218
Nonlinear actuation dynamics of driven Casimir oscillators with rough surfaces
Broer, Wijnand; Svetovoy, Vitaly B; Knoester, Jasper; Palasantzas, George
2015-01-01
At separations below 100 nm, Casimir-Lifshitz forces strongly influence the actuation dynamics of micro-electromechanical systems (MEMS) in dry vacuum conditions. For a micron size plate oscillating near a surface, which mimics a frequently used setup in experiments with MEMS, we show that the roughness of the surfaces significantly influences the qualitative dynamics of the oscillator. Via a combination of analytical and numerical methods, it is shown that surface roughness leads to a clear increase of initial conditions associated with chaotic motion, that eventually lead to stiction between the surfaces. Since stiction leads to malfunction of MEMS oscillators, our results are of central interest for the design of microdevices. Moreover, they are of significance for fundamentally motivated experiments performed with MEMS.
Nonlinear Actuation Dynamics of Driven Casimir Oscillators with Rough Surfaces
Broer, Wijnand; Waalkens, Holger; Svetovoy, Vitaly B.; Knoester, Jasper; Palasantzas, George
2015-11-01
At separations below 100 nm, Casimir-Lifshitz forces strongly influence the actuation dynamics of microelectromechanical systems (MEMS) in dry vacuum conditions. For a micron-size plate oscillating near a surface, which mimics a frequently used setup in experiments with MEMS, we show that the roughness of the surfaces significantly influences the qualitative dynamics of the oscillator. Via a combination of analytical and numerical methods, it is shown that surface roughness leads to a clear increase of initial conditions associated with chaotic motion, that eventually lead to stiction between the surfaces. Since stiction leads to a malfunction of MEMS oscillators, our results are of central interest for the design of microdevices. Moreover, stiction is of significance for fundamentally motivated experiments performed with MEMS.
Monolithic integration of waveguide structures with surface-micromachined polysilicon actuators
Smith, J.H.; Carson, R.F.; Sullivan, C.T.; McClellan, G.
1996-03-01
The integration of optical components with polysilicon surface micromechanical actuation mechanisms show significant promise for signal switching, fiber alignment, and optical sensing applications. Monolithically integrating the manufacturing process for waveguide structures with the processing of polysilicon actuators allows actuated waveguides to take advantage of the economy of silicon manufacturing. The optical and stress properties of the oxides and nitrides considered for the waveguide design along with design, fabrication, and testing details for the polysilicon actuators are presented.
Analytical model for an electrostatically actuated miniature diaphragm compressor
This paper presents a new analytical approach for quasi-static modeling of an electrostatically actuated diaphragm compressor that could be employed in a miniature scale refrigeration system. The compressor consists of a flexible circular diaphragm clamped at its circumference. A conformal chamber encloses the diaphragm completely. The membrane and the chamber surfaces are coated with metallic electrodes. A potential difference applied between the diaphragm and the chamber pulls the diaphragm toward the chamber surface progressively from the outer circumference toward the center. This zipping actuation reduces the volume available to the refrigerant gas, thereby increasing its pressure. A segmentation technique is proposed for analysis of the compressor by which the domain is divided into multiple segments for each of which the forces acting on the diaphragm are estimated. The pull-down voltage to completely zip each individual segment is thus obtained. The required voltage for obtaining a specific pressure rise in the chamber can thus be determined. Predictions from the model compare well with other simulation results from the literature, as well as to experimental measurements of the diaphragm displacement and chamber pressure rise in a custom-built setup
Model and control of tendon actuated robots
Palli, Gianluca
2007-01-01
The use of tendons for the transmission of the forces and the movements in robotic devices has been investigated from several researchers all over the world. The interest in this kind of actuation modality is based on the possibility of optimizing the position of the actuators with respect to the moving part of the robot, in the reduced weight, high reliability, simplicity in the mechanic design and, finally, in the reduced cost of the resulting kinematic chain. After a brie...
Microparticle manipulation on the surface of a piezoceramic actuator
deSa, J.; Zhang, Q.; Ergezen, E.; Lec, R.
2010-10-01
In this paper, a technique called piezoelectric interfacial particle manipulator (PIPM) for the manipulation of single and multiple microparticles on the surface of a piezoelectric actuator is demonstrated. The PIPM is capable of controlled manipulation of single and multiple microparticles ranging in size from 0.5 to 50 µm. Piezoelectrically excited bulk modes of vibration, ranging from 10 kHz to 2 MHz, are used to generate a complex distribution of manipulation forces acting in opposition to particle-surface normal adhesion and tangential frictional forces. The vibration of the PIPM is characterized using a finite element method (FEM) simulation and a theoretical study of the particle-surface interfacial forces. A comparative study of the manipulation forces and the adhesive particle-surface interfacial forces, measured using atomic force microscopy, is performed. The results confirm the ability of the PIPM to overcome adhesion forces ranging from 10 to 250 nN for particles ranging in radii from 10 to 30 µm. Furthermore, reproducible high throughput particle manipulation is demonstrated via the translation of a 25 µm stainless steel particle, over a distance 600 times its radius, with an average speed of 5 mm s-1. Experimental results correlated with theoretical expectations indicate that the PIPM can prove to be a versatile tool for the controlled non-destructive manipulation of single as well as multiple microparticles in the fields of biosensors, tissue engineering, biochips, micro-fabrication and MEMS devices.
Dynamic modeling of brushless dc motors for aerospace actuation
Demerdash, N. A.; Nehl, T. W.
1980-01-01
A discrete time model for simulation of the dynamics of samarium cobalt-type permanent magnet brushless dc machines is presented. The simulation model includes modeling of the interaction between these machines and their attached power conditioners. These are transistorized conditioner units. This model is part of an overall discrete-time analysis of the dynamic performance of electromechanical actuators, which was conducted as part of prototype development of such actuators studied and built for NASA-Johnson Space Center as a prospective alternative to hydraulic actuators presently used in shuttle orbiter applications. The resulting numerical simulations of the various machine and power conditioner current and voltage waveforms gave excellent correlation to the actual waveforms collected from actual hardware experimental testing. These results, numerical and experimental, are presented here for machine motoring, regeneration and dynamic braking modes. Application of the resulting model to the determination of machine current and torque profiles during closed-loop actuator operation were also analyzed and the results are given here. These results are given in light of an overall view of the actuator system components. The applicability of this method of analysis to design optimization and trouble-shooting in such prototype development is also discussed in light of the results at hand.
Non-Linear Finite Element Modeling of THUNDER Piezoelectric Actuators
Taleghani, Barmac K.; Campbell, Joel F.
1999-01-01
A NASTRAN non-linear finite element model has been developed for predicting the dome heights of THUNDER (THin Layer UNimorph Ferroelectric DrivER) piezoelectric actuators. To analytically validate the finite element model, a comparison was made with a non-linear plate solution using Von Karmen's approximation. A 500 volt input was used to examine the actuator deformation. The NASTRAN finite element model was also compared with experimental results. Four groups of specimens were fabricated and tested. Four different input voltages, which included 120, 160, 200, and 240 Vp-p with a 0 volts offset, were used for this comparison.
Nonlinear finite element modeling of THUNDER piezoelectric actuators
Taleghani, Barmac K.; Campbell, Joel F.
1999-06-01
A NASTRAN non-linear finite element model has been developed for predicting the dome heights of THUNDER (Thin Layer Unimorph Ferroelectric Driver) piezoelectric actuators. To analytically validate the finite element model, a comparison was made with a non-linear plate solution using Von Karmen's approximation. A 500 volt input was used to examine the actuator deformation. The NASTRAN finite element model was also compared with experimental results. Four groups of specimens were fabricated and tested. Four different input voltages, which included 120, 160, 200, and 240 Vp-p with a 0 volts offset, were used for this comparison.
Verification and validation of an actuator disc model
Réthoré, Pierre-Elouan; Laan, van der, Paul Maarten; Troldborg, Niels;
2014-01-01
Wind turbine wake can be studied in computational fluid dynamics with the use of permeable body forces (e.g. actuator disc, line and surface). This paper presents a general flexible method to redistribute wind turbine blade forces as permeable body forces in a computational domain. The method can...
The Venus flytrap uses bistability, the structural characteristic of its leaf, to actuate the leaf's rapid closing motion for catching its prey. This paper presents a flytrap-inspired robot and novel actuation mechanism that exploits the structural characteristics of this structure and a developable surface. We focus on the concept of exploiting structural characteristics for actuation. Using shape memory alloy (SMA), the robot actuates artificial leaves made from asymmetrically laminated carbon fiber reinforced prepregs. We exploit two distinct structural characteristics of the leaves. First, the bistability acts as an implicit actuator enabling rapid morphing motion. Second, the developable surface has a kinematic constraint that constrains the curvature of the artificial leaf. Due to this constraint, the curved artificial leaf can be unbent by bending the straight edge orthogonal to the curve. The bending propagates from one edge to the entire surface and eventually generates an overall shape change. The curvature change of the artificial leaf is 18 m−1 within 100 ms when closing. Experiments show that these actuation mechanisms facilitate the generation of a rapid and large morphing motion of the flytrap robot by one-way actuation of the SMA actuators at a local position. (paper)
DYNAMIC FREE ENERGY HYSTERESIS MODEL IN MAGNETOSTRICTIVE ACTUATORS
无
2006-01-01
A dynamic free energy hysteresis model in magnetostrictive actuators is presented. It is the free energy hysteresis model coupled to an ordinary different equation in an unusual way. According to its special structure, numerical implementation method of the dynamic model is provided. The resistor parameter in the dynamic model changes according to different frequency ranges. This makes numerical implementation results reasonable in the discussed operating frequency range. The validity of the dynamic free energy model is illustrated by comparison with experimental data.
Dynamic response modelling and characterization of a vertical electrothermal actuator
Mathematical modelling and characterization of the dynamic response of a microelectromechanical system (MEMS) electrothermal actuator are presented in this paper. The mathematical model is based on a second-order partial differential equation (one-dimensional heat transfer) and a second-order ordinary differential equation (mechanical dynamic equation). The simulations are implemented using the piecewise finite difference method and the Runge–Kutta algorithm. The electrothermal modelling includes thermal conduction, convective thermal loss and radiation effects. The temperature dependence of resistivity and thermal conductivity of single crystal silicon have also been taken into consideration in the electrothermal modelling. It is calculated from the simulation results that the 'cold' beam of the electrothermal actuator is not only a mechanical constraint but also a thermal response compensation structure. The 0–90% electrothermal rise times for the individual 'hot' and 'cold' beams are calculated to be 32.9 ms and 42.8 ms, respectively, while the 0–90% electrothermal rise time for the whole actuator is calculated to be 17.3 ms. Nonlinear cubic stiffness has been considered in the thermal-mechanical modelling. Dynamic performances of the device have been characterized using a laser vibrometer, and the 0–90% thermal response time of the whole structure has been measured to be 16.8 ms, which matches well with the modelling results. The displacements of the device under different driving conditions and at resonant frequency have been modelled and measured, and the results from both modelling and experiment agree reasonably well. This work provides a comprehensive understanding of the dynamic behaviour of the electrothermal actuation mechanism. The model will be useful for designing control systems for microelectrothermal actuated devices
Han, Jae-Hung; Tani, Junji; Qiu, Jinhao
2006-04-01
This paper presents a numerical and experimental investigation on active flutter suppression of a swept-back cantilevered lifting surface using piezoelectric (PZT) actuation. A finite element method, a panel aerodynamic method, and the minimum state-space realization are involved in the development of the equation of motion in state-space, which is efficiently used for the analysis of the system and design of control laws with a modern control framework. PZT actuators, bonded symmetrically on the plate, are optimally grouped into two equivalent actuator sets using genetic algorithms to enhance controllability. H2- and μ-synthesized control laws are designed and the flutter suppression performance is evaluated via wind tunnel testing. In the μ-synthesis design, a simple parametric uncertainty model is used to take into account the system changes with respect to airflow speed. Both controllers show comparable flutter suppression performance around the flutter point. However, the μ-synthesized controller shows improved behavior over a wide flow speed range.
Modeling and control of a self-sensing polymer metal composite actuator
An ion polymer metal composite (IPMC) is an electro-active polymer (EAP) that bends in response to a small applied electrical field as a result of mobility of cations in the polymer network and vice versa. One drawback in the use of an IPMC is the sensing problem for such a small size actuator. The aim of this paper is to develop a physical model for a self-sensing IPMC actuator and to verify its applicability for practical position control. Firstly, ion dynamics inside a polymer membrane is investigated with an asymmetric solution in the presence of distributed surface resistance. Based on this analysis, a modified equivalent circuit and a simple configuration to realize the self-sensing IPMC actuator are proposed. Mathematical modelling and experimental evaluation indicate that the bending curvature can be obtained accurately using several feedback voltage signals along with the IPMC length. Finally, the controllability of the developed self-sensing IPMC actuator is investigated using a robust position control. Experimental results prove that the self-sensing characteristics can be applied in engineering control problems to provide a more convenient sensing method for IPMC actuating systems. (paper)
Modelling and control of double-cone dielectric elastomer actuator
Branz, F.; Francesconi, A.
2016-09-01
Among various dielectric elastomer devices, cone actuators are of large interest for their multi-degree-of-freedom design. These objects combine the common advantages of dielectric elastomers (i.e. solid-state actuation, self-sensing capability, high conversion efficiency, light weight and low cost) with the possibility to actuate more than one degree of freedom in a single device. The potential applications of this feature in robotics are huge, making cone actuators very attractive. This work focuses on rotational degrees of freedom to complete existing literature and improve the understanding of such aspect. Simple tools are presented for the performance prediction of the device: finite element method simulations and interpolating relations have been used to assess the actuator steady-state behaviour in terms of torque and rotation as a function of geometric parameters. Results are interpolated by fit relations accounting for all the relevant parameters. The obtained data are validated through comparison with experimental results: steady-state torque and rotation are determined at a given high voltage actuation. In addition, the transient response to step input has been measured and, as a result, the voltage-to-torque and the voltage-to-rotation transfer functions are obtained. Experimental data are collected and used to validate the prediction capability of the transfer function in terms of time response to step input and frequency response. The developed static and dynamic models have been employed to implement a feedback compensator that controls the device motion; the simulated behaviour is compared to experimental data, resulting in a maximum prediction error of 7.5%.
Electrical actuation-induced droplet transport on smooth and superhydrophobic surfaces
Bahadur, Vaibhav; Garimella, Suresh
2010-01-01
Electrical control of liquid droplet motion and wettability has wide-ranging applications in the field of MEMS, lab-on-a-chip devices and surface engineering, in view of the resulting enhanced flow control opportunities, low power consumption and the absence of mechanical moving parts. This article summarizes recent progress towards understanding of the fundamentals underlying electrical actuation of droplets on smooth and superhydrophobic surfaces. Electrical actuation of liquid droplets wit...
Nonlinear Hamiltonian modelling of magnetic shape memory alloy based actuators.
Gauthier, Jean-Yves; Hubert, Arnaud; Abadie, Joël; Chaillet, Nicolas; Lexcellent, Christian
2008-01-01
This paper proposes an application of the Lagrangian formalism and its Hamiltonian extension to design, model and control a mechatronic system using Magnetic Shape Memory Alloys. In this aim, an original dynamical modelling of a Magnetic Shape Memory Alloy based actuator is presented. Energy-based techniques are used to obtain a coherent modelling of the magnetical, mechanical and thermodynamic phenomena. The Lagrangian formalism, well suited in such a case, is introduced and used to take int...
Design, test and model of a hybrid magnetostrictive hydraulic actuator
Chaudhuri, Anirban; Yoo, Jin-Hyeong; Wereley, Norman M.
2009-08-01
The basic operation of hybrid hydraulic actuators involves high frequency bi-directional operation of an active material that is converted to uni-directional motion of hydraulic fluid using valves. A hybrid actuator was developed using magnetostrictive material Terfenol-D as the driving element and hydraulic oil as the working fluid. Two different lengths of Terfenol-D rod, 51 and 102 mm, with the same diameter, 12.7 mm, were used. Tests with no load and with load were carried out to measure the performance for uni-directional motion of the output piston at different pumping frequencies. The maximum no-load flow rates were 24.8 cm3 s-1 and 22.7 cm3 s-1 with the 51 mm and 102 mm long rods respectively, and the peaks were noted around 325 Hz pumping frequency. The blocked force of the actuator was close to 89 N in both cases. A key observation was that, at these high pumping frequencies, the inertial effects of the fluid mass dominate over the viscous effects and the problem becomes unsteady in nature. In this study, we also develop a mathematical model of the hydraulic hybrid actuator in the time domain to show the basic operational principle under varying conditions and to capture phenomena affecting system performance. Governing equations for the pumping piston and output shaft were obtained from force equilibrium considerations, while compressibility of the working fluid was taken into account by incorporating the bulk modulus. Fluid inertia was represented by a lumped parameter approach to the transmission line model, giving rise to strongly coupled ordinary differential equations. The model was then used to calculate the no-load velocities of the actuator at different pumping frequencies and simulation results were compared with experimental data for model validation.
Design of a radio telescope surface segment actuator based on a form-closed eccentric cam
Smith, David R.
2014-07-01
As radio telescopes have reached larger diameters and higher frequencies, it is typically not possible to meet their surface accuracy specifications using passive homology-based designs. The most common solution to this problem in the current generation of large, high-frequency radio telescopes is to employ a system of linear actuators to correct the surface shape of the primary reflector. The exact specifications of active surface actuators vary with the telescope. However, they have many common features, some of which drive their design. In general, these actuators must provide precise and repeatable positioning under significant loads during operation and they must withstand even higher loads for survival conditions. For general safety, they typically must hold position in the event of a power failure and must incorporate position limits, whether electrical, mechanical, or both. Because the number of actuators is generally high for large active surfaces (hundreds or even thousands of actuators), they must also be reliable and of reasonable individual cost. Finally, for maximum flexibility in their installation, they must be compact. This paper presents a concept for an active surface actuator based on a form-closed eccentric cam (kinematically, a Scotch Yoke mechanism). Such a design is limited in stroke, but offers potential advantages in terms of manufacture, compactness, measurement, and survival loading. The paper demonstrates that some of the expected advantages cannot be practically realized, due to dimensions that are driven by survival loading conditions. As a result, this concept is likely to offer an advantage over conventional screw-type actuators only for cases where actuator runaway and stall are the driving considerations.
Evaluation of Breaking Performance in Vibration-Assisted Electrostatic Surface Induction Actuator
Nemoto, Takeru; Zsurzsan, Tiberiu-Gabriel; Yamamoto, Akio
2015-01-01
This paper evaluates breaking performance of an electrostatic surface induction actuator. The actuator is equipped with piezoelectric vibrator such that the friction between the slider and the stator electrodes can be dramatically reduced by squeeze-film effect. In such an actuator, the friction...... force can be changed by turning on and off the vibrator. The friction change can be utilized for high-performance slider motion control; for example, friction can be increased by switching off the vibrator when the slider needs to stop. In this paper, we evaluated how fast the slider can stop in several...
Prahlad, Harsha; Pelrine, Ron; Kornbluh, Roy; von Guggenberg, Philip; Chhokar, Surjit; Eckerle, Joseph; Rosenthal, Marcus; Bonwit, Neville
2005-05-01
Many different actuator configurations based on SRI International"s dielectric elastomer (DE) type of electroactive polymer (EAP) have been developed for a variety of applications. These actuators have shown excellent actuation properties including maximum actuation strains of up to 380% and energy densities of up to 3.4 J/g, using the planar mode of actuation. Recently, SRI has investigated different configurations of DE actuators that allow complex changes in surface shape and thus the creation of active surface texture. In this configuration, the "active" polymer film is bonded or coated with a thicker passive layer, such that changes in the polymer thickness during actuation of the DE device are at least partially transferred to (and often amplified by) the passive layer. Although the device gives out-of-plane motion, it can nonetheless be fabricated using two-dimensional patterning. The result is a rugged, flexible, and conformal skin that can be spatially actuated by subjecting patterned electrodes on a polymer substrate to an electric field. Using thickness-mode DE, we have demonstrated thickness changes of the order of 0.5 - 2 mm by laminating a passive elastomeric layer to a DE polymer that is only 60 μm in thickness. Such thickness changes would otherwise require a very large number of stacked layers of the DE film to produce comparable surface deformations. Preliminary pressures of 4.2 kPa (0.6 psi) in a direction normal to the plane of the DE film have been measured. However, theoretical calculations indicate that pressures of the order of 100 kPa are feasible using a single layer of DE film. Stacking multiple layers of DE film can lead to a further increase in achievable actuation pressures. Even with current levels of thickness change and actuation pressures, potential applications of such surface texture change are numerous. A thin, compliant pad made from these actuators can have a massaging or sensory augmentation function, and can be incorporated
Actuator Line Modeling of Wind Turbine Wakes
Troldborg, Niels
2009-01-01
the 3D Navier Stokes solver EllipSys3D and a LES turbulence model. Simple models, based on applying body forces in the computational domain, are developed for imposing sheared and turbulent infow and their validity is discussed. A few computations on stand alone turbines are compared to measurements...... sheared inflow shows that besides an expected vertical skewed wake the wake also becomes increasingly asymmetric in the horizontal direction as it is convected downstream. The latter phenomena, which is also often observed in measurements, is argued to be caused by the rotation of the wake. A detailed...
Model and Design of a Power Driver for Piezoelectric Stack Actuators
Chiaberge M
2010-01-01
Full Text Available A power driver has been developed to control piezoelectric stack actuators used in automotive application. An FEM model of the actuator has been implemented starting from experimental characterization of the stack and mechanical and piezoelectric parameters. Experimental results are reported to show a correct piezoelectric actuator driving method and the possibility to obtain a sensorless positioning control.
Magneto-mechanical actuation model for fin-based locomotion
Carbajal, Juan Pablo; 10.2495/DN100331
2011-01-01
In this paper, we report the results from the analysis of a numerical model used for the design of a magnetic linear actuator with applications to fin-based locomotion. Most of the current robotic fish generate bending motion using rotary motors which implies at least one mechanical conversion of the motion. We seek a solution that directly bends the fin and, at the same time, is able to exploit the magneto-mechanical properties of the fin material. This strong fin-actuator coupling blends the actuator and the body of the robot, allowing cross optimization of the system's elements. We study a simplified model of an elastic element, a spring-mass system representing a flexible fin, subjected to nonlinear forcing, emulating magnetic interaction. The dynamics of the system is studied under unforced and periodic forcing conditions. The analysis is focused on the limit cycles present in the system, which allows the periodic bending of the fin and the generation of thrust. The frequency, maximum amplitude and cente...
Modeling and Control of Electromechanical Actuators for Heavy Vehicle Applications
Pettersson, Alexander; Storm, Patrik
2012-01-01
The possibility to develop control systems for electromechanical actuators at Scania is studied, in particular the focus is on how to exchange the intelligent actuators used today with dumb ones. An intelligent actuator contains its own control electronics and computational power, bought as a unit from suppliers by Scania and controlled via the CAN bus. A dumb actuator contains no means of controlling itself and its I/O is the motor’s power pins. Intelligent actuators tend to have limited con...
Hysteresis model of magnetostrictive actuators and its numerical realization
TANG Zhi-feng; LV Fu-zai; XIANG Zhan-qin
2007-01-01
This paper presents two numerical realization of Preisach model by Density Function Method (DFM) and F Function Method (FFM) for a giant magnetostrictive actuator (GMA). Experiment and simulation showed that FFM is better than DFM for predicting precision of hysteresis loops. Lagrange bilinear interpolation algorithm is used in Preisach numerical realization to enhance prediction performance. A set of hysteresis loops and higher order reversal curves are predicted and experimentally verified. The good agreement between the measured and predicted curves shows that the classical Preisach model is effective for modelling the quasi-static hysteresis of the GMA.
Long, Yongjun; Wei, Xiaohui; Wang, Chunlei; Dai, Xin; Wang, Shigang
2014-05-01
A new rotary normal stress electromagnetic actuator for fast steering mirror (FSM) is presented. The study includes concept design, actuating torque modeling, actuator design, and validation with numerical simulation. To achieve an FSM with compact structure and high bandwidth, the actuator is designed with a cross armature magnetic topology. By introducing bias flux generated by four permanent magnets (PMs), the actuator has high-force density similar to a solenoid but also has essentially linear characteristics similar to a voice coil actuator, leading to a simply control algorithm. The actuating torque output is a linear function of both driving current and rotation angle and is formulated with equivalent magnetic circuit method. To improve modeling accuracy, both the PM flux and coil flux leakages are taken into consideration through finite element simulation. Based on the established actuator model, optimal design of the actuator is presented to meet the requirement of our FSM. Numerical simulation is then presented to validate the concept design, established actuator model, and designed actuator. It is shown that the calculated results are in a good agreement with the simulation results.
Hysteresis Modeling of Magnetic Shape Memory Alloy Actuator Based on Krasnosel'skii-Pokrovskii Model
Miaolei Zhou
2013-01-01
Full Text Available As a new type of intelligent material, magnetically shape memory alloy (MSMA has a good performance in its applications in the actuator manufacturing. Compared with traditional actuators, MSMA actuator has the advantages as fast response and large deformation; however, the hysteresis nonlinearity of the MSMA actuator restricts its further improving of control precision. In this paper, an improved Krasnosel'skii-Pokrovskii (KP model is used to establish the hysteresis model of MSMA actuator. To identify the weighting parameters of the KP operators, an improved gradient correction algorithm and a variable step-size recursive least square estimation algorithm are proposed in this paper. In order to demonstrate the validity of the proposed modeling approach, simulation experiments are performed, simulations with improved gradient correction algorithm and variable step-size recursive least square estimation algorithm are studied, respectively. Simulation results of both identification algorithms demonstrate that the proposed modeling approach in this paper can establish an effective and accurate hysteresis model for MSMA actuator, and it provides a foundation for improving the control precision of MSMA actuator.
Modeling fluid structure interaction with shape memory alloy actuated morphing aerostructures
Oehler, Stephen D.; Hartl, Darren J.; Turner, Travis L.; Lagoudas, Dimitris C.
2012-04-01
The development of efficient and accurate analysis techniques for morphing aerostructures incorporating shape memory alloys (SMAs) continues to garner attention. These active materials have a high actuation energy density, making them an ideal replacement for conventional actuation mechanisms in morphing structures. However, SMA components are often exposed to the same highly variable environments experienced by the aeroelastic assemblies into which they are incorporated. This is motivating design engineers to consider modeling fluidstructure interaction for prescribing dynamic, solution-dependent boundary conditions. This work presents a computational study of a particular morphing aerostructure with embedded, thermally actuating SMA ribbons and demonstrates the effective use of fluid-structure interaction modeling. A cosimulation analysis is utilized to determine the surface deflections and stress distributions of an example aerostructure with embedded SMA ribbons using the Abaqus Finite Element Analysis (FEA) software suite, combined with an Abaqus Computational Fluid Dynamics (CFD) processor. The global FEA solver utilizes a robust user-defined material subroutine which contains an accurate three-dimensional SMA constitutive model. Variations in the ambient fluid environment are computed using the CFD solver, and fluid pressure is mapped into surface distributed loads. Results from the analysis are qualitatively validated with independently obtained data from representative flow tests previously conducted on a physical prototype of the same aerostructure.
Fabrication, modeling and optimization of an ionic polymer gel actuator
The modeling of the electro-active behavior of ionic polymer gel is studied and the optimum conditions that maximize the deflection of the gel are investigated. The bending deformation of polymer gel under an electric field is formulated by using chemo-electro-mechanical parameters. In the modeling, swelling and shrinking phenomena due to the differences in ion concentration at the boundary between the gel and solution are considered prior to the application of an electric field, and then bending actuation is applied. As the driving force of swelling, shrinking and bending deformation, differential osmotic pressure at the boundary of the gel and solution is considered. From this behavior, the strain or deflection of the gel is calculated. To find the optimum design parameter settings (electric voltage, thickness of gel, concentration of polyion in the gel, ion concentration in the solution, and degree of cross-linking in the gel) for bending deformation, a nonlinear constrained optimization model is formulated. In the optimization model, a bending deflection equation of the gel is used as an objective function, and a range of decision variables and their relationships are used as constraint equations. Also, actuation experiments are conducted using poly(2-acrylamido-2-methylpropane sulfonic acid) (PAMPS) gel and the optimum conditions predicted by the proposed model have been verified by the experiments
Analytic model and frequency characteristics of plasma synthetic jet actuator
Zong, Hao-hua; Wu, Yun; Li, Ying-hong; Song, Hui-min; Zhang, Zhi-bo; Jia, Min
2015-02-01
This paper reports a novel analytic model of a plasma synthetic jet actuator (PSJA), considering both the heat transfer effect and the inertia of the throat gas. Both the whole cycle characteristics and the repetitive working process of PSJA can be predicted with this model. The frequency characteristics of a PSJA with 87 mm3 volume and different orifice diameters are investigated based on the analytic model combined with experiments. In the repetitive working mode, the actuator works initially in the transitional stage with 20 cycles and then in the dynamic balanced stage. During the transitional stage, major performance parameters of PSJA experience stepped growth, while during the dynamic balanced stage, these parameters are characterized by periodic variation. With a constant discharge energy of 6.9 mJ, there exists a saturated frequency of 4 kHz/6 kHz for an orifice diameter of 1 mm/1.5 mm, at which the time-averaged total pressure of the pulsed jet reaches a maximum. Between 0.5 mm and 1.5 mm, a larger orifice diameter leads to a higher saturated frequency due to the reduced jet duration time. As the actuation frequency increases, both the time-averaged cavity temperature and the peak jet velocity initially increase and then remain almost unchanged at 1600 K and 280 m/s, respectively. Besides, with increasing frequency, the mechanical energy incorporated in single pulsed jet, the expelled mass per pulse, and the time-averaged density in the cavity, decline in a stair stepping way, which is caused by the intermittent decrease of refresh stage duration in one period.
Computational Actuator Disc Models for Wind and Tidal Applications
B. Johnson
2014-01-01
Full Text Available This paper details a computational fluid dynamic (CFD study of a constantly loaded actuator disc model featuring different boundary conditions; these boundary conditions were defined to represent a channel and a duct flow. The simulations were carried out using the commercially available CFD software ANSYS-CFX. The data produced were compared to the one-dimensional (1D momentum equation as well as previous numerical and experimental studies featuring porous discs in a channel flow. The actuator disc was modelled as a momentum loss using a resistance coefficient related to the thrust coefficient (CT. The model showed good agreement with the 1D momentum theory in terms of the velocity and pressure profiles. Less agreement was demonstrated when compared to previous numerical and empirical data in terms of velocity and turbulence characteristics in the far field. These models predicted a far larger velocity deficit and a turbulence peak further downstream. This study therefore demonstrates the usefulness of the duct boundary condition (for computational ease for representing open channel flow when simulating far field effects as well as the importance of turbulence definition at the inlet.
Dynamic Actuator for Centrifuge Modeling of Soil-Structure Interaction
CABRERA, Miguel Angel; Caicedo, Bernardo; THOREL, Luc
2012-01-01
This paper presents a new dynamic actuator useful to study soil-structure interactions in a centrifuge. This new dynamic apparatus is based on an amplified piezoelectric actuator. Using this device it is possible to create vibrations in the soil sample of different frequencies and amplitudes. The dynamic actuator consists of a set of weights in a single degree of freedom system plus a piezoelectric actuator and a piezoelectric load cell, which measures the dynamic load. A description of the d...
Preisach model of hysteresis for the Piezoelectric Actuator Drive
Zsurzsan, Tiberiu-Gabriel; Andersen, Michael A. E.; Zhang, Zhe;
2015-01-01
The Piezoelectric Actuator Drive (PAD) is a precise piezoelectric motor generating high-torque rotary motion, which employs piezoelectric stack actuators in a wobblestyle actuation to generate rotation. The piezoelectric stacked ceramics used as the basis for motion in the motor suffer from...
Benard, N.; Pons-Prats, J.; Periaux, J.; Bugeda, G.; Braud, P.; Bonnet, J. P.; Moreau, E.
2016-02-01
The potential benefits of active flow control are no more debated. Among many others applications, flow control provides an effective mean for manipulating turbulent separated flows. Here, a nonthermal surface plasma discharge (dielectric barrier discharge) is installed at the step corner of a backward-facing step ( U 0 = 15 m/s, Re h = 30,000, Re θ = 1650). Wall pressure sensors are used to estimate the reattaching location downstream of the step (objective function #1) and also to measure the wall pressure fluctuation coefficients (objective function #2). An autonomous multi-variable optimization by genetic algorithm is implemented in an experiment for optimizing simultaneously the voltage amplitude, the burst frequency and the duty cycle of the high-voltage signal producing the surface plasma discharge. The single-objective optimization problems concern alternatively the minimization of the objective function #1 and the maximization of the objective function #2. The present paper demonstrates that when coupled with the plasma actuator and the wall pressure sensors, the genetic algorithm can find the optimum forcing conditions in only a few generations. At the end of the iterative search process, the minimum reattaching position is achieved by forcing the flow at the shear layer mode where a large spreading rate is obtained by increasing the periodicity of the vortex street and by enhancing the vortex pairing process. The objective function #2 is maximized for an actuation at half the shear layer mode. In this specific forcing mode, time-resolved PIV shows that the vortex pairing is reduced and that the strong fluctuations of the wall pressure coefficients result from the periodic passages of flow structures whose size corresponds to the height of the step model.
Validation of high displacement piezoelectric actuator finite element models
Taleghani, Barmac K.
2000-08-01
The paper presents the results obtained by using NASTRAN and ANSYS finite element codes to predict doming of the THUNDER piezoelectric actuators during the manufacturing process and subsequent straining due to an applied input voltage. To effectively use such devices in engineering applications, modeling and characterization are essential. Length, width, dome height, and thickness and important parameters for users of such devices. Therefore, finite element models were used to assess the effects of these parameters. NASTRAN and ANSYS used different methods for modeling piezoelectric effects. In NASTRAN, a thermal analogy was used to represent voltage at nodes as equivalent temperatures, while ANSYS processed the voltage directly using piezoelectric finite elements. The results of finite element models were validated by using the experimental results.
Validation of thermal models for a prototypical MEMS thermal actuator.
Gallis, Michail A.; Torczynski, John Robert; Piekos, Edward Stanley; Serrano, Justin Raymond; Gorby, Allen D.; Phinney, Leslie Mary
2008-09-01
This report documents technical work performed to complete the ASC Level 2 Milestone 2841: validation of thermal models for a prototypical MEMS thermal actuator. This effort requires completion of the following task: the comparison between calculated and measured temperature profiles of a heated stationary microbeam in air. Such heated microbeams are prototypical structures in virtually all electrically driven microscale thermal actuators. This task is divided into four major subtasks. (1) Perform validation experiments on prototypical heated stationary microbeams in which material properties such as thermal conductivity and electrical resistivity are measured if not known and temperature profiles along the beams are measured as a function of electrical power and gas pressure. (2) Develop a noncontinuum gas-phase heat-transfer model for typical MEMS situations including effects such as temperature discontinuities at gas-solid interfaces across which heat is flowing, and incorporate this model into the ASC FEM heat-conduction code Calore to enable it to simulate these effects with good accuracy. (3) Develop a noncontinuum solid-phase heat transfer model for typical MEMS situations including an effective thermal conductivity that depends on device geometry and grain size, and incorporate this model into the FEM heat-conduction code Calore to enable it to simulate these effects with good accuracy. (4) Perform combined gas-solid heat-transfer simulations using Calore with these models for the experimentally investigated devices, and compare simulation and experimental temperature profiles to assess model accuracy. These subtasks have been completed successfully, thereby completing the milestone task. Model and experimental temperature profiles are found to be in reasonable agreement for all cases examined. Modest systematic differences appear to be related to uncertainties in the geometric dimensions of the test structures and in the thermal conductivity of the
Thananchai Leephakpreeda
2012-01-01
Quantitative understanding of mechanical actuation of intricate Pneumatic Artificial Muscle (PAM) actuators is technically required in control system design for effective real-time implementation.This paper presents mathematical modeling of the PAM driven by hydrogen-gas pressure due to absorption and desorption of metal hydride.Empirical models of both mechanical actuation of industrial PAM and chemical reaction of the metal hydride-LaNi5 are derived systematically where their interactions comply with the continuity principle and energy balance in describing actual dynamic behaviors of the PAM actuator (PAM and hydriding/dehydriding-reaction bed).Simulation studies of mechanical actuation under various loads are conducted so as to present dynamic responses of the PAM actuators.From the promising results,it is intriguing that the heat input for the PAM actuator can be supplied to,or pumped from the reaction bed,in such a way that absorption and desorption of hydrogen gas take place,respectively,in controlling the pressure of hydrogen gas within the PAM actuator.Accordingly,this manipulation results in desired mechanical actuation of the PAM actuator in practical uses.
Vortex ring state by full-field actuator disc model
Soerensen, J.N.; Shen, W.Z.; Munduate, X. [DTU, Dept. of Energy Engineering, Lyngby (Denmark)
1997-08-01
One-dimensional momentum theory provides a simple analytical tool for analysing the gross flow behavior of lifting propellers and rotors. Combined with a blade-element strip-theory approach, it has for many years been the most popular model for load and performance predictions of wind turbines. The model works well at moderate and high wind velocities, but is not reliable at small wind velocities, where the expansion of the wake is large and the flow field behind the rotor dominated by turbulent mixing. This is normally referred to as the turbulent wake state or the vortex ring state. In the vortex ring state, momentum theory predicts a decrease of thrust whereas the opposite is found from experiments. The reason for the disagreement is that recirculation takes place behind the rotor with the consequence that the stream tubes past the rotor becomes effectively chocked. This represents a condition at which streamlines no longer carry fluid elements from far upstream to far downstream, hence one-dimensional momentum theory is invalid and empirical corrections have to be introduced. More sophisticated analytical or semi-analytical rotor models have been used to describe stationary flow fields for heavily loaded propellers. In recent years generalized actuator disc models have been developed, but up to now no detailed computations of the turbulent wake state or the vortex ring state have been performed. In the present work the phenomenon is simulated by direct simulation of the Navier-Stokes equations, where the influence of the rotor on the flow field is modelled simply by replacing the blades by an actuator disc with a constant normal load. (EG) 13 refs.
Realtime Surface Shear Stress Control with MEMS Sensors/Actuators in Turbulent Boundary Layers
Huang, Adam; Lew, James; Ho, Chih-Ming; Xu, Yong; Tai, Yu-Chong
2003-11-01
High-speed surface streaks in turbulent boundary layers have been attributed to approximately 40friction drag. A real-time control system for reducing surface shear stress has being developed. The system consists of two linear arrays of MEMS surface shear stress imagers for providing control and feedback measurements and a recently developed, micro-machined flap-type actuator for interaction with the streak structures. Driven by a constant temperature anemometry circuit with an overheat ratio of 12sensitivity of 100 mV/Pa and frequency response of 20 kHz. The micro-machined bubble-flap actuator is essentially a thin silicon cantilever beam which hangs/sits on top of a silicone diaphragm molded into a bulk etched silicon cavity. The flap shape used is a 3mm long (streamwise) by 1mm wide rectangular beam, with a thickness of 40 um. Actuation is achieved by pneumatically inflating the silicone diaphragm, which then pushes up the silicon beam. The current flap can achieve off-plane deflections of over 130 um at frequencies up to 150 Hz, with a rise time of 2ms and a fall time of 4ms. Experiments are carried out with the system installed onto the wall of a 2-D turbulent wind tunnel. At Re 10k, corresponding to flow velocity of 10 m/s, time-averaged reduction of 4achieved continuous actuation at 130 um and 150 Hz. Furthermore, in offline data processing, it has been found that the actuator interacting with the streak structures has reduce the peak shear stress of a streak by an additional 0.2 Pa, or about 50
Joseph I. Cline
2010-04-22
A novel hypothesized detection scheme for the detection of chemical agents was proposed: SAPS ``Surface-Adsorbed Polarization Sensors''. In this technique a thin layer of molecular rotors is adsorbed to a surface. The rotors can be energized by light absorption, but are otherwise locked in position or alternatively rotate slowly. Using polarized light, the adsorbed rotors are turned as an ensemble. Chemical agent (analyte) binding that alters the rotary efficiency would be detected by sensitive polarized absorption techniques. The mechanism of the SAPS detection can be mechanical, chemical, or photochemical: only a change in rotary efficiency is required. To achieve the goal of SAPS detection, new spectroscopic technique, polarized Normal Incidence Cavity Ringdown Spectroscopy (polarized NICRDS), was developed. The technique employs very sensitive and general Cavity Ringdown absorption spectroscopy along with the ability to perform polarized absorption measurements. Polarized absorption offers the ability to measure the angular position of molecular chromophores. In the new experiments a thin layer of SAPS sensors (roughly corresponding to a monolayer coverage on a surface) immobilized in PMMA. The PMMA layer is less than 100~nm thick and is spin-coated onto a flat fused-silica substrate. The new technique was applied to study the photoisomerization-driven rotary motion of a family of SAPS actuators based on a family of substituted dibenzofulvene rotors based upon 9-(2,2,2- triphenylethylidene)fluorene. By varying the substitution to include moieties such as nitro, amino, and cyano the absorption spectrum and the quantum efficiency of photoisomerization can be varied. This SAPS effect was readily detected by polarized NICRDS. The amino substituted SAPS actuator binds H+ to form an ammonium species which was shown to have a much larger quantum efficiency for photoisomerization. A thin layer of immobilized amino actuators were then shown by polarized NICRDS
Schwartz, Robert W.; Ballato, J.; Northwang, W. D.; Laoratanakul, P.
2000-01-01
Dome formation in Rainbow and Thunder actuators occurs to relieve thermal expansion mismatch stress between the metallic and piezoelectric layers during cooling from device fabrication temperatures. Accompanying this process is the generation of an internal stress profile within the devices and the development of significant tensile stresses within the surface region of the piezoelectric. These tensile stresses affect the domain configuration (ratio of c-to-a domains), and improve the 90 deg. domain wall movement response of the device in this region of the piezoelectric. This results in improved electromechanical performance compared to standard direct extensional and flextensional devices, presumably because of the contributions of stress to the non-linearity of the piezoelectric d-coefficients. 1 Interestingly, this improvement in response seems counterintuitive; a stress perpendicular to the direction of the applied electric field should impede, not contribute to 90' domain switching. Further consideration of the lower region of the piezoelectric that is under compressive stress thus appears warranted. The specified objectives of the research were to: 1. Conduct finite element and equivalent circuit simulation-based investigations to understand the effects of actuator geometry on internal stress distribution and actuator performance (displacement and load-bearing capabilities). 2. Use the results of the modeling studies to predict the processing conditions (geometry and thickness ratio) required for the fabrication of Rainbow ceramics with optimized performance.
Laser-induced novel patterns: As smart strain actuators for new-age dental implant surfaces
Highlights: ► It is time for that paradigm shift and for an exploration of novel surfaces. ► We developed novel 3D smart surfaces as strain actuators by nanosecond laser pulse energies. ► We analyzed these smart surface morphologies using FEM. ► We estimated their internal stiffness values which play a great role on stress shielding effect. ► We gave the optimum operation parameters. - Abstract: Surface morphologies of titanium implants are of crucial importance for long-term mechanical adaptation for following implantation. One major problem is the stress shielding effect which originates from the mismatch of the bone and the implant elasticity. It is time for a paradigm shift and for an exploration of novel smart surfaces to prevent this problem. Several surface treatment methods have traditionally been used to modify the surface morphology of titanium dental implants. The laser micro-machining can be considered as a unique and promising, non-contact, no media, contamination free, and flexible treatment method for modifying surface properties of materials in the biomedical industry. The aim of the present study is two folds; to develop novel 3D smart surfaces which can be acted as strain actuators by nanosecond laser pulse energies and irradiation strategies. And analyze these smart surface morphologies using finite element methods in order to estimate their internal stiffness values which play a great role on stress shielding effect. Novel 3D smart strain actuators were prepared using an ytterbium fiber laser (λ = 1060 nm) with 200–250 ns pulse durations on commercial pure titanium dental implant material specimen surfaces and optimum operation parameters were suggested.
Laser-induced novel patterns: As smart strain actuators for new-age dental implant surfaces
Celen, Serap, E-mail: serap.celen@ege.edu.tr [Ege University, Faculty of Engineering, Mechanical Engineering Department, Izmir, 35100 (Turkey); Oezden, Hueseyin [Ege University, Faculty of Engineering, Mechanical Engineering Department, Izmir, 35100 (Turkey)
2012-12-15
Highlights: Black-Right-Pointing-Pointer It is time for that paradigm shift and for an exploration of novel surfaces. Black-Right-Pointing-Pointer We developed novel 3D smart surfaces as strain actuators by nanosecond laser pulse energies. Black-Right-Pointing-Pointer We analyzed these smart surface morphologies using FEM. Black-Right-Pointing-Pointer We estimated their internal stiffness values which play a great role on stress shielding effect. Black-Right-Pointing-Pointer We gave the optimum operation parameters. - Abstract: Surface morphologies of titanium implants are of crucial importance for long-term mechanical adaptation for following implantation. One major problem is the stress shielding effect which originates from the mismatch of the bone and the implant elasticity. It is time for a paradigm shift and for an exploration of novel smart surfaces to prevent this problem. Several surface treatment methods have traditionally been used to modify the surface morphology of titanium dental implants. The laser micro-machining can be considered as a unique and promising, non-contact, no media, contamination free, and flexible treatment method for modifying surface properties of materials in the biomedical industry. The aim of the present study is two folds; to develop novel 3D smart surfaces which can be acted as strain actuators by nanosecond laser pulse energies and irradiation strategies. And analyze these smart surface morphologies using finite element methods in order to estimate their internal stiffness values which play a great role on stress shielding effect. Novel 3D smart strain actuators were prepared using an ytterbium fiber laser ({lambda} = 1060 nm) with 200-250 ns pulse durations on commercial pure titanium dental implant material specimen surfaces and optimum operation parameters were suggested.
Modeling of thermo-mechanical fatigue and damage in shape memory alloy axial actuators
Wheeler, Robert W.; Hartl, Darren J.; Chemisky, Yves; Lagoudas, Dimitris C.
2015-04-01
The aerospace, automotive, and energy industries have seen the potential benefits of using shape memory alloys (SMAs) as solid state actuators. Thus far, however, these actuators are generally limited to non-critical components or over-designed due to a lack of understanding regarding how SMAs undergo thermomechanical or actuation fatigue and the inability to accurately predict failure in an actuator during use. The purpose of this study was to characterize the actuation fatigue response of Nickel-Titanium-Hafnium (NiTiHf) axial actuators and, in turn, use this characterization to predict failure and monitor damage in dogbone actuators undergoing various thermomechanical loading paths. Calibration data was collected from constant load, full cycle tests ranging from 200-600MPa. Subsequently, actuator lifetimes were predicted for four additional loading paths. These loading paths consisted of linearly varying load with full transformation (300-500MPa) and step loads which transition from zero stress to 300-400MPa at various martensitic volume fractions. Thermal cycling was achieved via resistive heating and convective cooling and was controlled via a state machine developed in LabVIEW. A previously developed fatigue damage model, which is formulated such that the damage accumulation rate is general in terms of its dependence on current and local stress and actuation strain states, was utilized. This form allows the model to be utilized for specimens undergoing complex loading paths. Agreement between experiments and simulations is discussed.
Modeling and development of a twisting wing using inductively heated shape memory alloy actuators
Saunders, Robert N.; Hartl, Darren J.; Boyd, James G.; Lagoudas, Dimitris C.
2015-04-01
Wing twisting has been shown to improve aircraft flight performance. The potential benefits of a twisting wing are often outweighed by the mass of the system required to twist the wing. Shape memory alloy (SMA) actuators repeatedly demonstrate abilities and properties that are ideal for aerospace actuation systems. Recent advances have shown an SMA torsional actuator that can be manufactured and trained with the ability to generate large twisting deformations under substantial loading. The primary disadvantage of implementing large SMA actuators has been their slow actuation time compared to conventional actuators. However, inductive heating of an SMA actuator allows it to generate a full actuation cycle in just seconds rather than minutes while still . The aim of this work is to demonstrate an experimental wing being twisted to approximately 10 degrees by using an inductively heated SMA torsional actuator. This study also considers a 3-D electromagnetic thermo-mechanical model of the SMA-wing system and compare these results to experiments to demonstrate modeling capabilities.
Minami Takato
2014-07-01
Full Text Available Micro-robotic systems are increasingly used in medicine and other fields requiring precision engineering. This paper proposes a piezoelectric impact- type rotary actuator and applies it to a millimetre-size robot controlled by a hardware neuron model. The rotary actuator and robot are fabricated by micro-electro- mechanical systems (MEMS technology. The actuator is composed of multilayer piezoelectric elements. The rotational motion of the rotor is generated by the impact head attached to the piezoelectric element. The millimetre-size robot is fitted with six legs, three on either side of the developed actuator, and can walk on uneven surfaces like an insect. The three leg parts on each side are connected by a linking mechanism. The control system is a hardware neuron model constructed from analogue electronic circuits that mimic the behaviour of biological neurons. The output signal ports of the controller are connected to the multilayer piezoelectric element. This robot system requires no specialized software programs or A/D converters. The rotation speed of the rotary actuator reaches 60 rpm at an applied neuron frequency of 25 kHz during the walking motion. The width, length and height of the robot are 4.0, 4.6 and 3.6 mm, respectively. The motion speed is 180 mm/min.
Tian, Pengfei; Jones, Richard W.; Yu, Fei
2016-07-01
A dielectric elastomer (DE) tubular actuator, based on compliant metal electrode technology, exhibits hysteresis-like characteristics when driven with a low power rated high voltage power supply (HVPS). This behavior occurs mainly because the DE actuator acts as a capacitive load compromising the ‘slew rate’ of the HVPS during the actuator’s operation. The motivation of this contribution is to investigate the use of elliptical modelling approaches for capturing the hysteresis characteristics exhibited by the DE tubular actuator when it is driven by a low cost low power rated HVPS. The DE tubular actuator considered in this work demonstrates asymmetric hysteresis behaviour due to the nonlinear voltage–strain behaviour of the actuator. A linearization filter placed in series with the actuator (during its operation) ensures a symmetric hysteresis characteristic that can then be modelled using an ellipse-based approach. Elliptical models come in many forms with the two most popular being the constrained general conic form and the general parametric form. Elliptical-based hysteresis model fits are carried out on experimental data obtained from the application of periodic input voltages, at a number of different low-frequencies, to the tubular actuator. The range of frequencies used is related to the possible use of the tubular actuator for attenuating low frequency vibration during DE actuator-based load positioning applications. Constrained conic and general parametric forms of elliptical model are used for modelling the hysteresis characteristics of the DE actuator and rate dependent models developed based on both approaches. The sensitivity of both of these rate dependent models to small inaccuracies in model parameters was then investigated. The general parametric form was found to be more robust in this respect.
Actuator line modeling of vertical-axis turbines
Bachant, Peter; Wosnik, Martin
2016-01-01
To bridge the gap between high and low fidelity numerical modeling tools for vertical-axis (or cross-flow) turbines (VATs or CFTs), an actuator line model (ALM) was developed and validated for both a high and a medium solidity vertical-axis turbine at rotor diameter Reynolds numbers $Re_D \\sim 10^6$. The ALM is a hybridization of classical blade element theory with Navier--Stokes based flow models, and in this study both $k$--$\\epsilon$ Reynolds-averaged Navier--Stokes (RANS) and Smagorinsky large eddy simulation (LES) turbulence models were tested. The RANS models were able to be run on coarse grids while still providing good convergence behavior in terms of the mean power coefficient, and also approximately four orders of magnitude reduction in computational expense compared with 3-D blade-resolved RANS simulations. Submodels for dynamic stall, end effects, added mass, and flow curvature were implemented, resulting in reasonable performance predictions for the high solidity rotor, more discrepancies for the...
Laser-induced novel patterns: As smart strain actuators for new-age dental implant surfaces
Çelen, Serap; Özden, Hüseyin
2012-12-01
Surface morphologies of titanium implants are of crucial importance for long-term mechanical adaptation for following implantation. One major problem is the stress shielding effect which originates from the mismatch of the bone and the implant elasticity. It is time for a paradigm shift and for an exploration of novel smart surfaces to prevent this problem. Several surface treatment methods have traditionally been used to modify the surface morphology of titanium dental implants. The laser micro-machining can be considered as a unique and promising, non-contact, no media, contamination free, and flexible treatment method for modifying surface properties of materials in the biomedical industry. The aim of the present study is two folds; to develop novel 3D smart surfaces which can be acted as strain actuators by nanosecond laser pulse energies and irradiation strategies. And analyze these smart surface morphologies using finite element methods in order to estimate their internal stiffness values which play a great role on stress shielding effect. Novel 3D smart strain actuators were prepared using an ytterbium fiber laser (λ = 1060 nm) with 200-250 ns pulse durations on commercial pure titanium dental implant material specimen surfaces and optimum operation parameters were suggested.
Nishino, Takafumi
2012-01-01
Modelling of turbine blade-induced turbulence (BIT) is discussed within the framework of three-dimensional Reynolds-averaged Navier-Stokes (RANS) actuator disk computations. We first propose a generic (baseline) BIT model, which is applied only to the actuator disk surface, does not include any model coefficients (other than those used in the original RANS turbulence model) and is expected to be valid in the limiting case where BIT is fully isotropic and in energy equilibrium. The baseline model is then combined with correction functions applied to the region behind the disk to account for the effect of rotor tip vortices causing a mismatch of Reynolds shear stress between short- and long-time averaged flow fields. Results are compared with wake measurements of a two-bladed wind turbine model of Medici and Alfredsson [Wind Energy, Vol. 9, 2006, pp. 219-236] to demonstrate the capability of the new model.
Roiter, Yuri; Minko, Iryna; Nykypanchuk, Dmytro; Tokarev, Ihor; Minko, Sergiy
2011-12-01
The mechanism of nanoparticle actuation by stimuli-responsive polymer brushes triggered by changes in the solution pH was discovered and investigated in detail in this study. The finding explains the high spectral sensitivity of the composite ultrathin film composed of a poly(2-vinylpyridine) (P2VP) brush that tunes the spacing between two kinds of nanoparticles--gold nanoislands immobilized on a transparent support and gold colloidal particles adsorbed on the brush. The optical response of the film relies on the phenomenon of localized surface plasmon resonances in the noble metal nanoparticles, giving rise to an extinction band in visible spectra, and a plasmon coupling between the particles and the islands that has a strong effect on the band position and intensity. Since the coupling is controlled by the interparticle spacing, the pH-triggered swelling-shrinking transition in the P2VP brush leads to pronounced changes in the transmission spectra of the hybrid film. It was not established in the previous publications how the actuation of gold nanoparticles within a 10-15 nm interparticle distance could result in the 50-60 nm shift in the absorbance maximum in contrast to the model experiments and theoretical estimations of several nanometer shifts. In this work, the extinction band was deconvoluted into four spectrally separated and overlapping contributions that were attributed to different modes of interactions between the particles and the islands. These modes came into existence due to variations in the thickness of the grafted polymeric layer on the profiled surface of the islands. In situ atomic force microscopy measurements allowed us to explore the behavior of the Au particles as the P2VP brush switched between the swollen and collapsed states. In particular, we identified an interesting, previously unanticipated regime when a particle position in a polymer brush was switched between two distinct states: the particle exposed to the surface of the
A modeling framework for deteriorating control system and predictive maintenance of actuators
Actuators play a central role in industrial automation systems. They are costly, and therefore studying their dependability needs all attention. Usually, an actuator is inserted in a feedback control system, and its mission is to implement a control action delivered by a controller. In this paper, a monotonic actuator deterioration is considered and it is assumed that a relationship exists between the control action and the physical actuator's deterioration. A modeling framework is proposed including a non-decreasing stochastic degradation process driving the inability for an actuator to fully implement its role. The prognosis of the actuator's residual useful lifetime is derived and used to update the controller's setting. The controller reconfiguration completes the maintenance corrective and preventive actions. This new action is suggested as an alternative for maintenance strategy. - Highlights: • A degrading control system model is proposed focusing on actuator deterioration. • It is assumed a relationship between this degradation and its loss of efficiency. • The actuator RUL is quantified as a quantile of its conditional survival function. • RUL prognosis is used to reconfigure the control input law. • This new action is suggested as an alternative for maintenance strategy
Modeling posture-dependent leg actuation in sagittal plane locomotion
Schmitt, J [Department of Mechanical Engineering, Oregon State University, Corvallis, OR 97331 (United States); Clark, J, E-mail: schmitjo@engr.orst.ed [Department of Mechanical Engineering, Florida State University, Tallahassee, FL 32310 (United States)
2009-12-15
The spring loaded inverted pendulum template has been shown to accurately model the steady locomotion dynamics of a variety of running animals, and has served as the inspiration for an entire class of dynamic running robots. While the template models the leg dynamics by an energy-conserving spring, insects and animals have structures that dissipate, store and produce energy during a stance phase. Recent investigations into the spring-like properties of limbs, as well as animal response to drop-step perturbations, suggest that animals use their legs to manage energy storage and dissipation, and that this management is important for gait stability. In this paper, we extend our previous analysis of control of the spring loaded inverted pendulum template via changes in the leg touch-down angle to include energy variations during the stance phase. Energy variations are incorporated through leg actuation that varies the force-free leg length during the stance phase, yet maintains qualitatively correct force and velocity profiles. In contrast to the partially asymptotically stable gaits identified in previous analyses, incorporating energy and leg angle variations in this manner produces complete asymptotic stability. Drop-step perturbation simulations reveal that the control strategy is rather robust, with gaits recovering from drops of up to 30% of the nominal hip height.
Modeling posture-dependent leg actuation in sagittal plane locomotion
The spring loaded inverted pendulum template has been shown to accurately model the steady locomotion dynamics of a variety of running animals, and has served as the inspiration for an entire class of dynamic running robots. While the template models the leg dynamics by an energy-conserving spring, insects and animals have structures that dissipate, store and produce energy during a stance phase. Recent investigations into the spring-like properties of limbs, as well as animal response to drop-step perturbations, suggest that animals use their legs to manage energy storage and dissipation, and that this management is important for gait stability. In this paper, we extend our previous analysis of control of the spring loaded inverted pendulum template via changes in the leg touch-down angle to include energy variations during the stance phase. Energy variations are incorporated through leg actuation that varies the force-free leg length during the stance phase, yet maintains qualitatively correct force and velocity profiles. In contrast to the partially asymptotically stable gaits identified in previous analyses, incorporating energy and leg angle variations in this manner produces complete asymptotic stability. Drop-step perturbation simulations reveal that the control strategy is rather robust, with gaits recovering from drops of up to 30% of the nominal hip height.
Theoretical modeling of pulse discharge cycle in dielectric barrier discharge plasma actuator
Sato, Shintaro; Ohnishi, Naofumi
2016-07-01
Simple models based on two-dimensional simulations are proposed to estimate intervals of periodically observed current pulses with a positive-going voltage in a dielectric barrier discharge plasma actuator. There are two distinct peaks in one streamer discharge; one is related to the formation of an ion cloud and the other is related to a filamentary discharge that is identified as a streamer. Simulation results show that the intervals of the current pulses depend on the slope of the applied voltage. For the ion-cloud formation phase, we model the time evolution of electron number density at the exposed electrode with ionization frequency. For the ion-cloud expansion phase, a positive ion cylinder model is proposed to estimate the electric field generated by surface charge on the dielectric. These models well reproduce the discharge intervals obtained in the numerical simulations.
Dynamic actuator for Soil-Structure Interaction physical modelling in centrifuge
CABRERA, Miguel; Caicedo, Bernardo; THOREL, Luc
2014-01-01
Dynamic interactions in centrifuge modelling are often induced with external or not controlled sources. This paper presents a method to study Soil-Structure Interaction in centrifuge, with the use of a dynamic actuator developed for centrifuge testing. The dynamic actuator is employed into the model giving the possibility to test the dynamic response of a wind turbine structure, without any additional supporting accessory. The centrifuge soil model was instrumented in order to measure the wav...
Modelling of Moving Coil Actuators in Fast Switching Valves Suitable for Digital Hydraulic Machines
Nørgård, Christian; Roemer, Daniel Beck; Bech, Michael Møller
2015-01-01
The efficiency of digital hydraulic machines is strongly dependent on the valve switching time. Recently, fast switching have been achieved by using a direct electromagnetic moving coil actuator as the force producing element in fast switching hydraulic valves suitable for digital hydraulic...... machines. Mathematical models of the valve switching, targeted for design optimisation of the moving coil actuator, are developed. A detailed analytical model is derived and presented and its accuracy is evaluated against transient electromagnetic finite element simulations. The model includes an...
Determining the optimal smoothing length scale for actuator line models of wind turbine blades
Martinez, Luis; Meneveau, Charles
2015-11-01
The actuator line model (ALM) is a widely used tool for simulating wind turbines when performing Large-Eddy Simulations. The ALM uses a smearing kernel ηɛ = 1 /ɛ3π 3 / 2 exp (-r2 /ɛ2) , where r is the distance to an actuator point, and ɛ is the smoothing length scale which establishes the kernel width, to project the lift and drag forces onto the grid. In this work, we develop formulations to establish the optimum value of the smoothing length scale ɛ, based on physical arguments, instead of purely numerical constraints. This parameter has a very important role in the ALM, to provide a length scale, which may, for example, be related to the chord of the airfoil being studied. In the proposed approach, we compare features (such as vertical pressure gradient) of a potential flow solution for flow over a lifting surface with features of the solution of the Euler equations with a body force term. The potential flow solution over a lifting surface is used as a general representation of an airfoil. The method presented aims to minimize the difference between these features of the flow fields as a function of the smearing length scale (ɛ), in order to obtain the optimum value. This work is supported by NSF (IGERT and IIA-1243482) and computations use XSEDE resources.
As a powerful method to reduce actuation voltage in an electrostatic micro-actuator, we propose and investigate an electrostatic micro-actuator with a pre-charged series capacitor. In contrast to a conventional electrostatic actuator, the injected pre-charges into the series capacitor can freely modulate the pull-in voltage of the proposed actuator even after the completion of fabrication. The static characteristics of the proposed actuator were investigated by first developing analytical models based on a parallel-plate capacitor model. We then successfully designed and demonstrated a micro-switch with a pre-charged series capacitor. The pull-in voltage of the fabricated micro-switch was reduced from 65.4 to 0.6 V when pre-charged with 46.3 V. The on-resistance of the fabricated micro-switch was almost the same as the initial one, even when the device was pre-charged, which was demonstrated for the first time. All results from the analytical models, finite element method simulations, and measurements were in good agreement with deviations of less than 10%. This work can be favorably adapted to electrostatic micro-switches which need a low actuation voltage without noticeable degradation of performance. (paper)
From Beetles in Nature to the Laboratory: Actuating Underwater Locomotion on Hydrophobic Surfaces.
Pinchasik, Bat-El; Steinkühler, Jan; Wuytens, Pieter; Skirtach, Andre G; Fratzl, Peter; Möhwald, Helmuth
2015-12-29
The controlled wetting and dewetting of surfaces is a primary mechanism used by beetles in nature, such as the ladybird and the leaf beetle for underwater locomotion.1 Their adhesion to surfaces underwater is enabled through the attachment of bubbles trapped in their setae-covered legs. Locomotion, however, is performed by applying mechanical forces in order to move, attach, and detach the bubbles in a controlled manner. Under synthetic conditions, however, when a bubble is bound to a surface, it is nearly impossible to maneuver without the use of external stimuli. Thus, actuated wetting and dewetting of surfaces remain challenges. Here, electrowetting-on-dielectric (EWOD) is used for the manipulation of bubble-particle complexes on unpatterned surfaces. Bubbles nucleate on catalytic Janus disks adjacent to a hydrophobic surface. By changing the wettability of the surface through electrowetting, the bubbles show a variety of reactions, depending on the shape and periodicity of the electrical signal. Time-resolved (μs) imaging of bubble radial oscillations reveals possible mechanisms for the lateral mobility of bubbles on a surface under electrowetting: bubble instability is induced when electric pulses are carefully adjusted. This instability is used to control the surface-bound bubble locomotion and is described in terms of the change in surface energy. It is shown that a deterministic force applied normal can lead to a random walk of micrometer-sized bubbles by exploiting the phenomenon of contact angle hysteresis. Finally, bubble use in nature for underwater locomotion and the actuated bubble locomotion presented in this study are compared. PMID:26633751
Stuebner, Michael; Smith, Ralph C.
2010-04-01
Macro Fiber Composite (MFC) actuators utilize PZT fibers embedded in an epoxy matrix for structural actuation. Due to their construction, they are lightweight and provide broadband inputs. Significant advantages of MFC actuators are their high performance, durability, and flexibility when compared to traditional piezoceramic actuators. They are presently being considered for a range of applications including positioning of membrane mirrors and structural control in the aerospace and automotive industry. However, they exhibit varying degrees of hysteresis and constitutive nonlinearities throughout their operating range that must be incorporated in models to achieve the full capabilities of the materials. In this paper, hysteresis is modeled using the homogenized energy model. The inverse model is then used to construct an inverse compensator framework suitable for subsequent control design. The performance of the inverse compensator is illustrated through a numerical example.
Post-buckled precompressed subsonic micro-flight control actuators and surfaces
Barrett, Ron; Vos, Roelof
2008-10-01
This paper describes a new class of flight control actuators using post-buckled precompressed (PBP) piezoelectric elements to provide much improved actuator performance. These PBP actuator elements are modeled using basic large deflection Euler-beam estimations accounting for laminated plate effects. The deflection estimations are then coupled to a high rotation kinematic model which translates PBP beam bending to stabilator deflections. A test article using PZT-5H piezoceramic sheets built into an active bender element was fitted with an elastic band which induced much improved deflection levels. Statically the bender element was capable of producing unloaded end rotations on the order of ± 2.6°. With axial compression, the end deflections were shown to increase nearly four-fold. The PBP element was then fitted with a graphite-epoxy aeroshell which was designed to pitch around a tubular stainless steel main spar. Quasi-static bench testing showed excellent correlation between theory and experiment through ± 25° of pitch deflection. Finally, wind tunnel testing was conducted at airspeeds up to 120 kts (62 m s-1, 202 ft s-1). Testing showed that deflections up to ± 20° could be maintained at even the highest flight speed. The stabilator showed no flutter or divergence tendencies at all flight speeds. At higher deflection levels, it was shown that a slight degradation deflection was induced by nose-down pitching moments generated by separated flow conditions induced by extremely high angles of attack.
Post-buckled precompressed (PBP) subsonic micro flight control actuators and surfaces
Barrett, Ron; Vos, Roelof; De Breuker, Roeland
2007-04-01
This paper describes a new class of flight control actuators using Post-Buckled Precompressed (PBP) piezoelectric elements to provide much improved actuator performance. These PBP actuator elements are modeled using basic large deflection Euler-beam estimations accounting for laminated plate effects. The deflection estimations are then coupled to a high rotation kinematic model which translates PBP beam bending to stabilator deflections. A test article using PZT-5H piezoceramic sheets built into an active bender element was fitted with an elastic band which induced much improved deflection levels. Statically the bender element was capable of producing unloaded end rotations on the order of +/-2.6°. With axial compression, the end deflections were shown to increase nearly 4-fold. The PBP element was then fitted with a graphite-epoxy aeroshell which was designed to pitch around a tubular stainless steel main spar. Quasi-static bench testing showed excellent correlation between theory and experiment through +/-25° of pitch deflection. Finally, wind tunnel testing was conducted at airspeeds up to 120kts (62m/s, 202ft/s). Testing showed that deflections up through +/-20° could be maintained at even the highest flight speed. The stabilator showed no flutter or divergence tendencies at all flight speeds. At higher deflection levels, it was shown that a slight degradation deflection was induced by nose-down pitching moments generated by separated flow conditions induced by extremely high angles of attack.
The effect of plasma actuator on the depreciation of the aerodynamic drag on box model
Harinaldi, Budiarso, Julian, James; Rabbani M., N.
2016-06-01
Recent active control research advances have provided many benefits some of which in the field of transportation by land, sea as well as by air. Flow engineering by using active control has proven advantages in energy saving significantly. One of the active control equipment that is being developed, especially in the 21st century, is a plasma actuator, with the ability to modify the flow of fluid by the approach of ion particles makes these actuators a very powerful and promising tool. This actuator can be said to be better to the previously active control such as suction, blowing and synthetic jets because it is easier to control, more flexible because it has no moving parts, easy to be manufactured and installed, and consumes a small amount of energy with maximum capability. Plasma actuator itself is the composition of a material composed of copper and a dielectric sheet, where the copper sheets act as an electricity conductor and the dielectric sheet as electricity insulator. Products from the plasma actuators are ion wind which is the result of the suction of free air around the actuator to the plasma zone. This study investigates the ability of plasma actuators in lowering aerodynamic drag which is commonly formed in the models of vehicles by varying the shape of geometry models and the flow speed.
Modeling and control of a hydraulically actuated flexible-prismatic link robot
Most of the research related to flexible link manipulators to date has focused on single link, fixed length, single plane of vibration test beds. In addition, actuation has been predominantly based upon electromagnetic motors. Ironically, these elements are rarely found in the existing industrial long reach systems. This manuscript describes a new hydraulically actuated, long reach manipulator with a flexible prismatic link at Oak Ridge National Laboratory (ORNL). Focus is directed towards both modeling and control of hydraulic actuators as well as flexible links that have variable natural frequencies
Modeling and control of a hydraulically actuated flexible-prismatic link robot
Love, L.; Kress, R.; Jansen, J.
1996-12-01
Most of the research related to flexible link manipulators to date has focused on single link, fixed length, single plane of vibration test beds. In addition, actuation has been predominantly based upon electromagnetic motors. Ironically, these elements are rarely found in the existing industrial long reach systems. This manuscript describes a new hydraulically actuated, long reach manipulator with a flexible prismatic link at Oak Ridge National Laboratory (ORNL). Focus is directed towards both modeling and control of hydraulic actuators as well as flexible links that have variable natural frequencies.
Piezoelectric Composite Actuators: Modelling of the Static and Dynamic Behaviour
Wiwattananon, P.
2013-01-01
Smart actuators, made of smart materials, are becoming more attractive in many applications because smart materials are not subjected to wear and does not require lubrication during services. Piezoelectric materials are a group of the many attractive smart materials that are being investigated for m
Computer Modeling of Selected Fault Regimes of DC Actuators
Doležel, Ivo; Dvořák, P.; Mach, M.; Ulrych, B.
Sydney: The University of Newcastle, 2004, s. 529-534. [IFAC Symposium on Mechatronic Systems /3./. Sydney (AU), 06.09.2004-08.09.2004] R&D Projects: GA MŠk(CZ) LN00B084 Institutional research plan: CEZ:AV0Z2057903 Keywords : actuators * electromagnetic fields * temperature calculations Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering
Design Optimization Tool for Synthetic Jet Actuators Using Lumped Element Modeling
Gallas, Quentin; Sheplak, Mark; Cattafesta, Louis N., III; Gorton, Susan A. (Technical Monitor)
2005-01-01
The performance specifications of any actuator are quantified in terms of an exhaustive list of parameters such as bandwidth, output control authority, etc. Flow-control applications benefit from a known actuator frequency response function that relates the input voltage to the output property of interest (e.g., maximum velocity, volumetric flow rate, momentum flux, etc.). Clearly, the required performance metrics are application specific, and methods are needed to achieve the optimal design of these devices. Design and optimization studies have been conducted for piezoelectric cantilever-type flow control actuators, but the modeling issues are simpler compared to synthetic jets. Here, lumped element modeling (LEM) is combined with equivalent circuit representations to estimate the nonlinear dynamic response of a synthetic jet as a function of device dimensions, material properties, and external flow conditions. These models provide reasonable agreement between predicted and measured frequency response functions and thus are suitable for use as design tools. In this work, we have developed a Matlab-based design optimization tool for piezoelectric synthetic jet actuators based on the lumped element models mentioned above. Significant improvements were achieved by optimizing the piezoceramic diaphragm dimensions. Synthetic-jet actuators were fabricated and benchtop tested to fully document their behavior and validate a companion optimization effort. It is hoped that the tool developed from this investigation will assist in the design and deployment of these actuators.
Rossi, C.; Esteve, D.; Temple-Boyer, P. [Centre National d`Etudes Spatiales (CNES), 31 - Toulouse (France). Laboratoire d`Analyse et d`Architecture des Systemes; Delannoy, G. [SNPE-CRB, 91 - Vert-le-Petit (France)
1997-09-01
In this paper, we present a new way to perform actuation through the use of forces produced by pyrotechnic combustion. After describing the functioning, of this so-called pyrotechnic actuator, we present the modelling of the combustion ignition in order to find an optimal ignition system enabling to minimize energy. Good agreement between experience and simulation is obtained and characterizations of the pyrotechnic actuator give an idea of its performances in terms of gas yield and forces developed. The low cost and the use of a classic micro-technology process as well as the excellent ratio between the energy produced over the power consumption give good perspectives for these actuators. (authors) 11 refs.
FLUTTER SUPPRESSION USING DISTRIBUTEDPIEZOELECTRIC ACTUATORS
无
2000-01-01
A piezoelectric actuator has the benefits of flexibility of its position, without time lag and wide bandpass characteristics. The early results of the wind tunnel flutter suppression test using the piezoeletric actuator were presented in Ref.［1］. A rigid rectangular wing model is constrained by a plunge spring and a pitch spring, and a pair of piezoelectric actuators is bonded on both sides of the plunge spring so as to carry out the active control. Refs.［2,3］ reported two flutter suppression wind tunnel tests where the distributed piezoelectric actuators were used. In Ref.［2］ low speed wind tunnel tests were conducted with aluminum and composite plate-like rectangular models fully covered by piezoelectric actuators. Flutter speed is increased by 11%. In Ref.［3］ a composite plate-like swept back model with piezoceramic actuators bonded on the inboard surface was tested in a transonic wind tunnel and a 12% increment of flutter dynamic pressure was achieved. In the present investigation, an aluminum plate-like rectangular model with inboard bonded piezoceramic actuators is adopted. Active flutter suppression control law has been designed. A series of analyses and ground tests and, finally, low-speed wind tunnel tests with the active control system opened and closed are conducted. Reasonable results have been obtained.
Final report : compliant thermo-mechanical MEMS actuators, LDRD #52553.
Walraven, Jeremy Allen; Baker, Michael Sean; Headley, Thomas Jeffrey; Plass, Richard Anton
2004-12-01
Thermal actuators have proven to be a robust actuation method in surface-micromachined MEMS processes. Their higher output force and lower input voltage make them an attractive alternative to more traditional electrostatic actuation methods. A predictive model of thermal actuator behavior has been developed and validated that can be used as a design tool to customize the performance of an actuator to a specific application. This tool has also been used to better understand thermal actuator reliability by comparing the maximum actuator temperature to the measured lifetime. Modeling thermal actuator behavior requires the use of two sequentially coupled models, the first to predict the temperature increase of the actuator due to the applied current and the second to model the mechanical response of the structure due to the increase in temperature. These two models have been developed using Matlab for the thermal response and ANSYS for the structural response. Both models have been shown to agree well with experimental data. In a parallel effort, the reliability and failure mechanisms of thermal actuators have been studied. Their response to electrical overstress and electrostatic discharge has been measured and a study has been performed to determine actuator lifetime at various temperatures and operating conditions. The results from this study have been used to determine a maximum reliable operating temperature that, when used in conjunction with the predictive model, enables us to design in reliability and customize the performance of an actuator at the design stage.
Verification of Beam Models for Ionic Polymer-Metal Composite Actuator
Ai-hong Ji; Hoon Cheol Park; Quoc Viet Nguyen; Jang Woo Lee; Young Tai Yoo
2009-01-01
Ionic Polymer-Metal Composite (IPMC) can work as an actuator by applying a few voltages. A thick IPMC actuator, where Nation-117 membrane was synthesized with polypyrrole/alumina composite tiller, was analyzed to verify the equivalent beam and equivalent bimorph beam models. The blocking force and tip displacement of the IPMC actuator were measured with a DC power supply and Young's modulus of the IPMC strip was measured by bending and tensile tests respectively. The calculated maximum tip displacement and the Young's modulus by the equivalent beam model were almost identical to the corresponding measured data. Finite element analysis with thermal analogy technique was utilized in the equivalent bimorph beam model to numerically reproduce the force-displacement relationship of the IPMC actuator. The results by the equivalent bimorph beam model agreed well with the force-displacement relationship acquired by the measured data. It is confirmed that the equivalent beam and equivalent bimorph beam models are practically and effectively suitable for predicting the tip displacement, blocking force and Young's modulus of IPMC actuators with different thickness and different composite of ionic polymer membrane.
Inverse grey-box model-based control of a dielectric elastomer actuator
Jones, Richard William; Sarban, Rahimullah
2012-01-01
An accurate physical-based electromechanical model of a commercially available tubular dielectric elastomer (DE) actuator has been developed and validated. In this contribution, the use of the physical-based electromechanical model to formulate a model-based controller is examined. The choice of...
A mathematical model for smart functionally graded beam integrated with shape memory alloy actuators
Sepiani, H.; Ebrahimi, F. [University of Tehran, Tehran (Iran, Islamic Republic of); Karimipour, H. [Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)
2009-12-15
This paper presents a theoretical study of the thermally driven behavior of a shape memory alloy (SMA)/FGM actuator under arbitrary loading and boundary conditions by developing an integrated mathematical model. The model studied is established on the geometric parameters of the three-dimensional laminated composite box beam as an actuator that consists of a functionally graded core integrated with SMA actuator layers with a uniform rectangular cross section. The constitutive equation and linear phase transformation kinetics relations of SMA layers based on Tanaka and Nagaki model are coupled with the governing equation of the actuator to predict the stress history and to model the thermo-mechanical behavior of the smart shape memory alloy/FGM beam. Based on the classical laminated beam theory, the explicit solution to the structural response of the structure, including axial and lateral deflections of the structure, is investigated. As an example, a cantilever box beam subjected to a transverse concentrated load is solved numerically. It is found that the changes in the actuator's responses during the phase transformation due to the strain recovery are significant
A mathematical model for smart functionally graded beam integrated with shape memory alloy actuators
This paper presents a theoretical study of the thermally driven behavior of a shape memory alloy (SMA)/FGM actuator under arbitrary loading and boundary conditions by developing an integrated mathematical model. The model studied is established on the geometric parameters of the three-dimensional laminated composite box beam as an actuator that consists of a functionally graded core integrated with SMA actuator layers with a uniform rectangular cross section. The constitutive equation and linear phase transformation kinetics relations of SMA layers based on Tanaka and Nagaki model are coupled with the governing equation of the actuator to predict the stress history and to model the thermo-mechanical behavior of the smart shape memory alloy/FGM beam. Based on the classical laminated beam theory, the explicit solution to the structural response of the structure, including axial and lateral deflections of the structure, is investigated. As an example, a cantilever box beam subjected to a transverse concentrated load is solved numerically. It is found that the changes in the actuator's responses during the phase transformation due to the strain recovery are significant
We present the modeling, fabrication and measurement results of a novel electrostatic actuator with a coplanar pre-charged electrode. Different from the conventional electrostatic actuator, the pull-in voltage of the proposed actuator can be freely controlled even after fabrication by inducing charges prior to use in the auxiliary electrode right next to the actuation electrode. To investigate the static and dynamic characteristics of the proposed actuator, analytical models were first developed on the basis of a parallel-plate capacitor model. We then successfully designed, fabricated, and evaluated a micro-switch with a fixed–fixed beam and a coplanar pre-charged electrode. By properly introducing a dimple structure, the pull-in voltage of the fabricated micro-switch was reduced from 71.2 V to 6.8 V when pre-charged by 58.8 V. The resonant frequency of the fabricated micro-switch was 84.8% of the initial resonant frequency when the reduced pull-in voltage of the device was half of the original pull-in voltage. These measurement results were compared with those from the analytical models and FEM simulation, showing deviations of less than 12%. This work can favorably be adapted and used in designing an electrostatic micro-switch since the proposed switch can remarkably reduce the pull-in voltage as desired without notable performance degradation
Study of a pseudo-empirical model approach to characterize plasma actuators
The use of plasma actuators is a recent technology that imposes a localized electric force that is used to control air flows. A suitable representation of actuation enables to undertake plasma actuators optimization, to design flow-control strategies, or to analyse the flow stabilization that can be attained by plasma forcing. The problem description may be clearly separated in two regions. An outer region, where the fluid is electrically neutral, in which the flow is described by the Navier-Stokes equation without any forcing term. An inner region, that forms a thin boundary layer, where the fluid is ionized and electric forces are predominant. The outer limit of the inner solution becomes the boundary condition for the outer problem. The outer problem can then be solved with a slip velocity that is issued from the inner solution. Although the solution for the inner problem is quite complex it can be contoured proposing pseudo-empirical models where the slip velocity of the outer problem is determined indirectly from experiments. This pseudo-empirical model approach has been recently tested in different cylinder flows and revealed quite adapted to describe actuated flow behaviour. In this work we determine experimentally the influence of the duty cycle on the slip velocity distribution. The velocity was measured by means of a pitot tube and flow visualizations of the starting vortex (i.e. the induced flow when actuation is activated in a quiescent air) have been done by means of the Schlieren technique. We also performed numerical experiments to simulate the outer region problem when actuation is activated in a quiescent air using a slip velocity distribution as a boundary condition. The experimental and numerical results are in good agreement showing the potential of this pseudo-empirical model approach to characterize the plasma actuation.
Single actuator wave-like robot (SAW): design, modeling, and experiments.
Zarrouk, David; Mann, Moshe; Degani, Nir; Yehuda, Tal; Jarbi, Nissan; Hess, Amotz
2016-01-01
In this paper, we present a single actuator wave-like robot, a novel bioinspired robot which can move forward or backward by producing a continuously advancing wave. The robot has a unique minimalistic mechanical design and produces an advancing sine wave, with a large amplitude, using only a single motor but with no internal straight spine. Over horizontal surfaces, the robot does not slide relative to the surface and its direction of locomotion is determined by the direction of rotation of the motor. We developed a kinematic model of the robot that accounts for the two-dimensional mechanics of motion and yields the speed of the links relative to the motor. Based on the optimization of the kinematic model, and accounting for the mechanical constraints, we have designed and built multiple versions of the robot with different sizes and experimentally tested them (see movie). The experimental results were within a few percentages of the expectations. The larger version attained a top speed of 57 cm s(-1) over a horizontal surface and is capable of climbing vertically when placed between two walls. By optimizing the parameters, we succeeded in making the robot travel by 13% faster than its own wave speed. PMID:27367548
Two stainless steel templates were fabricated using electric-spark machining, and a hierarchical surface texture of ionic polymer was produced using both polishing and replication methods, which produced microscale and nanoscale groove-shaped microstructures at the surface of the polymer. The surface morphology of the Nafion membrane and metal electrode were observed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). SEM and EDS line-scan analysis indicated that the interfacial surface area was considerably increased and an excellent metal electrode was obtained with the production of a hierarchical surface texture. The displacement, blocking force, and electric current were measured using home-built apparatus. The results revealed that the combined polishing and replication method significantly improved the electromechanical performance of the ionic polymer–metal composite (IPMC). Compared with sandblasted Nafion-based IPMC, the blocking force, displacement, and electric current of the replicated Nafion-based IPMC were 4.39, 2.35, and 1.87 times higher, respectively. The IPMC fabricated in this work exhibited a competitive blocking force compared with recently reported actuators. (paper)
Development of a dc Motor Model and an Actuator Efficiency Model
Watkins, John Clifford; Mc Kellar, Michael George; DeWall, Kevin George
2001-07-01
For the past several years, researchers at the Idaho National Engineering and Environmental Laboratory, under the sponsorship of the U.S. Nuclear Regulatory Commission, have been investigating the ability of motor-operated valves (MOVs) used in Nuclear Power Plants to close or open when subjected to design basis flow and pressure loads. Part of this research addresses the response of a dcpowered motor-operated gate valve to assess whether it will achieve flow isolation and to evaluate whether it will slow down excessively under design-basis conditions and thus fail to achieve the required stroke time. As part of this research, we have developed a model of a dc motor operating under load and a model of actuator efficiency under load based on a first principle evaluation of the equipment. These models include the effect that reduced voltage at the Motor Control Center and elevated containment temperatures have on the performance of a dc powered MOV. The model also accounts for motor torque and speed changes that result from the heatup of the motor during the stroke. These models are part of the Motor- Operated Valve In Site Test Assessment (MISTA) software which is capable of independently evaluating the ability of dc-powered motoroperated gate valves to achieve flow isolation and to meet required stroke times under design-basis conditions. This paper presents an overview of the dc motor model and the actuator efficiency under load model. The paper then compares the analytical results from the models with the results of actual dc motor and actuator testing, including comparisons of the effect reduced voltage, elevated containment temperature, and motor heating during the stroke have on an MOV.
Murali Muniraj; Ramaswamy Arulmozhiyal
2015-01-01
A control actuation system has been used extensively in automotive, aerospace, and defense applications. The major challenges in modeling control actuation system are rise time, maximum peak to peak overshoot, and response to nonlinear system with percentage error. This paper addresses the challenges in modeling and real time implementation of control actuation system for missiles glider applications. As an alternative fuzzy-PID controller is proposed in BLDC motor drive followed by linkage m...
Model of Polysilicon Electro-thermal Micro Actuator and Research of Micro Scale Effect
ZHANGYong-yu; SHENXue-jin; CHENXiao-yang
2004-01-01
A type of crank beam electro-thermal mircro actuator was prescribed Mechanical model of the actuatar was estabilished,and the static characteristic was analzed Comparing the theoretical analzsis with experimental data,it is found that the thermodynamic character of material in micro actuator has a different variable regularity contrasted to that used in macro scale machines.it is the micro scale effect that results in the deriation between the simulating result and experimental results the thermodynamic expression of polysilicon which was fitted by means of the experimental data concerned was used to modify the mechanical model The modifiex model ,in which the mircro scale thermodynamic characteristic characteristic was considered,was more reasonable and could make the optimal design and control strategies analyzing the straight-line micro actuator more feasible.
Continuum damage model for ferroelectric materials and its application to multilayer actuators
Gellmann, Roman; Ricoeur, Andreas
2016-05-01
In this paper a micromechanical continuum damage model for ferroelectric materials is presented. As a constitutive law it is implemented into a finite element (FE) code. The model is based on micromechanical considerations of domain switching and its interaction with microcrack growth and coalescence. A FE analysis of a multilayer actuator is performed, showing the initiation of damage zones at the electrode tips during the poling process. Further, the influence of mechanical pre-stressing on damage evolution and actuating properties is investigated. The results provided in this work give useful information on the damage of advanced piezoelectric devices and their optimization.
Fault Tolerance for Industrial Actuators in Absence of Accurate Models and Hardware Redundancy
Papageorgiou, Dimitrios; Blanke, Mogens; Niemann, Hans Henrik;
2015-01-01
This paper investigates Fault-Tolerant Control for closed-loop systems where only coarse models are available and there is lack of actuator and sensor redundancies. The problem is approached in the form of a typical servomotor in closed-loop. A linear model is extracted from input/output data...
So, Hongyun
2013-10-31
© 2013, Springer-Verlag Berlin Heidelberg. This paper reports on a novel thermal actuator with sub-micron metallic structures and a buckling arm to operate with low voltages and to generate very large deflections, respectively. A lumped electrothermal model and analysis were also developed to validate the mechanical design and easily predict the temperature distribution along arms of the sub-micron actuator. The actuator was fabricated via the combination of electron beam lithography to form actuator arms with a minimum feature size of 200 nm and lift-off process to deposit a high aspect ratio nickel structure. Reproducible displacements of up to 1.9 μm at the tip were observed up to 250 mV under confocal microscope. The experimentally measured deflection values and theoretically calculated temperature distribution by the developed model were compared with finite element analysis results and they were in good agreement. This study shows a promising approach to develop more sophisticated nano actuators required larger deflections for manipulation of sub-micron scale objects with low-power consumption.
Couple Control Model Implementation on Antagonistic Mono- and Bi-Articular Actuators
Prattico, Flavio; Yamamoto, Shin-ichiroh
2014-01-01
Recently, robot assisted therapy devices are increasingly used for spinal cord injury (SCI) rehabilitation in assisting handicapped patients to regain their impaired movements. Assistive robotic systems may not be able to cure or fully compensate impairments, but it should be able to assist certain impaired functions and ease movements. In this study, a couple control model for lower-limb orthosis of a body weight support gait training system is proposed. The developed leg orthosis implements the use of pneumatic artificial muscle as an actuation system. The pneumatic muscle was arranged antagonistically to form two pair of mono-articular muscles (i.e., hip and knee joints), and a pair of bi-articular actuators (i.e., rectus femoris and hamstring). The results of the proposed couple control model showed that, it was able to simultaneously control the antagonistic mono- and bi-articular actuators and sufficiently performed walking motion of the leg orthosis.
Choi, Jun-Ho; Ahn, Jaeho; Kim, Jin-Bong; Kim, Young-Cheol; Lee, Jung-Yong; Oh, Il-Kwon
2016-04-01
An active, frequency selective surface utilizing a silver-nanowire-coated dielectric elastomer with a butterfly-shaped aperture pattern is realized by properly exploiting the electroactive control of two antagonistic functions (stretching vs compression) on a patterned dielectric elastomer actuator. PMID:26864249
Modelling of piezoelectric actuator dynamics for active structural control
Hagood, Nesbitt W.; Chung, Walter H.; Von Flotow, Andreas
1990-01-01
The paper models the effects of dynamic coupling between a structure and an electrical network through the piezoelectric effect. The coupled equations of motion of an arbitrary elastic structure with piezoelectric elements and passive electronics are derived. State space models are developed for three important cases: direct voltage driven electrodes, direct charge driven electrodes, and an indirect drive case where the piezoelectric electrodes are connected to an arbitrary electrical circuit with embedded voltage and current sources. The equations are applied to the case of a cantilevered beam with surface mounted piezoceramics and indirect voltage and current drive. The theoretical derivations are validated experimentally on an actively controlled cantilevered beam test article with indirect voltage drive.
Toward the Design of Multi Asymmetric Surface Dielectric Barrier Discharge (ASDBD) Actuators
This paper investigates the electrical behaviors of a single-ASDBD actuator and a two- ASDBD one supplied in sinusoidal mode (1-10 kHz). The main objective of our research is to determine the optimum frequency values for functioning of these actuators with a given power supply. For that purpose, we determine the electrical power density transmitted to the actuators versus frequency through two methods: i) a theoretical method, based on an impedance calculation, and ii) an experimental method, based on direct electrical measurements. These methods show that the addition of a second ASDBD changes the resonance frequency value of the actuator by moving it towards the low frequencies
Minami Takato; Masaki Tatani; Hirozumi Oku; Yuki Okane; Junichi Tanida; Shinpei Yamasaki; Ken Saito; Fumio Uchikoba
2014-01-01
Micro-robotic systems are increasingly used in medicine and other fields requiring precision engineering. This paper proposes a piezoelectric impact- type rotary actuator and applies it to a millimetre-size robot controlled by a hardware neuron model. The rotary actuator and robot are fabricated by micro-electro- mechanical systems (MEMS) technology. The actuator is composed of multilayer piezoelectric elements. The rotational motion of the rotor is generated by the impact head attached to th...
Modelling and Fuzzy Control of an Efficient Swimming Ionic Polymer-metal Composite Actuated Robot
Qi Shen
2013-10-01
Full Text Available In this study, analytical techniques and fuzzy logic methods are applied to the dynamic modelling and efficient swimming control of a biomimetic robotic fish, which is actuated by an ionic polymer-metal composite (IPMC. A physical-based model for the biomimetic robotic fish is proposed. The model incorporates both the hydrodynamics of the IPMC tail and the actuation dynamics of the IPMC. The comparison of the results of the simulations and experiments shows the feasibility of the dynamic model. By using this model, we found that the harmonic control of the actuation frequency and voltage amplitude of the IPMC is a principal mechanism through which the robotic fish can obtain high thrust efficiency while swimming. The fuzzy control method, which is based on the knowledge of the IPMC fish’s dynamic behaviour, successfully utilized this principal mechanism. By comparing the thrust performance of the robotic fish with other control methods via simulation, we established that the fuzzy controller was able to achieve faster acceleration compared with what could be achieved with a conventional PID controller. The thrust efficiency during a steady state was superior to that with conventional control methods. We also found that when using the fuzzy control method the robotic fish can always swim near a higher actuation frequency, which could obtain both the desired speed and high thrust efficiency.
Port-based modeling and optimal control for a new very versatile energy efficient actuator
Gerelli, Oscar; Carloni, Raffaella; STRAMIGIOLI, Stefano
2009-01-01
In this paper, we analyze in depth the innovative very versatile and energy efficient (V2E2) actuator proposed in Stramigioli et al. (2008). The V2E2 actuator is intended to be used in all kind of robotics and powered prosthetic applications in which energy consumption is a critical issue. In particular, this work focuses on the development of a port-based Hamiltonian model of the V2E2 and presents an optimal control architecture which exploits the intrinsic hybrid characteristics of the actu...
Toward the Design of Multi Asymmetric Surface Dielectric Barrier Discharge (ASDBD) Actuators
This paper investigates the electrical and mechanical behaviors of a single-ASDBD actuator and a two-ASDBD one supplied in sinusoidal mode (1–10 kHz). The main objective of our research is to determine the optimum frequency values for the function of these actuators with a given power supply. For this purpose, we determine the electrical power density input to the actuators versus frequency through two methods: i) a semi-theoretical method, based on an impedance calculation, and ii) an experimental method, based on direct electrical measurements. These methods show that the addition of a second ASDBD changes the resonance frequency value of the actuator by moving it towards low frequencies. After characterizing the aerodynamic mobile layer structure induced by the single-ASDBD actuator, we analyze experimentally the mechanical response of a two-ASDBD actuator as a function of the inter-ASDBD distance. The experiments demonstrate that the induced electric wind velocity and the electro-mechanical yield of a two-ASDBD actuator reach a maximum value for an optimum inter-ASDBD distance, which is a useful value for the design of highly efficient multi-ASDBD actuators. (plasma technology)
Reversionary rotation of actuated particles for microfluidic near-surface mixing
Derks, R.J.S.; Frijns, A.J.H.; Prins, M.W.J.; Dietzel, A.H.
2011-01-01
The off-axis motion of particles actuated by axial magnetic or gravitational forces is studied in fluidic channels. Single actuated superparamagnetic micro-particles starting from channel walls travel towards the channel center and show unforeseen reversionary rotation phenomena. Different stages of
A validated model for induction heating of shape memory alloy actuators
Saunders, Robert N.; Boyd, James G.; Hartl, Darren J.; Brown, Jonathan K.; Calkins, Frederick T.; Lagoudas, Dimitris C.
2016-04-01
Shape memory alloy (SMA) actuators deliver high forces while being compact and reliable, making them ideal for consideration in aerospace applications. One disadvantage of these thermally driven actuators is their slow cyclic time response compared to conventional actuators. Induction heating has recently been proposed to quickly heat SMA components. However efforts to date have been purely empirical. The present work approachs this problem in a computational manner by developing a finite element model of induction heating in which the time-harmonic electromagnetic equations are solved for the Joule heat power field, the energy equation is solved for the temperature field, and the linear momentum equations are solved to find the stress, displacement, and internal state variable fields. The combined model was implemented in Abaqus using a Python script approach and applied to SMA torque tube and beam actuators. The model has also been used to examine magnetic flux concentrators to improve the induction systems performance. Induction heating experiments were performed using the SMA torque tube, and the model agreed well with the experiments.
Design, modelling and control of a micro-positioning actuator based on magnetic shape memory alloys
Minorowicz, Bartosz; Leonetti, Giuseppe; Stefanski, Frederik; Binetti, Giulio; Naso, David
2016-07-01
This paper presents an actuator based on magnetic shape memory alloys (MSMAs) suitable for precise positioning in a wide range (up to 1 mm). The actuator is based on the spring returned operating mode and uses a Smalley wave spring to maintain the same operating parameters of a classical coil spring, while being characterized by a smaller dimension. The MSMA element inside the actuator provides a deformation when excited by an external magnetic field, but its behavior is characterized by an asymmetric and saturated hysteresis. Thus, two models are exploited in this work to represent such a non-linear behavior, i.e., the modified and generalized Prandtl–Ishlinskii models. These models are particularly suitable for control purposes due to the existence of their analytical inversion that can be easily exploited in real time control systems. To this aim, this paper investigates three closed-loop control strategies, namely a classical PID regulator, a PID regulator with direct hysteresis compensation, and a combined PID and feedforward compensation strategy. The effectiveness of both modelling and control strategies applied to the designed MSMA-based actuator is illustrated by means of experimental results.
Near-surface gravity actuated pipe (GAP{sup TM}) system for Brazilian deepwater fluid transfer
Fromage, Lionel; Brown, Paul A. [SBM Offshore (Monaco)
2009-12-19
The recent discovery of new deep water and ultra-deep water oil and gas fields offshore Brazil, including pre-salt reservoirs, has become a focal point for field development Operators and Contractors. The aggressive nature of fluids (sour, high density) in combination with deeper waters implies potential flow assurance issues. These issues challenge riser and pipeline technology to find cost effective solutions for hydrocarbon fluid transfer in field development scenarios involving phased tied-back. The near-surface GAP{sup TM}, system (Gravity Actuated Pipe{sup TM}), which has been in operation for more than two years on the Kikeh field offshore Malaysia in 1325 m of water between a Dry Tree Unit (SPAR) and a turret-moored FPSO, is considered to meet these challenges since such a product is quasi independent of water depth and takes advantage of being near surface to optimize flow assurance. Furthermore the GAP{sup TM} has undergone technical upgrades when compared to the Kikeh project in order to make it suitable for the more hostile met ocean conditions offshore Brazil. This paper presents the design features, the construction and assembly plans in Brazil and the offshore installation of a GAP fluid transfer system for operation in Brazilian deep waters. (author)
An Asymmetric Hysteresis Model and Parameter Identification Method for Piezoelectric Actuator
Haichen Qin
2014-01-01
Full Text Available Hysteresis behaviour degrades the positioning accuracy of PZT actuator for ultrahigh-precision positioning applications. In this paper, a corrected hysteresis model based on Bouc-Wen model for modelling the asymmetric hysteresis behaviour of PZT actuator is established by introducing an input bias φ and an asymmetric factor ΔΦ into the standard Bouc-Wen hysteresis model. A modified particle swarm optimization (MPSO algorithm is established and realized to identify and optimize the model parameters. Feasibility and effectiveness of MPSO are proved by experiment and numerical simulation. The research results show that the corrected hysteresis model can represent the asymmetric hysteresis behaviour of the PZT actuator more accurately than the noncorrected hysteresis model based on the Bouc-Wen model. The MPSO parameter identification method can effectively identify the parameters of the corrected and noncorrected hysteresis models. Some cases demonstrate the corrected hysteresis model and the MPSO parameter identification method can be used to model smart materials and structure systems with the asymmetric hysteresis behaviour.
Yan, Su
2007-12-01
To improve the fuel consumption of a satellite, maintain the position and orientation and eliminate the unwanted thruster vibration, intelligent composite structure technology was proposed in the ADPICAS (Adaptive Damping and Positioning using Intelligent Composite Active Structures) project funded by the ONR (Office of Naval Research) in collaboration with the NRL (Naval Research Laboratory) in 2000. This dissertation introduces the author's research achievements in developing smart composite panels for the ADPICAS project, including modeling, actuator optimization, and vibration control. The method of separation of variables is presented to derive the analytical shape functions for complex composite structures with asymmetric constraints, i.e., the 2-D Adaptive Composite Circular Plate (ACCP) in cylindrical coordinates and the 3-D Adaptive Composite Satellite Dish (ACSD) in spherical coordinates. Following these solutions, two modeling approaches are developed to obtain the models of adaptive composite panels including an adaptive composite beam, the ACCP, and the ACSD. One model approach is to employ the Lagrange-Rayleigh-Ritz method based on the developed analytical shape functions. Meanwhile, the transfer function estimation technique, combining the finite element analyses, is applied to obtain the numerical model of the composite panels. Aiming at improving the actuation efficiency, a Genetic Algorithm is presented to optimize the piezoelectric actuator placement on the composite panels. Taking the inertia and stiffness characteristics of the piezoelectric actuators into account, this algorithm defines the performance index as a weighted summation of control error and control energy consumption, and obtained the optimal solution that minimizes the performance index. Furthermore, an adaptive disturbance observer/feed-forward (ADOB/FF) controller is proposed to achieve simultaneous precision positioning and vibration suppression of the adaptive composite panels
A Strategy Tackling Local Minimum of Direct Search Method in Modeling a Hydraulic Actuator
刘云山; 陈晓辉
2013-01-01
A strategy for attacking the local minimum problem of direct search method is developed for modeling a hydraulic actuator. The Nelder-Mead direct search method is combined with Ordinary Least Squares which can used to optimize the parameters which the model function is in linear with. The model fitting results show that this strategy can reach a solution more close to the global minimum than the Nelder-Mead direct search method used alone.
Hodgins, M.; Rizzello, G.; Naso, D.; York, A.; Seelecke, S.
2014-10-01
Dielectric electro-active polymer (DEAP) technology holds promise for enabling lightweight, energy efficient, and scalable actuators. The circular DEAP actuator configuration (also known as cone or diaphragm actuator) in particular shows potential in applications such as pumps, valves, micro-positioners and loudspeakers. For a quantitative prediction of the actuator behavior as well as for design optimization tasks, material models which can reproduce the coupled electromechanical behavior inherent to these actuators are necessary. This paper presents a non-linear viscoelastic model based on an electro-mechanical Ogden free energy expression for the DEAP. The DEAP model is coupled with a spring/mass system to study the dynamic performance of such a representative system from static behavior to 50 Hz. The system is identified and validated by several different experiments.
Dielectric electro-active polymer (DEAP) technology holds promise for enabling lightweight, energy efficient, and scalable actuators. The circular DEAP actuator configuration (also known as cone or diaphragm actuator) in particular shows potential in applications such as pumps, valves, micro-positioners and loudspeakers. For a quantitative prediction of the actuator behavior as well as for design optimization tasks, material models which can reproduce the coupled electromechanical behavior inherent to these actuators are necessary. This paper presents a non-linear viscoelastic model based on an electro-mechanical Ogden free energy expression for the DEAP. The DEAP model is coupled with a spring/mass system to study the dynamic performance of such a representative system from static behavior to 50 Hz. The system is identified and validated by several different experiments. (paper)
Pseudo-Rigid-Body Model and Kinematic Analysis of MRI-Actuated Catheters
Greigarn, Tipakorn; Çavuşoğlu, M. Cenk
2015-01-01
This paper presents a kinematic study of a pseudorigid-body model (PRBM) of MRI-compatible, magnetically actuated, steerable catheters. It includes a derivation of a mathematical model of the PRBM of the catheter, singularity studies of the model, and a new manipulability measure. While the forward kinematics of the model presented here is applicable to PRBMs for other applications, actuation method is unique to the particular design. Hence, a careful study of singularities and manipulability of the model is required. The singularities are studied from the underlying equations of motion with intuitive interpretations. The proposed manipulability measure is a generalization of the inverse condition number manipulability measure of robotic manipulators. While the PRBM is an approximation of the flexible catheter, kinematic studies of the PRBM still provide some insight into feasibility and limitations of the catheter, which is beneficial to the design and motion planning of the catheter. PMID:26413380
Nonlinear dynamic modeling for smart material electro-hydraulic actuator development
Larson, John P.; Dapino, Marcelo J.
2013-03-01
Smart material electro-hydraulic actuators use hydraulic rectification by one-way check valves to amplify the motion of smart materials, such as magnetostrictives and piezoelectrics, in order to create compact, lightweight actuators. A piston pump driven by a smart material is combined with a hydraulic cylinder to form a self-contained, power-by-wire actuator that can be used in place of a conventional hydraulic system without the need for hydraulic lines and a centralized pump. The performance of an experimental actuator driven by a 12.7 mm diameter, 114 mm length Terfenol-D rod is evaluated over a range of applied input frequencies, loads, and currents. The peak performance achieved is 37 W, moving a 220 N load at a rate of 17 cm/s and producing a blocked pressure of 12.5 MPa. Additional tests are conducted to quantify the dynamic behavior of the one-way reed valves using a scanning laser vibrometer to identify the frequency response of the reeds and the effect of the valve seat and fluid mass loading. A lumped-parameter model is developed for the system that includes valve inertia and fluid response nonlinearities, and the model results are compared with the experimental data.
Hunt, A.; Chen, Z.; Tan, X.; Kruusmaa, M.
2016-03-01
Ionic electroactive polymers (IEAPs), particularly ionic polymer-metal composites (IPMCs) and carbon-polymer composites (CPCs), bend when a voltage is applied on their electrodes, and conversely, they generate an electrical signal when subjected to a mechanical bending. In this work we study and compare the capabilities of IPMC and CPC actuators and sensors in closed-loop control applications. We propose and realize an integrated IEAP sensor-actuator design, characterize its performance using three different materials, and compare the results. The design consists of two short IEAP actuators and one sensor mechanically coupled together in a parallel configuration, and an attached rigid extension significantly longer than the IEAPs. This allows the device to be compliant, simple to construct, lightweight, easy to miniaturize, and functionally similar to a one-degree-of-freedom rotational joint. For control design and accurate position sensing in feedback experiments, we adapt physics-based and control-oriented models of actuation and sensing dynamics, and perform experiments to identify their parameters. In performance characterization, both model-based {H}∞ control and proportional-integral control are explored. System responses to step inputs, sinusoids, and random references are measured, and long-duration sinusoidal tracking experiments are performed. The results show that, while IEAP position sensing is stable for only a limited time-span, H ∞ control significantly improves the performance of the device.
Distributed and lumped element models for a bimorph-actuated micromirror
A procedure to model electrothermally actuated devices is developed and demonstrated using a 1D scanning micromirror. The micromirror is actuated by thermal bimorphs and an embedded platinum (Pt) resistor is used for generating Joule heating. Electrothermal, thermal and thermomechanical models are developed and integrated to generate a compact electrothermomechanical model. The electrothermal model relates the thermal power generated in the device to the applied voltage. The thermomechanical model evaluates the mirror rotation angle. The thermal model is developed by drawing analogy between heat flow in the device and current flow through an electrical transmission line. It provides the temperature of the embedded heater and the bimorph actuators. The heat loss coefficient to the surrounding atmosphere is obtained from finite element (FE) simulations. The distributed thermal resistances are represented by an equivalent circuit model with a few elements. A simplification of the circuit model is proposed when small length scales are involved. Rotation angle per unit power input predicted by the circuit model has an error of less than 8% compared to experimental results.
Plasma actuators for bluff body flow control
Kozlov, Alexey V.
The aerodynamic plasma actuators have shown to be efficient flow control devices in various applications. In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. This work is motivated by the need to reduce landing gear noise for commercial transport aircraft via an effective streamlining created by the actuators. The experiments are performed at Re D = 20,000...164,000. Circular cylinders in cross-flow are chosen for study since they represent a generic flow geometry that is similar in all essential aspects to a landing gear oleo or strut. The minimization of the unsteady flow separation from the models and associated large-scale wake vorticity by using actuators reduces the radiated aerodynamic noise. Using either steady or unsteady actuation at ReD = 25,000, Karman shedding is totally eliminated, turbulence levels in the wake decrease significantly and near-field sound pressure levels are reduced by 13.3 dB. Unsteady actuation at an excitation frequency of St D = 1 is found to be most effective. The unsteady actuation also has the advantage that total suppression of shedding is achieved for a duty cycle of only 25%. However, since unsteady actuation is associated with an unsteady body force and produces a tone at the actuation frequency, steady actuation is more suitable for noise control applications. Two actuation strategies are used at ReD = 82,000: spanwise and streamwise oriented actuators. Near field microphone measurements in an anechoic wind tunnel and detailed study of the near wake using LDA are presented in the study. Both spanwise and streamwise actuators give nearly the same noise reduction level of 11.2 dB and 14.2 dB, respectively, and similar changes in the wake velocity profiles. The contribution of the actuator induced noise is found to be small compared to the natural shedding
Suzuki, Y.
2016-05-01
This article demonstrates the practical applicability of a method of modelling shape memory alloys (SMAs) as actuators. For this study, a pair of SMA wires was installed in an antagonistic manner to form an actuator, and a linear differential equation that describes the behaviour of the actuator’s generated force relative to its input voltage was derived for the limited range below the austenite onset temperature. In this range, hysteresis need not be considered, and the proposed SMA actuator can therefore be practically applied in linear control systems, which is significant because large deformations accompanied by hysteresis do not necessarily occur in most vibration control cases. When specific values of the parameters used in the differential equation were identified experimentally, it became clear that one of the parameters was dependent on ambient airflow velocity. The values of this dependent parameter were obtained using an additional SMA wire as a sensor. In these experiments, while the airflow distribution around the SMA wires was varied by changing the rotational speed of the fans in the wind tunnels, an input voltage was conveyed to the SMA actuator circuit, and the generated force was measured. In this way, the parameter dependent on airflow velocity was estimated in real time, and it was validated that the calculated force was consistent with the measured one.
A study on modelling of a butterfly-type control valve by a pneumatic actuator
This paper studies on the modelling of a butterfly-type control valve actuating by an on-off pneumatic solenoid valve. The mathematical model is composed of nonlinear differential equations three parts: (i) a solenoid valve, (ii) a pneumatic cylinder, (iii) a rotary-type butterfly valve. The flow characteristics of the butterfly control valve is analysed by a computer simulator, then its simple transfer function is identified from the step responses.
Kholwadwala, Deepesh K.; Johnston, Gabriel A.; Rohrer, Brandon R.; Galambos, Paul C.; Okandan, Murat
2007-07-24
The present invention comprises a novel, lightweight, massively parallel device comprising microelectromechanical (MEMS) fluidic actuators, to reconfigure the profile, of a surface. Each microfluidic actuator comprises an independent bladder that can act as both a sensor and an actuator. A MEMS sensor, and a MEMS valve within each microfluidic actuator, operate cooperatively to monitor the fluid within each bladder, and regulate the flow of the fluid entering and exiting each bladder. When adjacently spaced in a array, microfluidic actuators can create arbitrary surface profiles in response to a change in the operating environment of the surface. In an embodiment of the invention, the profile of an airfoil is controlled by independent extension and contraction of a plurality of actuators, that operate to displace a compliant cover.
Approaches for Reduced Order Modeling of Electrically Actuated von Karman Microplates
Saghir, Shahid
2016-07-25
This article presents and compares different approaches to develop reduced order models for the nonlinear von Karman rectangular microplates actuated by nonlinear electrostatic forces. The reduced-order models aim to investigate the static and dynamic behavior of the plate under small and large actuation forces. A fully clamped microplate is considered. Different types of basis functions are used in conjunction with the Galerkin method to discretize the governing equations. First we investigate the convergence with the number of modes retained in the model. Then for validation purpose, a comparison of the static results is made with the results calculated by a nonlinear finite element model. The linear eigenvalue problem for the plate under the electrostatic force is solved for a wide range of voltages up to pull-in. Results among the various reduced-order modes are compared and are also validated by comparing to results of the finite-element model. Further, the reduced order models are employed to capture the forced dynamic response of the microplate under small and large vibration amplitudes. Comparison of the different approaches are made for this case. Keywords: electrically actuated microplates, static analysis, dynamics of microplates, diaphragm vibration, large amplitude vibrations, nonlinear dynamics
Modeling of a micro-cantilevered piezo-actuator considering the buffer layer and electrodes
Considering the buffer layer and electrodes, we set up a piezoelectric multilayered cantilever model to evaluate the dynamic performance of the micro-cantilevered piezo-actuator (MCPA) based on Euler–Bernoulli beam theory without considering the residual stresses on the MCPA. Adopting the material and geometric parameters of the previous MCPAs with the different lengths, the first-mode resonance frequency–beam length, the tip deflection–voltage and harmonic response curves are simulated by using the traditional and proposed models, and the results based on the proposed model are much closer to the experimental and finite element simulation results than those based on the traditional model, indicating that the proposed model is valid for evaluating the actuation performances of the MCPA. The effect of the mechanical damping and bending stiffness on the actuation performance of the MCPA is also discussed. Using the proposed model, the dependences of the first-mode resonance frequency and tip deflection of the MCPA on non-piezoelectric layer thicknesses are analyzed at the certain driving voltage. The above-mentioned methods and conclusions can be used for the structure optimized design and performance improvement of MCPAs. (paper)
Thomas Sinn
2015-07-01
Full Text Available The use of morphing components on aerospace structures can greatly increase the versatility of an aircraft. This paper presents the design, manufacturing and testing of a new kind of adaptive airfoil with actuation through Shape Memory Alloys (SMA. The developed adaptive flap system makes use of a novel actuator that employs SMA wires in an antagonistic arrangement with a Post-Buckled Precompressed (PBP mechanism. SMA actuators are usually used in an antagonistic arrangement or are arranged to move structural components with linearly varying resistance levels similar to springs. Unfortunately, most of this strain energy is spent doing work on the passive structure rather than performing the task at hand, like moving a flight control surface or resisting air loads. A solution is the use of Post-Buckled Precompressed (PBP actuators that are arranged so that the active elements do not waste energy fighting passive structural stiffnesses. One major problem with PBP actuators is that the low tensile strength of the piezoelectric elements can often result in tensile failure of the actuator on the convex face. A solution to this problem is the use of SMA as actuator material due to their tolerance of tensile stresses. The power consumption to hold deflections is reduced by approximately 20% with the Post-Buckled Precompressed mechanism. Conventional SMAs are essentially non-starters for many classes of aircraft due to the requirement of holding the flight control surfaces in a given position for extremely long times to trim the vehicle. For the reason that PBP actuators balance out air and structural loads, the steady-state load on the SMAs is essentially negligible, when properly designed. Simulations and experiments showed that the SMAPBP actuator shows tip rotations on the order of 45°, which is nearly triple the levels achieved by piezoelectric PBP actuators. The developed SMAPBP actuator was integrated in a NACA0012 airfoil with a flexible skin
Demerdash, N. A.; Nehl, T. W.
1979-01-01
A comprehensive digital model for the analysis of the dynamic-instantaneous performance of a power conditioner fed samarium-cobalt permanent magnet brushless DC motor is presented. The particular power conditioner-machine system at hand, for which this model was developed, is a component of an actual prototype electromechanical actuator built for NASA-JSC as a possible alternative to hydraulic actuators as part of feasibility studies for the shuttle orbiter applications. Excellent correlation between digital simulated and experimentally obtained performance data was achieved for this specific prototype. This is reported on in this paper. Details of one component of the model, its applications and the corresponding results are given in this paper.
A dynamic model for generating actuator specifications for small arms barrel active stabilization
Pathak, Anupam; Brei, Diann; Luntz, Jonathan; Lavigna, Chris
2006-03-01
Due to stresses encountered in combat, it is known that soldier marksmanship noticeably decreases regardless of prior training. Active stabilization systems in small arms have potential to address this problem to increase soldier survivability and mission effectiveness. The key to success is proper actuator design, but this is highly dependent on proper specification which is challenging due to the human/weapon interaction. This paper presents a generic analytical dynamic model which is capable of defining the necessary actuation specifications for a wide range of small arms platforms. The model is unique because it captures the human interface--shoulder and arm--that introduces the jitter disturbance in addition to the geometry, inertial properties and active stabilization stiffness of the small arms platform. Because no data to date is available for actual shooter-induced disturbance in field conditions, a method is given using the model to back-solve from measured shooting range variability data the disturbance amplitude information relative to the input source (arm or shoulder). As examples of the applicability of the model to various small arms systems, two different weapon systems were investigated: the M24 sniper weapon and the M16 assault rifle. In both cases, model based simulations provided valuable insight into impact on the actuation specifications (force, displacement, phase, frequency) due to the interplay of the human-weapon-active stabilization interface including the effect of shooter-disturbance frequency, disturbance location (shoulder vs. arm), and system parameters (stiffness, barrel rotation).
Wu, Yongxian
Ionic polymer-metal composites (IPMCs) are soft bending actuators and sensors. A typical IPMC consists of a thin perfluorinated ionomer membrane, noble metal electrodes plated on both faces, and is neutralized with the necessary amount of cations. They respond to electric stimulus by generating large bending motions and produce electric signals upon sudden bending deformations. These actuation and sensing responses, which result from the coupled chemo-electro-mechanical interactions at the nano-scale level, depend on the structure of the ionomer, the morphology of the metal electrodes, the nature of the cations, and the degree of the hydration. IPMCs have been considered for potential applications in artificial muscles, robotic systems, medical devices, and other biomimetic applications. A series of systematic experimental characterizations are performed on both Nafion- and Flemion-based IPMCs in various cation forms. Compared with Nafion-based IPMCs, Flemion-based IPMCs with fine dendritic gold electrodes have higher ion-exchange capacity, better surface conductivity, higher hydration capacity, and higher longitudinal stiffness. Flemion-based IPMCs show a greater bending deformation towards the anode without back relaxation under a DC voltage. This displacement towards the anode is linearly related to the charge accumulation at the cathode. In contrast, Nafion-based IPMCs in alkali-metal cations initially have a fast bending towards the anode, followed by a slow relaxation in the opposite direction as charges continue to move towards the cathode boundary layer. Based on the understanding of the factors that affect IPMCs' performance, novel methods to tailor the IPMCs' electro-mechanical responses are developed. By modifying the associated cations, i.e., introducing various single cations (including alkali-metal, alkyl-ammonium, or multivalent metal cations) and cation combinations, diverse actuation behaviors can be obtained and optimized. The actuation motions of
Genetic Algorithm Approaches for Actuator Placement
Crossley, William A.
2000-01-01
This research investigated genetic algorithm approaches for smart actuator placement to provide aircraft maneuverability without requiring hinged flaps or other control surfaces. The effort supported goals of the Multidisciplinary Design Optimization focus efforts in NASA's Aircraft au program. This work helped to properly identify various aspects of the genetic algorithm operators and parameters that allow for placement of discrete control actuators/effectors. An improved problem definition, including better definition of the objective function and constraints, resulted from this research effort. The work conducted for this research used a geometrically simple wing model; however, an increasing number of potential actuator placement locations were incorporated to illustrate the ability of the GA to determine promising actuator placement arrangements. This effort's major result is a useful genetic algorithm-based approach to assist in the discrete actuator/effector placement problem.
Treviso, Felipe; Silveira, Marilia A.; Flores Filho, Aly F.; Dorrell, David G.
2016-01-01
This paper presents a study on an induction planar actuator concept. The device uses the same principles as a linear induction motor in which the interaction between a travelling magnetic field and a conducting surface produces eddy currents that leads to the generation of a thrust force and can result in movement over a metallic surface. This can benefit the inspection of metallic surfaces based on the driving platform provided by the induction planar actuator. Equations of the magnetic and electric fields are presented and, by means of these equations, the forces involved were calculated. The behaviour of thrust and normal forces was analysed through the equations and by numerical models, and compared with the results obtained by measurements on a device prototype built in the laboratory as part of the study. With relation to the surface under inspection that forms the secondary, three cases were analysed: (1) a double-layered secondary formed by aluminium and ferromagnetic slabs; (2) a single aluminium layer and (3) a single ferromagnetic layer. Theoretical and measured values of thrust and normal forces showed good correlation. PMID:27007377
Theoretical modelling and experimental results of electromechanical actuation of an elastomer
Electromechanical actuation is a growing field of research today both for applications or theoretical modelling. The interaction between electric and mechanical constraints has been used for electromechanic actuators or generators based on elastomers. From a theoretical point of view, many recent works have been focused on uniaxial or biaxial stretching of elastomer plates with compliant electrodes. Free stretching or pre-strained samples have been theoretically modelled, mainly by neo-Hookean equations. In this work, we present theoretical and experimental results of electromechanic actuation of an elastomer (the widely used 3M VHB4910, an acrylic foam) in a pre-strained case and a free case. Experimental characterization of the material shows that the Ogden model gives the best accurate fitting of mechanical properties. Thus, a theoretical development based on this model is carried out in order to obtain the curves describing the electromechanical behaviour of the material. The mechanical instability related to wrinkling of the material is theoretically calculated and experimentally verified. (paper)
Modeling and optimal vibration control of conical shell with piezoelectric actuators
Wang Weiyuan; Wei Yingjie; Wang Cong; Zou Zhenzhu
2008-01-01
In this paper numerical simulations of active vibration control for conical shell structure with distributed piezoelectric actuators is presented. The dynamic equations of conical shell structure are derived using the finite element model (FEM) based on Mindlin's plate theory. The results of modal calculations with FEM model are accurate enough for engineering applications in comparison with experiment results. The Electromechanical influence of distributed piezoelectric actuators is treated as a boundary condition for estimating the control force. The independent modal space control (IMSC) method is adopted and the optimal linear quadratic state feedback control is implemented so that the best control performance with the least control cost can be achieved. Optimal control effects are compared with controlled responses with other non-optimal control parameters. Numerical simulation results are given to demonstrate the effectiveness of the control scheme.
Wind Turbine Large-Eddy Simulations on Very Coarse Grid Resolutions using an Actuator Line Model
Tossas, Luis A Martínez; Meneveau, Charles
2016-01-01
In this work the accuracy of the Actuator Line Model (ALM) in Large Eddy Simulations of wind turbine flow is studied under the specific conditions of very coarse spatial resolutions. For finely-resolved conditions, it is known that ALM provides better accuracy compared to the standard Actuator Disk Model (ADM) without rotation. However, we show here that on very coarse resolutions, flow induction occurring at rotor scales can affect the predicted inflow angle and can adversely affect the ALM predictions. We first provide an illustration of coarse LES to reproduce wind tunnel measurements. The resulting flow predictions are good, but the challenges in predicting power outputs from the detailed ALM motivate more detailed analysis on a case with uniform inflow. We present a theoretical framework to compare the filtered quantities that enter the Large-Eddy Simulation equations as body forces with a scaling relation between the filtered and unfiltered quantities. The study aims to apply the theoretical derivation ...
In this paper computational fluid dynamics (CFD) simulations are performed using ANSYS CFX to compare wake interaction results obtained from two rotor modelling methodologies: the standard actuator disc and the blade element momentum model (BEM). The unsteady simulations embed Coriolis forces and neutral stability conditions in the surface layer and stable conditions in the free stream. The BEM method is implemented in the CFD code through a pre-processing set of files that employs look-up tables. The control system for the wind turbines is considered through look-up tables that are constructed based on operational wind farm data. Simulations using the actuator disc and BEM methodologies have been performed using a number of different turbulence models in order to compare the wind turbine wake structure results. The use of URANS and LES numerical methods, coupled with the two different methodologies of representing the turbine, enables an assessment to be made of the details required for varying degrees of accuracy in computing the wake structures. The findings stress the importance of including the rotation of the wake and the non-uniform load on the rotor in LES simulations to account for more accurate turbulence intensity levels in the near wake
Lavaroni, Luca; Watson, Simon J.; Cook, Malcolm J.; Dubal, Mark R.
2014-06-01
In this paper computational fluid dynamics (CFD) simulations are performed using ANSYS CFX to compare wake interaction results obtained from two rotor modelling methodologies: the standard actuator disc and the blade element momentum model (BEM). The unsteady simulations embed Coriolis forces and neutral stability conditions in the surface layer and stable conditions in the free stream. The BEM method is implemented in the CFD code through a pre-processing set of files that employs look-up tables. The control system for the wind turbines is considered through look-up tables that are constructed based on operational wind farm data. Simulations using the actuator disc and BEM methodologies have been performed using a number of different turbulence models in order to compare the wind turbine wake structure results. The use of URANS and LES numerical methods, coupled with the two different methodologies of representing the turbine, enables an assessment to be made of the details required for varying degrees of accuracy in computing the wake structures. The findings stress the importance of including the rotation of the wake and the non-uniform load on the rotor in LES simulations to account for more accurate turbulence intensity levels in the near wake.
Actuator disk modeling of the Mexico rotor with OpenFOAM⋆
Jeromin A.; Bentamy A.; Schaffarczyk A.P.
2014-01-01
The implementation of an actuator disk with prescribed constant load for OpenFOAM was first presented by Svenning. In our presentation it was enhanced to compute local loads from local velocities by given aerodynamic lift and drag coefficients. The new model was then verified using the so called MEXICO rotor. Extensive comparisons to the experiments and other simulations were performed. The results for the thrust force was comparable to BEm and measurement wereas torque for the separated case...
Complete modelling of a piezo actuator last-generation injector for diesel injection systems
Salvador Rubio, Francisco Javier; PLAZAS TORRES, ALEJANDRO HERNÁN; Gimeno García, Jaime; Carreres Talens, Marcos
2014-01-01
An experimental and computational study of an increasingly used third-generation common-rail injection system with a piezo actuator has been carried out. A complete characterization of the different elements of the system, both geometrically and hydraulically, has been performed in order to describe its behaviour. The information obtained through the characterization has been used to create a one-dimensional model that has been implemented in the commercial software AMESim and ext...
A top-down multi-scale modeling for actuation response of polymeric artificial muscles
Yang, Qianxi; Li, Guoqiang
2016-07-01
A class of innovative artificial muscles made of high-strength polymeric fibers such as fishing lines or sewing threads have been discovered recently. These muscles are fabricated by a simple "twist-insertion" procedure, which have attracted increasing attention due to their low cost and readily availability, giant tensile stroke, record energy density, and easy controllability. In the present paper, we established a multi-scale modeling framework for the thermomechanical actuation responses by a top-down strategy, spanning from macro-scale helical spring analysis down to molecular level chain interaction study. Comparison between modeling results and experimental results exhibited excellent agreement. The effect of the micro-, meso- and macro-scale parameters on the actuation responses of the artificial muscle was further discussed through a parametric study per the validated model. This work helps understand the physical origin behind the remarkable tensile actuation behavior of the twisted-then-coiled polymeric artificial muscles and also provides inspirations for optimal design of advanced artificial muscles made by twist-insertion procedure.
An electromechanical model for sensing and actuation of ionic polymer metal composites
Ionic polymer metal composites (IPMCs) are active materials that exhibit a bidirectional electromechanical coupling. An IPMC is an electrolytic polymer membrane that is plated by two metallic electrodes. A voltage difference across the electrodes generates structural deformations; and, conversely, a mechanical deformation yields a voltage difference across the electrodes. In this paper, we develop a physics-based model for the sensing and actuation of IPMCs undergoing small deformations. The model describes a variety of phenomena taking place in an IPMC, including counterions, solvent, and polymer motions; electric dipole generation; osmotic effects; boundary layer formation; polymer swelling; and local charge imbalances. We specialize the model to the analysis of linear static deformations of a thin and flat IPMC, for which we derive a plate-like model. The reduced-order linear plate-like model is derived by using the principle of virtual work and a parallel-plate approximation for the electrostatic field inside the IPMC. The proposed plate-like model is equivalent to traditional plate models for moderately thin piezoelectric bimorph plates. The constitutive parameters of the plate-like model are expressed in terms of fundamental IPMC physical quantities, such as polymer hydration level, IPMC dielectric constant, polymer and electrode dimensions and elastic properties, and solute concentration. We validate the reduced-order model by comparing its predictions with available experimental data on mechanical stiffness, electric capacitance, and sensing and actuation capacity of water-hydrated Nafion in Na+ form. The model predictions are in close agreement with experimental findings. The model provides new insights into the design and optimization of IPMCs and into the role of the IPMC electric capacitance on electromechanical performance. More specifically, we show that the IPMC capacitance is largely independent of the IPMC thickness and highly correlated to the
An analytical model for electrode-ceramic interaction in multilayer piezoelectric actuators
B. L. Wang; J. C. Han
2007-01-01
The present paper develops an analytical model for multi-electrodes in multi-layered piezoelectric actuators, in which the electrodes are vertical to and terminated at the edges of the medium and electroelastic field concentrations ahead of the electrodes in the multilayer piezoelectric actuators are examined. By considering a representative unit in realistic multilayers, the problem is formulated in terms of electric potential between the electrode tips and results in a system of singular integral equations in which the electric potential is taken as unknown function. Effects are investigated of electrode spacing and piezoelectric coupling on the singular electroelastic fields at the electrode tips, and closed-form expressions are given for the electromechanical field near the electrode tips. Exact solution for un-coupled dielectrics is provided, where no piezoelectric coupling is present.
Keivani, Maryam; Mardaneh, Mohamadreza; Koochi, Ali; Rezaei, Morteza; Abadyan, Mohamadreza
2016-02-01
Herein, the dynamic pull-in instability of cantilever nanoactuator fabricated from conductive cylindrical nanowire with circular cross-section is studied under the presence of Casimir force. The Gurtin-Murdoch surface elasticity in combination with the couple stress theory is employed to incorporate the coupled effects of surface energy and size phenomenon. Using Green-Lagrange strain, the higher order surface stress components are incorporated in the governing equation. The Dirichlet mode is considered and an asymptotic solution, based on the path integral approach, is applied to consider the effect of the Casimir attraction. Furthermore, the influence of structural damping is considered in the model. The nonlinear governing equation is solved using analytical reduced order method (ROM). The effects of various parameters on the dynamic pull-in parameters, phase planes and stability threshold of the actuator are demonstrated.
Patre, Parag; Joshi, Suresh M.
2011-01-01
Decentralized adaptive control is considered for systems consisting of multiple interconnected subsystems. It is assumed that each subsystem s parameters are uncertain and the interconnection parameters are not known. In addition, mismatch can exist between each subsystem and its reference model. A strictly decentralized adaptive control scheme is developed, wherein each subsystem has access only to its own state but has the knowledge of all reference model states. The mismatch is estimated online for each subsystem and the mismatch estimates are used to adaptively modify the corresponding reference models. The adaptive control scheme is extended to the case with actuator failures in addition to mismatch.
Walton, John P.; Coutu, Ronald A.; Starman, LaVern
2015-02-01
There are numerous applications for micromirror arrays seen in our everyday lives. From flat screen televisions and computer monitors, found in nearly every home and office, to advanced military weapon systems and space vehicles, each application bringing with it a unique set of requirements. The microelectromechanical systems (MEMS) industry has researched many ways micromirror actuation can be accomplished and the different constraints on performance each design brings with it. This paper investigates a new "zipper" approach to electrostatically driven micromirrors with the intent of improving duel plane beam steering by coupling large deflection angles, over 30°, and a fast switching speed. To accomplish this, an extreme initial deflection is needed which can be reached using high stress bimorph beams. Currently this requires long beams and high voltage for the electrostatic pull in or slower electrothermal switching. The idea for this "zipper" approach is to stack multiple beams of a much shorter length and allow for the deflection of each beam to be added together in order to reach the required initial deflection height. This design requires much less pull-in voltage because the pull-in of one short beam will in turn reduce the height of the all subsequent beams, making it much easier to actuate. Using modeling and simulation software to characterize operations characteristics, different bimorph cantilever beam configurations are explored in order to optimize the design. These simulations show that this new "zipper" approach increases initial deflection as additional beams are added to the assembly without increasing the actuation voltage.
Zhu, Zicai; Wang, Yanjie; Liu, Yanfa; Asaka, Kinji; Sun, Xiaofei; Chang, Longfei; Lu, Pin
2016-07-01
Water containing ionic polymer-metal composites (IPMCs) show complex deformation properties with water content. In order to develop a simple application-oriented model for engineering application, actuation mechanisms and model equations should be simplified as necessary. Beginning from our previous comprehensive multi-physical model of IPMC actuator, numerical analysis was performed to obtain the main factors influencing the bending deformation and the corresponding simplified model. In this paper, three aspects are mainly concerned. (1) Regarding mass transport process, the diffusion caused by concentration gradient mainly influences the concentrations of cation and water at the two electrode boundaries. (2) By specifying the transport components as hydrated cation and free water in the model, at the cathode, the hydrated cation concentration profile is more flat, whereas the concentrations of both free water and the total water show drastic changes. In general, the two influence the redistribution of cation and water but have little impact on deformation prediction. Thus, they can be ignored in the simplification. (3) An extended osmotic pressure is proposed to cover all eigen stresses simply with an effective osmotic coefficient. Combining with a few other linearized methods, a simplified model has been obtained by sacrificing the prediction precision on the transport process. Furthermore, the improved model has been verified by fitting with IPMC deformation evolved with water content. It shows that the simplified model has the ability to predict the complex deformations of IPMCs.
Cotroneo, Vincenzo; Davis, William N.; Reid, Paul B.; Schwartz, Daniel A.; Trolier-McKinstry, Susan; Wilke, Rudeger H. T.
2011-09-01
The present generation of X-ray telescopes emphasizes either high image quality (e.g. Chandra with sub-arc second resolution) or large effective area (e.g. XMM-Newton), while future observatories under consideration (e.g. Athena, AXSIO) aim to greatly enhance the effective area, while maintaining moderate (~10 arc-seconds) image quality. To go beyond the limits of present and planned missions, the use of thin adjustable optics for the control of low-order figure error is needed to obtain the high image quality of precisely figured mirrors along with the large effective area of thin mirrors. The adjustable mirror prototypes under study at Smithsonian Astrophysical Observatory are based on two different principles and designs: 1) thin film lead-zirconate-titanate (PZT) piezoelectric actuators directly deposited on the mirror back surface, with the strain direction parallel to the glass surface (for sub-arc-second angular resolution and large effective area), and 2) conventional leadmagnesium- niobate (PMN) electrostrictive actuators with their strain direction perpendicular to the mirror surface (for 3-5 arc second resolution and moderate effective area). We have built and operated flat test mirrors of these adjustable optics. We present the comparison between theoretical influence functions as obtained by finite element analysis and the measured influence functions obtained from the two test configurations.
Electromagnetic (EM) solenoid actuators are widely used in many applications such as the automobile, aerospace, printing and food industries where repetitive, often high-speed linear or rotating motions are required. In some of these applications they are used as highspeed 'switching' valves for switching pneumatic channels. This paper describes the finite element (FE) modelling and design of high-speed solenoid actuators. Operating at frequencies between 150-300 Hz, these actuators are unique in terms of the large force they produce (8-15 N) and the requirement for very long lifetime (2-5 billion cycles). The complex nature of electromagnetic, motional and thermal problems is discussed. The methodologies for FE modelling of such high-performance actuators are developed and discussed. These are used for modelling, design, performance evaluation and prediction of the above high-speed actuators. Modelling results showing some of the key design features of the actuators are presented in terms of force produced as a function of various design parameters
Muniraj, Murali; Arulmozhiyal, Ramaswamy
2015-01-01
A control actuation system has been used extensively in automotive, aerospace, and defense applications. The major challenges in modeling control actuation system are rise time, maximum peak to peak overshoot, and response to nonlinear system with percentage error. This paper addresses the challenges in modeling and real time implementation of control actuation system for missiles glider applications. As an alternative fuzzy-PID controller is proposed in BLDC motor drive followed by linkage mechanism to actuate fins in missiles and gliders. The proposed system will realize better rise time and less overshoot while operating in extreme nonlinear dynamic system conditions. A mathematical model of BLDC motor is derived in state space form. The complete control actuation system is modeled in MATLAB/Simulink environment and verified by performing simulation studies. A real time prototype of the control actuation is developed with dSPACE-1104 hardware controller and a detailed analysis is carried out to confirm the viability of the proposed system. PMID:26613102
Rossini, L.; Chetelat, O.; Onillon, E.; Perriard, Y.
2013-01-01
This paper presents an analytical model for the force and torque developed by a reaction sphere actuator for satellite attitude control. The reaction sphere is an innovative momentum exchange device consisting of a magnetic bearings spherical rotor that can be electronically accelerated in any direction making all the three axes of stabilized spacecrafts controllable by a unique device. The spherical actuator is composed of an 8-pole permanent magnet spherical rotor and of a 20-coil stator. F...
Active knits are a unique architectural approach to meeting emerging smart structure needs for distributed high strain actuation with simultaneous force generation. This paper presents an analytical state-based model for predicting the actuation response of a shape memory alloy (SMA) garter knit textile. Garter knits generate significant contraction against moderate to large loads when heated, due to the continuous interlocked network of loops of SMA wire. For this knit architecture, the states of operation are defined on the basis of the thermal and mechanical loading of the textile, the resulting phase change of the SMA, and the load path followed to that state. Transitions between these operational states induce either stick or slip frictional forces depending upon the state and path, which affect the actuation response. A load–extension model of the textile is derived for each operational state using elastica theory and Euler–Bernoulli beam bending for the large deformations within a loop of wire based on the stress–strain behavior of the SMA material. This provides kinematic and kinetic relations which scale to form analytical transcendental expressions for the net actuation motion against an external load. This model was validated experimentally for an SMA garter knit textile over a range of applied forces with good correlation for both the load–extension behavior in each state as well as the net motion produced during the actuation cycle (250% recoverable strain and over 50% actuation). The two-dimensional analytical model of the garter stitch active knit provides the ability to predict the kinetic actuation performance, providing the basis for the design and synthesis of large stroke, large force distributed actuators that employ this novel architecture. (paper)
Reduced-order modeling of high-speed jets controlled by arc filament plasma actuators
Sinha, Aniruddha; Serrani, Andrea; Samimy, Mo
2013-02-01
Arc filament plasma actuators applied to high-speed and high Reynolds number jets have demonstrated significant mixing enhancement when operated near the jet column mode (JCM) frequency. A feedback-oriented reduced-order model is developed for this flow from experimental data. The existent toolkit of stochastic estimation, proper orthogonal decomposition, and Galerkin projection is adapted to yield a 35-dimensional model for the unforced jet. Explicit inclusion of a "shift mode" stabilizes the model. The short-term predictive capability of instantaneous flow fields is found to degrade beyond a single flow time step, but this horizon may be adequate for feedback control. Statistical results from long-term simulations agree well with experimental observations. The model of the unforced jet is augmented to incorporate the effects of plasma actuation. Periodic forcing is modeled as a deterministic pressure wave specified on the inflow boundary of the modeling domain. Simulations of the forced model capture the nonlinear response that leads to optimal mixing enhancement in a small range of frequencies near the JCM.
Torsional fatigue model for limitorque type SMB/SB/SBD actuators for motor-operated valves
Kalsi Engineering, Inc. has recently developed a computer program to predict the torsional fatigue life of Limitorque Type SMB/SB/SBD actuators for motor-operated valves under given loading levels, including those that exceed the ratings. The development effort was an outgrowth of the open-quote Thrust Rating Increase close-quote test program. The fatigue model computes all pertinent stress components and their variations as a function of the loading ramp. The cumulative damage and fatigue life due to stress cycling is computed by use of a modification of Miner's rule. Model predictions were validated against actual cyclic loading test results
Analysis of VAWT aerodynamics and design using the Actuator Cylinder flow model
Aagaard Madsen, Helge; Schmidt Paulsen, Uwe; Vita, Luca
2012-01-01
The actuator cylinder (AC) flow model is defined as the ideal VAWT rotor. Radial directed volume forces are applied on the circular path of the VAWT rotor airfoil and constitute an energy conversion in the flow. The power coefficient for the ideal as well as the real energy conversion is defined. The describing equations for the two-dimensional AC model are presented and a solution method splitting the final solution in a linear and non-linear part is briefly described. A family of loadforms ...
Torsional fatigue model for limitorque type SMB/SB/SBD actuators for motor-operated valves
Somogyi, D.; Alvarez, P.D.; Kalsi, M.S. [Kalsi Engineering, Inc., Sugar Land, TX (United States)
1996-12-01
Kalsi Engineering, Inc. has recently developed a computer program to predict the torsional fatigue life of Limitorque Type SMB/SB/SBD actuators for motor-operated valves under given loading levels, including those that exceed the ratings. The development effort was an outgrowth of the {open_quote}Thrust Rating Increase{close_quote} test program. The fatigue model computes all pertinent stress components and their variations as a function of the loading ramp. The cumulative damage and fatigue life due to stress cycling is computed by use of a modification of Miner`s rule. Model predictions were validated against actual cyclic loading test results.
Tracking control of piezoelectric actuators using a polynomial-based hysteresis model
Gan, Jinqiang; Zhang, Xianmin; Wu, Heng
2016-06-01
A polynomial-based hysteresis model that describes hysteresis behavior in piezoelectric actuators is presented. The polynomial-based model is validated by comparing with the classic Prandtl-Ishlinskii model. Taking the advantages of the proposed model into consideration, inverse control using the polynomial-based model is proposed. To achieve better tracking performance, a hybrid control combining the developed inverse control and a proportional-integral-differential feedback loop is then proposed. To demonstrate the effectiveness of the proposed tracking controls, several comparative experiments of the polynomial-based model and Prandtl-Ishlinskii model are conducted. The experimental results show that inverse control and hybrid control using the polynomial-based model in trajectory-tracking applications are effective and meaningful.
Modeling, fabrication and testing of MEMS tunable inductors varied with piezoelectric actuators
Modeling, fabrication and measurements of tunable inductors are presented where inductance tuning is achieved through mechanical displacement, by piezoelectric actuation, of mutually-coupled coils. The modified Greenhouse method is utilized as a modeling tool to predict the inductance variations as a function of both translation and angular displacement, where coils and traces which are arbitrarily oriented with respect to one another are considered. The use of this modeling approach is verified through experimental results where electrical measurements of inductances are compared with the modeled inductances. The inductance model compares well with the measurements and within 10% of the measured inductance with a 3% mean error. In addition, the impact of the interconnect widths on tunable inductor performances is assessed for both negatively and positively coupled tunable inductor cases, where devices with interconnect widths ranging between 10 and 40 µm are considered. Tuning ratios as high as ∼3.9:1 were measured for the negatively-coupled coil designs with 18 V actuation; this corresponds to minimum and maximum quality factors of 5.72 (at 4.05 GHz with a 2.80 nH inductance) and 14.91 (at 2.25 GHz with 10.86 nH inductance), respectively. For the positively coupled inductors, tuning ratios of ∼1.2:1 resulted with inductance and peak quality factors of 7.70 nH and ∼18 (3.69 GHz), respectively. With 18 V actuation, these values tune to 6.57 nH with a Q ∼18 (4.46 GHz). Residual poling stress was found to limit the practical tuning ratio to ∼1.8:1 for the negatively coupled coils. (paper)
Integrated modeling for determining launch survival and limitations of actuated lightweight mirrors
Cohan, Lucy E.; Miller, David W.
2008-07-01
The future of space telescopes lies in large, lightweight, segmented aperture systems. Segmented apertures eliminate manufacturability and launch vehicle fairing diameter as apertures size constraints. Low areal density, actuated segments allow the systems to meet both launch mass restrictions and on-orbit wavefront error requirements. These systems, with silicon carbide as a leading material, have great potential for increasing the productivity, affordability, and manufacturability of future space-based optical systems. Thus far, progress has been made on the manufacturing, sensing, actuation, and on-orbit control of such systems. However, relatively little attention has been paid to the harsh environment of launch. The launch environment may dominate aspects of the design of the mirror segments, with survivability requirements eliminating many potentially good designs. Integrated modeling of a mirror segment can help identify trends in mirror geometries that maximize launch performance, ensuring survivability without drastically over designing the mirror. A finite element model of a single, ribbed, actuated, silicon carbide mirror segment is created, and is used to develop a dynamic, state-space model, with launch load spectra as disturbance inputs, and mirror stresses as performance outputs. The parametric nature of this model allows analysis of many geometrically different mirror segments, helping to identify key parameters for launch survival. The modeling method described herein will enable identification of the design decisions that are dominated by launch, and will allow for development of launch-load alleviation techniques to further push the areal density boundaries in support of the creation of larger and lighter mirrors than previously possible.
Modeling, Validation, and Control of Electronically Actuated Pitman Arm Steering for Armored Vehicle
Vimal Rau Aparow
2016-01-01
Full Text Available In this study, 2 DOF mathematical models of Pitman arm steering system are derived using Newton’s law of motion and modeled in MATLAB/SIMULINK software. The developed steering model is included with a DC motor model which is directly attached to the steering column. The Pitman arm steering model is then validated with actual Pitman arm steering test rig using various lateral inputs such as double lane change, step steer, and slalom test. Meanwhile, a position tracking control method has been used in order to evaluate the effectiveness of the validated model to be implemented in active safety system of a heavy vehicle. The similar method has been used to test the actual Pitman arm steering mechanism using hardware-in-the-loop simulation (HILS technique. Additional friction compensation is added in the HILS technique in order to minimize the frictional effects that occur in the mechanical configuration of the DC motor and Pitman arm steering. The performance of the electronically actuated Pitman arm steering system can be used to develop a firing-on-the-move actuator (FOMA for an armored vehicle. The FOMA can be used as an active safety system to reject unwanted yaw motion due to the firing force.
Modeling and control of actuators for high performance structural dynamic testing
Most research in the structural engineering field uses either a simplified data-based model or a physics-based model to describe the dynamic behavior of servo-hydraulic actuators. In either way, the nominal model is typically used for modeling, analysis and control design. However, little effort has been directed to model uncertainties that are inherently associated with any physical system. A robust modeling approach is proposed in this study that can characterize both parametric and non-parametric uncertainties. The combination of this uncertainty with the nominal model provides a powerful tool to analyze the system performance and stability properties. Several control techniques are evaluated experimentally, and an H∞ robust control design is demonstrated to achieve the best performance as well as good robustness. (paper)
Carbon nanotubes can be assembled into macroscopic thin film materials called buckypapers. To incorporate buckypaper actuators into engineering systems, it is of high importance to understand their material property-actuation performance relationships in order to model and predict the behavior of these actuators. The electromechanical actuation of macroscopic buckypaper structures and their actuators, including single and multi-walled carbon nanotube buckypapers and aligned single-walled nanotube buckypapers, were analyzed and compared. From the experimental evidence, this Letter discusses the effects of the fundamental material properties, including Young modulus and electrical double layer properties, on actuation performance of the resultant actuators. -- Highlights: ► In this study we identified the figure of merit of the electromechanical conversion. ► Different type of buckypaper was realized and characterized for actuation properties. ► The results demonstrated the potential of Buckypapers/Nafion for actuation
Lee, Gil-Yong; Choi, Jung-Oh; Kim, Myeungseon; Ahn, Sung-Hoon
2011-10-01
Ionic polymer-metal composites (IPMCs) are one of the most popular types of electro-active polymer actuator, due to their low electric driving potential, large deformation range, and light weight. IPMCs have been used as actuators or sensors in many areas of biomedical and robotic engineering. In this research, IPMCs were studied as a biaxial bending actuator capable of smart and flexible motion. We designed and fabricated this bending actuator and implemented it to have a reliable actuating motion using a systematic approach. The resulting device was bar shaped with a square cross section and had four insulated electrodes on its surface. By applying different voltages to these four electrodes, a biaxial bending motion can be induced. To construct this actuator, several fabrication processes were considered. We modified the Nafion stacking method, and established a complete sequence of actuator fabrication processes. Using these processes, we were able to fabricate an IPMC biaxial bending actuator with both high actuating force and high flexibility. Several experiments were conducted to investigate and verify the performance of the actuator. The IPMC actuator system was modeled from experimentally measured data, and using this actuator model, a closed-loop proportional integral (PI) controller was designed. Reference position tracking performances of open-loop and closed-loop systems were compared. Finally, circular motion tracking performances of the actuator tip were tested under different rotation frequencies and radii of a reference trajectory circle.
Ionic polymer–metal composites (IPMCs) are one of the most popular types of electro-active polymer actuator, due to their low electric driving potential, large deformation range, and light weight. IPMCs have been used as actuators or sensors in many areas of biomedical and robotic engineering. In this research, IPMCs were studied as a biaxial bending actuator capable of smart and flexible motion. We designed and fabricated this bending actuator and implemented it to have a reliable actuating motion using a systematic approach. The resulting device was bar shaped with a square cross section and had four insulated electrodes on its surface. By applying different voltages to these four electrodes, a biaxial bending motion can be induced. To construct this actuator, several fabrication processes were considered. We modified the Nafion stacking method, and established a complete sequence of actuator fabrication processes. Using these processes, we were able to fabricate an IPMC biaxial bending actuator with both high actuating force and high flexibility. Several experiments were conducted to investigate and verify the performance of the actuator. The IPMC actuator system was modeled from experimentally measured data, and using this actuator model, a closed-loop proportional integral (PI) controller was designed. Reference position tracking performances of open-loop and closed-loop systems were compared. Finally, circular motion tracking performances of the actuator tip were tested under different rotation frequencies and radii of a reference trajectory circle
Yan, Huijie; Yang, Liang; Qi, Xiaohua; Ren, Chunsheng
2015-02-01
The effect of a DC bias on the electrohydrodynamics (EHD) force induced by a surface dielectric barrier AC discharge actuator for airflow control at the atmospheric pressure is investigated. The measurement of the surface potential due to charge deposition at different DC biases is carried out by using a special designed corona like discharge potential probe. From the surface potential data, the plasma electromotive force is shown not affected much by the DC biases except for some reduction of the DC bias near the exposed electrode edge for the sheath-like configuration. The total thrust is measured by an analytical balance, and an almost linear relationship to the potential voltage at the exposed electrode edge is found for the direct thrust force. The temporally averaged ionic wind characteristics are investigated by Pitot tube sensor and schlieren visualization system. It is found that the ionic wind velocity profiles with different DC biases are almost the same in the AC discharge plasma area but gradually diversified in the further downstream area as well as the upper space away from the discharge plasma area. Also, the DC bias can significantly modify the topology of the ionic wind produced by the AC discharge actuator. These results can provide an insight into how the DC biases to affect the force generation.
A mixture theory framework for modeling the mechanical actuation of ionic polymer metal composites
An ionic polymer metal composite (IPMC) is a porous charged polymer saturated with an electrolytic solvent and plated by two metallic electrodes. A voltage difference across the electrodes generates structural deformations; similarly, a mechanical deformation yields a voltage difference across the electrodes. The electrolytic solvent comprises a mobile ionic species and an uncharged solvent. Interactions between mobile ions and the solvent and between the solvent and the backbone polymer are responsible for sensing and actuation. We present a mixture theory framework for mechanical modeling of IPMCs and of species interactions occurring therein. The model consists of three coupled linear partial differential equations, and it is applicable to a large variety of IPMC geometries and microstructures. The framework allows for a thorough description of actuation mechanisms, including osmotic pressure, hydraulic pressure, and electrostatic forces. The model describes the presence of boundary layers of mobile ions and solvent concentrations in the vicinity of the electrodes. We particularize the general three-dimensional model to a slender IPMC, and we derive a one-dimensional distributed model using the Euler–Bernoulli beam theory and a parallel-plate approximation. We validate our theoretical findings through a set of experiments conducted on Nafion-based IPMCs
Stroke maximizing and high efficient hysteresis hybrid modeling for a rhombic piezoelectric actuator
Shao, Shubao; Xu, Minglong; Zhang, Shuwen; Xie, Shilin
2016-06-01
Rhombic piezoelectric actuator (RPA), which employs a rhombic mechanism to amplify the small stroke of PZT stack, has been widely used in many micro-positioning machineries due to its remarkable properties such as high displacement resolution and compact structure. In order to achieve large actuation range along with high accuracy, the stroke maximizing and compensation for the hysteresis are two concerns in the use of RPA. However, existing maximization methods based on theoretical model can hardly accurately predict the maximum stroke of RPA because of approximation errors that are caused by the simplifications that must be made in the analysis. Moreover, despite the high hysteresis modeling accuracy of Preisach model, its modeling procedure is trivial and time-consuming since a large set of experimental data is required to determine the model parameters. In our research, to improve the accuracy of theoretical model of RPA, the approximation theory is employed in which the approximation errors can be compensated by two dimensionless coefficients. To simplify the hysteresis modeling procedure, a hybrid modeling method is proposed in which the parameters of Preisach model can be identified from only a small set of experimental data by using the combination of discrete Preisach model (DPM) with particle swarm optimization (PSO) algorithm. The proposed novel hybrid modeling method can not only model the hysteresis with considerable accuracy but also significantly simplified the modeling procedure. Finally, the inversion of hysteresis is introduced to compensate for the hysteresis non-linearity of RPA, and consequently a pseudo-linear system can be obtained.
National Aeronautics and Space Administration — Being relatively new to the field, electromechanical actuators in aerospace applications lack the knowledge base compared to ones accumulated for the other actuator...
Actuator disk modeling of the Mexico rotor with OpenFOAM⋆
Jeromin A.
2014-01-01
Full Text Available The implementation of an actuator disk with prescribed constant load for OpenFOAM was first presented by Svenning. In our presentation it was enhanced to compute local loads from local velocities by given aerodynamic lift and drag coefficients. The new model was then verified using the so called MEXICO rotor. Extensive comparisons to the experiments and other simulations were performed. The results for the thrust force was comparable to BEm and measurement wereas torque for the separated case (25 m/s inflow velocity gave rather wide-spreading results.
Real-time hybrid model testing of floating wind turbines: sensitivity to limited actuation
Bachynski, Erin Elizabeth; Chabaud, Valentin Bruno; Sauder, Thomas Michel
2015-01-01
Real-time hybrid model testing (ReaTHM) is a new approach for conducting small-scale experimental campaign [1], [2] and [3]. In the case of a floating wind turbine in a wave basin, the aerodynamic loads on the wind turbine may be applied based on simultaneous simulations (coupled to the experiments), while the wave loads and floater response are physically tested. The objective of this paper is to demonstrate the effects of actuation limitation on the ReaTHM testing setup for a particular pla...
Shu, Liang; Wu, Guichu; Chen, Dingfang; Dapino, Marcelo J.
2016-03-01
On active bending structures, the actuation direction and the excitation field direction are not the same. Simple lumped parameter models are inadequate to describe the relationship between output displacement and input field. In this paper, a dynamic distributed parameter model is presented to describe the system dynamics of a galfenol bending actuator. To consider nonlinearities and hysteresis in bending, a nonlinear magnetomechanical model is developed to characterize the hysteretic magnetostriction generated by the galfenol layer. A dynamic real-time control strategy is proposed to compensate for hysteresis. A nonlinear inverse filter is constructed to linearize the hysteresis based on the proposed distributed parameter model. In order to increase the calculation efficiency, a new iteration method is proposed to calculate the filter. The iteration stepsize of the input field can be adaptively updated according to the inverting error. Simulation results show that significant enhancement of convergence efficiency can be achieved by using the proposed method compared with the existing fixed step size method. Experiments have been conducted to verify the real-time control strategy.
Pusey, Jason L.; Yoo, Jin-Hyeong
2014-06-01
We document the design and preliminary numerical simulation study of a high fidelity model of Canid, a recently introduced bounding robot. Canid is a free-standing, power-autonomous quadrupedal machine constructed from standard commercially available electromechanical and structural elements, incorporating compliant C-shaped legs like those of the decade old RHex design, but departing from that standard (and, to the best of our knowledge, from any prior) robot platform in its parallel actuated elastic spine. We have used a commercial modeling package to develop a finite-element model of the actuated, cable-driven, rigid-plate-reinforced harness for the carbon-fiber spring that joins the robot's fore- and hind-quarters. We compare a numerical model of this parallel actuated elastic spine with empirical data from preliminary physical experiments with the most important component of the spine assembly: the composite leaf spring. Specifically, we report our progress in tuning the mechanical properties of a standard modal approximation to a conventional compliant beam model whose boundary conditions represent constraints imposed by the actuated cable driven vertebral plates that comprise the active control affordance over the spine. We conclude with a brief look ahead at near-term future experiments that will compare predictions of this fitted composite spring model with data taken from the physical spine flexed in isolation from the actuated harness.
Asymmetric surface dielectric barrier discharge (SDBD) plasma actuators have been intensely studied for a number of years due to their potential applications for aerodynamic control. In this paper, four types of actuators with different configurations of exposed electrode are proposed. The SDBD actuators investigated are driven by dual-power supply, referred to as a fixed AC high voltage and an adjustable DC bias. The effects of the electrode structures on the dielectric surface potential distribution, the electric wind velocity, and the mean thrust production are studied, and the dominative factors of airflow acceleration behavior are revealed. The results have shown that the actions of the SDBD actuator are mainly dependent on the geometry of the exposed electrode. Besides, the surface potential distribution can effectively affect the airflow acceleration behavior. With the application of an appropriate additional DC bias, the surface potential will be modified. As a result, the performance of the electric wind produced by a single SDBD can be significantly improved. In addition, the work also illustrates that the actuators with more negative surface potential present better mechanical performance
Analysis of Foot Slippage Effects on an Actuated Spring-mass Model of Dynamic Legged Locomotion
Yizhar Or
2016-04-01
Full Text Available The classical model of spring-loaded inverted pendulum (SLIP and its extensions have been widely accepted as a simple description of dynamic legged locomotion at various scales in humans, legged robots and animals. Similar to the majority of models in the literature, the SLIP model assumes ideal sticking contact of the foot. However, there are practical scenarios of low ground friction that causes foot slippage, which can have a significant influence on dynamic behaviour. In this work, an extension of the SLIP model with two masses and torque actuation is considered, which accounts for possible slippage under Coulomb’s friction law. The hybrid dynamics of this model is formulated and numerical simulations under representative parameter values reveal several types of stable periodic solutions with stick slip transitions. Remarkably, it is found that slippage due to low friction can sometimes increase average speed and improve energetic efficiency by significantly reducing the mechanical cost of transport.
Towards a model-based development approach for wireless sensor-actuator network protocols
Kumar S., A. Ajith; Simonsen, Kent Inge
2014-01-01
Model-Driven Software Engineering (MDSE) is a promising approach for the development of applications, and has been well adopted in the embedded applications domain in recent years. Wireless Sensor Actuator Networks consisting of resource constrained hardware and platformspecific operating system...... induced due to manual translations. With the use of formal semantics in the modeling approach, we can further ensure the correctness of the source model by means of verification. Also, with the use of network simulators and formal modeling tools, we obtain a verified and validated model to be used...... as a basis for code-generation. The aim is to build protocols with shorter design to implementation time and efforts, along with higher confidence in the protocol designed....
An Analytic Model for the Success Rate of a Robotic Actuator System in Hitting Random Targets
Stuart Bradley
2015-11-01
Full Text Available Autonomous robotic systems are increasingly being used in a wide range of applications such as precision agriculture, medicine, and the military. These systems have common features which often includes an action by an “actuator” interacting with a target. While simulations and measurements exist for the success rate of hitting targets by some systems, there is a dearth of analytic models which can give insight into, and guidance on optimization, of new robotic systems. The present paper develops a simple model for estimation of the success rate for hitting random targets from a moving platform. The model has two main dimensionless parameters: the ratio of actuator spacing to target diameter; and the ratio of platform distance moved (between actuator “firings” to the target diameter. It is found that regions of parameter space having specified high success are described by simple equations, providing guidance on design. The role of a “cost function” is introduced which, when minimized, provides optimization of design, operating, and risk mitigation costs.
Samadi, B; Achiche, S; Parent, A; Ballaz, L; Chouinard, U; Raison, M
2016-11-01
The use of exoskeletons as an aid for people with musculoskeletal disorder is the subject to an increasing interest in the research community. These devices are expected to meet the specific needs of users, such as children with cerebral palsy (CP) who are considered a significant population in pediatric rehabilitation. Although these exoskeletons should be designed to ease the movement of people with physical shortcoming, their design is generally based on data obtained from healthy adults, which leads to oversized components that are inadequate to the targeted users. Consequently, the objective of this study is to custom-size the lower limb exoskeleton actuators based on dynamic modeling of the human body for children with CP on the basis of hip, knee, and ankle joint kinematics and dynamics of human body during gait. For this purpose, a multibody modeling of the human body of 3 typically developed children (TD) and 3 children with CP is used. The results show significant differences in gait patterns especially in knee and ankle with respectively 0.39 and -0.33 (Nm/kg) maximum torque differences between TD children and children with CP. This study provides the recommendations to support the design of actuators to normalize the movement of children with CP. PMID:26980164
Numerical Simulation and Wake Modeling of Wind Turbine Rotor as AN Actuator Disk
Shen, Xiang; Wang, Tongguang; Zhong, Wei
Numerical simulations of flow fields around the wind turbine rotor simplified as an actuator disk (AD) with zero thickness have been made to investigate the flow structure and wake development in different operation states. A N-S solver has been used and the energy extracted by the rotor is represented by a discontinuous pressure jump through the actuator disk. Axial pressure and velocity development from far upstream to far downstream is fully described by the simulations, which could never be obtained by the momentum theory. It is showed that there are significant differences in wake development between inviscid and viscous conditions. In inviscid simulations, the axial velocity keeps decreasing along the oncoming flow direction, which is consistent with the momentum theory. In viscous simulations, however, the axial velocity first decreases but then gradually recovers approaching to the undisturbed velocity, due to momentum transport from outer flow to wake flow by viscous shear effect. Based on the numerical analysis, the work of this paper is also focused on wake modeling. A new two-dimensional models based on nonlinear wake development has been developed, which is capable to describe the far wake more accurately.
Bouchaala, Adam M.
2015-01-01
We investigate the dynamics of electrically actuated Micro and Nano (Carbon nanotube (CNT)) cantilever beams implemented as resonant sensors for mass detection of biological elements. The beams are modeled using an Euler-Bernoulli beam theory including the nonlinear electrostatic forces and the added biological elements, which are modeled as a discrete point mass. A multi-mode Galerkin procedure is utilized to derive a reduced-order model, which is used for the dynamic simulations. The frequency shifts due to added mass of Escherichia coli (E. coli) and Prostate Specific Antigen (PSA) are calculated for the primary and higher order modes of vibrations. Also, analytical expressions of the natural frequency shift under dc voltage and added mass have been developed. We found that using higher-order modes of vibration of MEMS beams or miniaturizing the size of the beam to Nano scale leads to significant improved sensitivity. © Springer International Publishing Switzerland 2015.
Two-spring model for active compression textiles with integrated NiTi coil actuators
This paper describes the development and implementation of a two-spring model to predict the performance of hybrid compression textiles combining passive elastic fabrics and integrated NiTi shape memory alloy (SMA) coil actuators. An analytic model that treats passive fabric-SMA coil systems as conjoined linear springs is presented to predict garment passive and active counter-pressure as a function of 11 design variables. For a fixed SMA coil design (encompassing five design variables), the model predicts that passive fabric material modulus, initial length, width and thickness determine both passive counter-pressure magnitude and activation stroke length, and that passive and active pressures are highly dependent on the relative unstretched lengths of the conjoined SMA-fabric system compared to the total limb circumference. Several passive fabrics were tested to determine their moduli and to generally assess the fabric linearity model assumption: two fabrics (spandex and neoprene) were found to behave linearly up to 200% strain, while two other fabrics (flat polyester elastic and a tri-laminate Lycra) were found to be nonlinear in the same strain envelope. Five hypothetical compression tourniquet designs are presented using experimentally determined fabric characteristics and previously studied SMA actuators developed at MIT. The performance of each tourniquet design is discussed with a specific focus on mechanical counter-pressure (MCP) space suit design requirements, with designs presented that achieve the full MCP design specification (> 29.6 kPa) while minimizing (< 5 mm) garment thickness. The modeling framework developed in this effort enables compression garment designers to tailor counter-pressure and activation stroke properties of active compression garments based on a variety of design parameters to meet a wide range of performance specifications. (paper)
Two-spring model for active compression textiles with integrated NiTi coil actuators
Holschuh, B.; Newman, D.
2015-03-01
This paper describes the development and implementation of a two-spring model to predict the performance of hybrid compression textiles combining passive elastic fabrics and integrated NiTi shape memory alloy (SMA) coil actuators. An analytic model that treats passive fabric-SMA coil systems as conjoined linear springs is presented to predict garment passive and active counter-pressure as a function of 11 design variables. For a fixed SMA coil design (encompassing five design variables), the model predicts that passive fabric material modulus, initial length, width and thickness determine both passive counter-pressure magnitude and activation stroke length, and that passive and active pressures are highly dependent on the relative unstretched lengths of the conjoined SMA-fabric system compared to the total limb circumference. Several passive fabrics were tested to determine their moduli and to generally assess the fabric linearity model assumption: two fabrics (spandex and neoprene) were found to behave linearly up to 200% strain, while two other fabrics (flat polyester elastic and a tri-laminate Lycra) were found to be nonlinear in the same strain envelope. Five hypothetical compression tourniquet designs are presented using experimentally determined fabric characteristics and previously studied SMA actuators developed at MIT. The performance of each tourniquet design is discussed with a specific focus on mechanical counter-pressure (MCP) space suit design requirements, with designs presented that achieve the full MCP design specification (\\gt 29.6 kPa) while minimizing (\\lt 5 mm) garment thickness. The modeling framework developed in this effort enables compression garment designers to tailor counter-pressure and activation stroke properties of active compression garments based on a variety of design parameters to meet a wide range of performance specifications.
Enhanced Dynamic Model of Pneumatic Muscle Actuator with Elman Neural Network
Alexander Hošovský
2015-01-01
Full Text Available To make effective use of model-based control system design techniques, one needs a good model which captures system’s dynamic properties in the range of interest. Here an analytical model of pneumatic muscle actuator with two pneumatic artificial muscles driving a rotational joint is developed. Use of analytical model makes it possible to retain the physical interpretation of the model and the model is validated using open-loop responses. Since it was considered important to design a robust controller based on this model, the effect of changed moment of inertia (as a representation of uncertain parameter was taken into account and compared with nominal case. To improve the accuracy of the model, these effects are treated as a disturbance modeled using the recurrent (Elman neural network. Recurrent neural network was preferred over feedforward type due to its better long-term prediction capabilities well suited for simulation use of the model. The results confirm that this method improves the model performance (tested for five of the measured variables: joint angle, muscle pressures, and muscle forces while retaining its physical interpretation.
Computational design and multiscale modeling of a nanoactuator using DNA actuation
Developments in the field of nano-biodevices coupling nanostructures and biological components are of great interest in medical nanorobotics. As the fundamentals of bio/non-bio interaction processes are still poorly understood in the design of these devices, design tools and multiscale dynamics modeling approaches are necessary at the fabrication pre-project stage. This paper proposes a new concept of optimized carbon nanotube based servomotor design for drug delivery and biomolecular transport applications. The design of an encapsulated DNA-multi-walled carbon nanotube actuator is prototyped using multiscale modeling. The system is parametrized by using a quantum level approach and characterized by using a molecular dynamics simulation. Based on the analysis of the simulation results, a servo nanoactuator using ionic current feedback is simulated and analyzed for application as a drug delivery carrier.
Analysis of VAWT aerodynamics and design using the Actuator Cylinder flow model
Aagaard Madsen, Helge; Schmidt Paulsen, Uwe; Vita, Luca
2014-01-01
The actuator cylinder (AC) flow model is defined as the ideal VAWT rotor. Radial directed volume forces are applied on the circular path of the VAWT rotor airfoil and constitute an energy conversion in the flow. The power coefficient for the ideal as well as the real energy conversion is defined...... maximum power coefficient for the ideal energy conversion of a VAWT could exceed the Betz limit. The real energy conversion of the 5MW DeepWind rotor is simulated with the AC flow model in combination with the blade element analysis. Aerodynamic design aspects are discussed on this basis revealing that...... the maximum obtainable power coefficient for a fixed pitch VAWT is constrained by the fundamental cyclic variation of inflow angle and relative velocity leading to a loading that deviates considerably from the uniform loading....
Analysis of VAWT aerodynamics and design using the Actuator Cylinder flow model
Aagaard Madsen, Helge; Schmidt Paulsen, Uwe; Vita, Luca
2012-01-01
The actuator cylinder flow model is defined as the ideal VAWT rotor. Radial directed volume forces are applied on the circular path of the VAWT rotor airfoil and constitute an energy conversion in the flow. The power coefficient for the ideal as well as the real energy conversion is defined. The...... coefficient for the ideal energy conversion of a VAWT could exceed the Betz limit. The real energy conversion of the 5MW DeepWind rotor is simulated with the AC flow model in combination with the blade element analysis. Aerodynamic design aspects are discussed on this basis revealing that the maximum...... obtainable power coefficient for a fixed pitch VAWT is constrained by the fundamental cyclic variation of inflow angle and relative velocity leading to a loading that deviates considerably from the uniform loading....
Habib, Tufail
In an electromechanical valve actuated engine, the valves are driven by solenoid-type actuators and cam-shaft is eliminated. Control of each valve provides flexibility in valve timings over all engine conditions and achieves the benefits of variable valve timing(VVT). This paper is about investig......In an electromechanical valve actuated engine, the valves are driven by solenoid-type actuators and cam-shaft is eliminated. Control of each valve provides flexibility in valve timings over all engine conditions and achieves the benefits of variable valve timing(VVT). This paper is about...... investigation of Electro-mechanical actuator at simulated pressure conditions for a single cylinder engine. For this purpose, a scaled down actuator with reduced armature lift and high stiffness springs are being used. Experiments are conducted to measure valve release timings, transition times and contact...
Singh, Yadvinder
2013-01-01
Piezoelectric actuators are increasingly used for the electronic control of fuel injector opening valves. Hydrogen is considered an attractive clean alternative fuel for automobile and power generation applications. Current understanding of the performance of piezoelectric actuators in a hydrogen environment is very limited. This work is aimed at experimentally investigating the performance of hydrogen-exposed piezoelectric actuators under conditions directly relevant to a hydrogen-based fuel...
Modeling of effects of matrix on actuation characteristics of embedded shape memory alloy wires
CUI Xiao-long; ZHENG Yan-jun; CUI Li-shan
2005-01-01
Effects of matrix properties on the actuation characteristics of embedded shape memory alloy wires were studied. The coefficient of thermal expansion and the modulus of matrix have significant effect on the maximum recovery stress. The thermal strain rate of the SMA wires upon heating is more sensitive to the matrix properties than the stress rate does. Additional fibers embedded in the matrix have significant effect on the stress distribution between the SMA wires and the matrix, and thus affect the interface quality significantly. Fibers with negative thermal expansion coefficient are beneficial to the interface between shape memory alloy wires and the epoxy matrix. All conclusions based on the numerical modeling can find experimental supports.
Biological tentacles, such as octopus arms, have entirely flexible structures and virtually infinite degrees of freedom (DOF) that allow for elongation, shortening and bending at any point along the arm length. The amazing dexterity of biological tentacles has driven the growing implementation of continuum manipulators in robotic systems. This paper presents a pneumatic manipulator inspired by biological continuum structures in some of their key features and functions, such as continuum morphology, intrinsic compliance and stereotyped motions with hyper redundant DOF. The kinematics and dynamics of the manipulator are formulated and identified, and a hierarchical controller taking inspiration from the structure of an octopus nervous system is used to relate desired stereotyped motions to individual actuator inputs. Simulations and experiments are carried out to validate the model and prototype where good agreement was found between the two. (paper)
In this paper, a complete nonlinear finite element model for coupled-domain MEMS devices with electrostatic actuation and squeeze film effect is developed. For this purpose, a corotational finite element formulation for the dynamic analysis of planer Euler beams is employed. In this method, the internal nodal forces due to deformation and intrinsic residual stresses, the inertial nodal forces, and the damping effect of squeezed air film are systematically derived by consistent linearization of the fully geometrically nonlinear beam theory using d'Alamber and virtual work principles. An incremental-iterative method based on the Newmark direct integration procedure and the Newton-Raphson algorithm is used to solve the nonlinear dynamic equilibrium equations. Numerical examples are presented and compared with experimental findings which indicate properly good agreement
Development of Traveling Wave Actuators Using Waveguides of Different Geometrical Forms
Ramutis Bansevicius
2016-01-01
Full Text Available The paper covers the research and development of piezoelectric traveling wave actuators using different types of the waveguides. The introduced piezoelectric actuators can be characterized by specific areas of application, different resolution, and torque. All presented actuators are ultrasonic resonant devices and they were developed to increase amplitudes of the traveling wave oscillations of the contact surface. Three different waveguides are introduced, that is, symmetrical, asymmetrical, and cone type waveguide. A piezoelectric ring with the sectioned electrodes is used to excite traveling wave oscillations for all actuators. Operating principle, electrode pattern, and excitation regimes of piezoelectric actuators are described. A numerical modelling of the actuators was performed to validate the operating principle and to calculate trajectories of the contact points motion. Prototype actuators were made and experimental study was performed. The results of numerical and experimental analysis are discussed.
A nonlinear, control-oriented model for ionic polymer–metal composite actuators
Ionic polymer–metal composites (IPMCs) form an important category of electroactive polymers and have many potential applications in biomedical, robotic and micro/nanomanipulation systems. In this paper, a nonlinear, control-oriented model is proposed for IPMC actuators. A key component in the proposed model is the nonlinear capacitance of the IPMC. A nonlinear partial differential equation (PDE), which can capture the fundamental physics in the IPMC, is fully considered in the derivation of nonlinear capacitance. A systems perspective is taken to get the nonlinear mapping from the voltage to the induced charge by analytically solving the nonlinear PDE at the steady state when a step voltage is applied. The nonlinear capacitance is incorporated into a circuit model, which includes additionally the pseudocapacitance due to the electrochemical adsorption process, the ion diffusion resistance, and the nonlinear DC resistance of the polymer, to capture electrical dynamics of the IPMC. With electromechanical coupling, the curvature output is derived based on the circuit model. The proposed model is formulated in the state space, which will be the starting point for nonlinear controller design. Experimental verification shows that the proposed model can capture the major nonlinearities in the electrical response of the IPMC
Modeling and Application of Series Elastic Actuators for Force Control Multi Legged Robots
S, Arumugom; V, Ponselvan
2009-01-01
Series Elastic Actuators provide many benefits in force control of robots in unconstrained environments. These benefits include high force fidelity, extremely low impedance, low friction, and good force control bandwidth. Series Elastic Actuators employ a novel mechanical design architecture which goes against the common machine design principal of "stiffer is better". A compliant element is placed between the gear train and driven load to intentionally reduce the stiffness of the actuator. A position sensor measures the deflection, and the force output is accurately calculated using Hooke's Law (F=Kx). A control loop then servos the actuator to the desired output force. The resulting actuator has inherent shock tolerance, high force fidelity and extremely low impedance. These characteristics are desirable in many applications including legged robots, exoskeletons for human performance amplification, robotic arms, haptic interfaces, and adaptive suspensions. We describe several variations of Series Elastic Ac...
Buoso, Stefano; Palacios, Rafael
2016-04-01
This work presents a numerical framework for the simulation and design of integrally actuated membrane wings with feedback control. The performance of the aeroelastic system are evaluated using a high-fidelity model. It consists in a fluid solver based on the direct numerical integration of the unsteady Navier-Stokes equations implicitly coupled with a geometrically non-linear dynamic structural model which has been calibrated using experimental data. The rate-dependent constitutive law for the dielectric elastomer considered for the integral wing actuation is based on a non-linear formulation. The framework also includes a methodology for the model reduction of the fully-coupled system. The resulting low-order description showed to retain the main system dynamics, and can therefore be used for the design of the control scheme for the wing. Results highlights the potential to achieve on-demand aerodynamics using the actuation concept proposed. In particular, it is shown that the wing aerodynamic performance is noticeably enhanced through the actuation and the disturbances on the lift in case of gusts can be reduced up to 60%.
Al-Taie, Fatimah; Werner, Herbert
2016-06-01
A technique for model reduction of exponentially stable spatially interconnected systems is presented, where the order of the reduced model is determined by the number of truncated small generalised singular values of the structured solutions to a pair of Lyapunov inequalities. For parameter-invariant spatially interconnected systems, the technique is based on solving a pair of Lyapunov inequalities in continuous-time and -space domain with a rank constraint. Using log-det and cone complementarity methods, an improved error bound can be obtained. The approach is extended to spatially parameter-varying systems, and a balanced truncation approach using parameter-dependent Gramians is proposed to reduce the conservatism caused by the use of constant Gramians. This is done by considering two important operators, which can be used to represent multidimensional systems (temporal- and spatial-linear parameter varying interconnected systems). The results are illustrated with their application to an experimentally identified spatially interconnected model of an actuated beam; the experimentally obtained response to an excitation signal is compared with the response predicted by a reduced model.
Saggam Narendar
2011-07-01
Full Text Available In this study, a rotating single-walled carbon nanotube (SWCNT is modelled as an Euler-Bernoulli beam using the non-local/non-classical continuum mechanics. These rotating SWCNTs are used in nanoscale rotational actuators. The mathematical model has been used to study the wave behaviour in rotating SWCNTs. The governingpartial differential equation for a uniform rotating beam is derived incorporating the non-local scale effects. The spatial variation in centrifugal force has been modelled in an average sense. Even though this averaging seems to be a crude approximation, one can use this as a powerful model in analysing the wave dispersion characteristics ofthe rotating CNTs. Spectrum and dispersion curves as a function of rotating speed and non-local scaling parameter were obtained. It has been shown that the dispersive ﬂexural wave tends to behave non-dispersively at very high rotation speeds. The numerical results have been simulated for a rotating SWCNT as a waveguide.Defence Science Journal, 2011, 61(4, pp.317-324, DOI:http://dx.doi.org/10.14429/dsj.61.1091
Boz, Utku; Basdogan, Ipek
2015-12-01
Structural vibrations is a major cause for noise problems, discomfort and mechanical failures in aerospace, automotive and marine systems, which are mainly composed of plate-like structures. In order to reduce structural vibrations on these structures, active vibration control (AVC) is an effective approach. Adaptive filtering methodologies are preferred in AVC due to their ability to adjust themselves for varying dynamics of the structure during the operation. The filtered-X LMS (FXLMS) algorithm is a simple adaptive filtering algorithm widely implemented in active control applications. Proper implementation of FXLMS requires availability of a reference signal to mimic the disturbance and model of the dynamics between the control actuator and the error sensor, namely the secondary path. However, the controller output could interfere with the reference signal and the secondary path dynamics may change during the operation. This interference problem can be resolved by using an infinite impulse response (IIR) filter which considers feedback of the one or more previous control signals to the controller output and the changing secondary path dynamics can be updated using an online modeling technique. In this paper, IIR filtering based filtered-U LMS (FULMS) controller is combined with online secondary path modeling algorithm to suppress the vibrations of a plate-like structure. The results are validated through numerical and experimental studies. The results show that the FULMS with online secondary path modeling approach has more vibration rejection capabilities with higher convergence rate than the FXLMS counterpart.
Analysis of VAWT aerodynamics and design using the Actuator Cylinder flow model
The actuator cylinder (AC) flow model is defined as the ideal VAWT rotor. Radial directed volume forces are applied on the circular path of the VAWT rotor airfoil and constitute an energy conversion in the flow. The power coefficient for the ideal as well as the real energy conversion is defined. The describing equations for the two-dimensional AC model are presented and a solution method splitting the final solution in a linear and non-linear part is briefly described. A family of loadforms approaching the uniform loading is used to study the ideal energy conversion indicating that the maximum power coefficient for the ideal energy conversion of a VAWT could exceed the Betz limit. The real energy conversion of the 5MW DeepWind rotor is simulated with the AC flow model in combination with the blade element analysis. Aerodynamic design aspects are discussed on this basis revealing that the maximum obtainable power coefficient for a fixed pitch VAWT is constrained by the fundamental cyclic variation of inflow angle and relative velocity leading to a loading that deviates considerably from the uniform loading
Liang, Binbin; Zhang, Long; Wang, Binglei; Zhou, Shenjie
2015-07-01
A size-dependent model for the electrostatically actuated Nano-Electro-Mechanical Systems (NEMS) incorporating nonlinearities and Casimir force is presented by using a variational method. The governing equation and boundary conditions are derived with the help of strain gradient elasticity theory and Hamilton principle. Generalized differential quadrature (GDQ) method is employed to solve the problem numerically. The pull-in instability with Casimir force included is then studied. The results reveal that Casimir force, which is a spontaneous force between the two electrodes, can reduce the external applied voltage. With Casimir force incorporated, the pull-in instability occurs without voltage applied when the beam size is in nanoscale. The minimum gap and detachment length can be calculated from the present model for different beam size, which is important for NEMS design. Finally, discussions of size effect induced by the strain gradient terms reveal that the present model is more accurate since size effect play an important role when beam in nanoscale.
Analysis of VAWT aerodynamics and design using the Actuator Cylinder flow model
Madsen, H. Aa; Paulsen, U. S.; Vitae, L.
2014-12-01
The actuator cylinder (AC) flow model is defined as the ideal VAWT rotor. Radial directed volume forces are applied on the circular path of the VAWT rotor airfoil and constitute an energy conversion in the flow. The power coefficient for the ideal as well as the real energy conversion is defined. The describing equations for the two-dimensional AC model are presented and a solution method splitting the final solution in a linear and non-linear part is briefly described. A family of loadforms approaching the uniform loading is used to study the ideal energy conversion indicating that the maximum power coefficient for the ideal energy conversion of a VAWT could exceed the Betz limit. The real energy conversion of the 5MW DeepWind rotor is simulated with the AC flow model in combination with the blade element analysis. Aerodynamic design aspects are discussed on this basis revealing that the maximum obtainable power coefficient for a fixed pitch VAWT is constrained by the fundamental cyclic variation of inflow angle and relative velocity leading to a loading that deviates considerably from the uniform loading.
Minimizing actuator-induced errors in active space telescope mirrors
Smith, Matthew W.; Miller, David W.
2010-07-01
The trend in future space telescopes points toward increased primary mirror diameter, which improves resolution and sensitivity. However, given the constraints on mass and volume deliverable to orbit by current launch vehicles, creative design solutions are needed to enable increased mirror size while keeping mass and volume within acceptable limits. Lightweight, segmented, rib-stiffened, actively controlled primary mirrors have emerged as a potential solution. Embedded surface-parallel actuators can be used to change the mirror prescription onorbit, lowering mirror mass overall by enabling lighter substrate materials such as silicon carbide (SiC) and relaxing manufacturing constraints. However, the discrete nature of the actuators causes high spatial frequency residual errors when commanding low-order prescription changes. A parameterized finite element model is used to simulate actuator-induced residual error and investigate design solutions that mitigate this error source. Judicious specification of mirror substrate geometry and actuator length is shown to reduce actuator-induced residual while keeping areal density constant. Specifically, a sinusoidally-varying rib shaping function is found to increase actuator influence functions and decrease residual. Likewise, longer actuators are found to offer reduced residual. Other options for geometric shaping are discussed, such as rib-to-facesheet blending and the use of two dimensional patch actuators.
A Roll Controlling Approach for a Simple Dual-Actuated Flapping Aerial Vehicle Model
Labib Omar El-Farouk E.
2016-01-01
Full Text Available Aerial vehicles have been investigated recently in different contexts, due to their high potential of utilization in multiple application areas. Different mechanisms can be used for aerial vehicles actuation, such as the rotating multi-blade systems (Multi-Copters and more recently flapping wings. Flapping wing robots have attracted much attention from researchers in recent years. In this study, a simple dual-actuated flapping mechanism is proposed for actuating a flapping wing robot. The mechanism is designed, simulated and validated in both simulation and experiments. A roll controlling approach is proposed to control the roll angle of the robot via controlling the speeds of both motors actuating each of the wings. The results achieved are validated experimentally, and are promising opening the door for further investigation using our proposed system
Mathematical and Computer Modelling of DC Actuator-Based Linear Drives
Doležel, Ivo; Škopek, M.; Ulrych, B.; Vostracký, Z.
2002-01-01
Roč. 1, - (2002), s. 29-33 Institutional research plan: CEZ:AV0Z2057903 Keywords : DC actuators * electromagnetic field * temperature field Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering
Jacobs, William R.; Wilson, Emma D.; Assaf, Tareq; Rossiter, Jonathan; Dodd, Tony J.; Porrill, John; Anderson, Sean R.
2015-05-01
Current models of dielectric elastomer actuators (DEAs) are mostly constrained to first principal descriptions that are not well suited to the application of control design due to their computational complexity. In this work we describe an integrated framework for the identification of control focused, data driven and time-varying DEA models that allow advanced analysis of nonlinear system dynamics in the frequency-domain. Experimentally generated input-output data (voltage-displacement) was used to identify control-focused, nonlinear and time-varying dynamic models of a set of film-type DEAs. The model description used was the nonlinear autoregressive with exogenous input structure. Frequency response analysis of the DEA dynamics was performed using generalized frequency response functions, providing insight and a comparison into the time-varying dynamics across a set of DEA actuators. The results demonstrated that models identified within the presented framework provide a compact and accurate description of the system dynamics. The frequency response analysis revealed variation in the time-varying dynamic behaviour of DEAs fabricated to the same specifications. These results suggest that the modelling and analysis framework presented here is a potentially useful tool for future work in guiding DEA actuator design and fabrication for application domains such as soft robotics.
Rajappa, Sujit; Ryll, Markus; Heinrich H Bülthoff; Franchi, Antonio
2015-01-01
International audience Mobility of a hexarotor UAV in its standard configuration is limited, since all the propeller force vectors are parallel and they achieve only 4 DoF actuation, similar, e.g., to quadrotors. As a consequence, the hexarotor pose cannot track an arbitrary trajectory over time. In this paper, we consider a different hexarotor architecture where propellers are tilted, without the need of any additional hardware. In this way, the hexarotor possess a 6 DoF actuation which a...
Modeling and experiment of three-degree-of-freedom actuators using piezoelectric buzzers
This study presents innovative three-degree-of-freedom piezoelectric actuators. Under the piezoelectric force and dry friction, the piezoelectric actuators not only can move in the Z-axis direction, but also rotate around the Y-axis and Z-axis. The Z-axis displacement can reach 62 mm and the rotation angle around the Y-axis and Z-axis can reach 270° and 360°, respectively. Compared with the literature, this innovative actuator design achieves one-degree-of-freedom translation and two-degree-of-freedom rotation. Equations of motion are derived based on the piezoelectric properties and Newton’s law. Two types of actuators are created in this study. In the first type, the centers of four piezoelectric buzzers are attached to an arm while in the other type each rim of the four piezoelectric buzzers is attached to the arm. Experimental results are compared with theoretical results. According to the experimental results, the present actuator can accomplish a translational velocity of 11 mm s−1, a Y-axis angular velocity of 8.96 rad s−1, a Z-axis angular velocity of 2.63 rad s−1, and a force of 2.49 mN. By using four piezoelectric buzzers, this study creates piezoelectric actuators capable of both translational and rotational motions. (paper)
Modular Architecture of a Non-Contact Pinch Actuation Micropump
Ruzairi Abdul Rahim; Pei Ling Leow; Uda Hashim; Tijjani Adam; Rashidah Arsat; Pei Song Chee
2012-01-01
This paper demonstrates a modular architecture of a non-contact actuation micropump setup. Rapid hot embossing prototyping was employed in micropump fabrication by using printed circuit board (PCB) as a mold material in polymer casting. Actuator-membrane gap separation was studied, with experimental investigation of three separation distances: 2.0 mm, 2.5 mm and 3.5 mm. To enhance the micropump performance, interaction surface area between plunger and membrane was modeled via finite element a...
The CFD Investigation of Two Non-Aligned Turbines Using Actuator Disk Model and Overset Grids
In this study flow over two axially non-aligned wind turbines is investigated via 3-D CFD analysis by solving Navier-Stokes equations. This setting is the test case geometry for the NTNU's ''Blind-Test'' Workshop 3 (BT3) and it aims to predict the performance of the wind turbines and their wake development under asymmetrical flow conditions. The performance of the turbine in the wake of the other turbine is numerically studied for different tip speed ratios. The measurements of velocity profile which is severely disturbed by both turbines are also carried out at the several locations of the wind tunnel. The computational results for NTNU wind turbine test case were obtained by 3-D CFD simulations with two different approaches. The first approach is to employ the actuator disk model, which is used in order to approximate the pressure jump across the rotor disk to simulate the impact of the wind turbines. At the second approach, the actual geometry of the turbine rotor was used, and the rotor blades were rotated using an overset grid methodology over the background grids. The thrust coefficients and the velocity profiles are calculated with two different approaches and the results are compared to experimental data presented in BT3
Model identification of terfenol-D magnetostrictive actuator for precise positioning control
Saleem, Ashraf; Ghodsi, Mojtaba; Mesbah, Mostefa; Ozer, Abdullah
2016-04-01
Feedback control strategies are desirable for disturbance rejection of human-induced vibrations in civil engineering structures as human walking forces cannot easily be measured. In relation to human-induced vibration control studies, most past researches have focused on floors and footbridges and the widely used linear controller implemented in the trials has been the direct velocity feedback (DVF) scheme. With appropriate compensation to enhance its robustness, it has been shown to be effective at damping out the problematic modes of vibration of the structures in which the active vibration control systems have been implemented. The work presented here introduces a disturbance observer (DOB) that is used with an outer-loop DVF controller. Results of analytical studies presented in this work based on the dynamic properties of a walkway bridge structure demonstrate the potential of this approach for enhancing the vibration mitigation performance offered by a purely DVF controller. For example, estimates of controlled frequency response functions indicate improved attenuation of vibration around the dominant frequency of the walkway bridge structure as well as at higher resonant frequencies. Controlled responses from three synthesized walking excitation forces on a walkway bridge structure model show that the inclusion of the disturbance observer with an outer loop DVF has potential to improve on the vibration mitigation performance by about 3.5% at resonance and 6-10% off-resonance. These are realised with hard constraints being imposed on the low frequency actuator displacements.
Identification of a nonlinear black-box model for a self-sensing polymer metal composite actuator
An ion polymer metal composite (IPMC) is an electro-active polymer that bends in response to a small applied electrical field as a result of the mobility of cations in the polymer network and vice versa. The aim of this paper is the identification of a novel accurate nonlinear black-box model (NBBM) for IPMC actuators with self-sensing behavior based on a recurrent multi-layer perceptron neural network (RMLPNN) and a self-adjustable learning mechanism (SALM). Firstly, an IPMC actuator is investigated. Driving voltage signals are applied to the IPMC in order to identify the IPMC characteristics. Secondly, the advanced NBBM for the IPMC is built with suitable inputs and output to estimate the IPMC tip displacement. Finally, the model parameters are optimized by the collected input/output training data. Modeling results show that the proposed self-sensing methodology based on the optimized NBBM model can well describe the bending behavior of the IPMC actuator corresponding to its applied power without using any measuring sensor
Finite element analysis and validation of dielectric elastomer actuators used for active origami
The field of active origami explores the incorporation of active materials into origami-inspired structures in order to serve as a means of actuation. Active origami-inspired structures capable of folding into complex three-dimensional (3D) shapes have the potential to be lightweight and versatile compared to traditional methods of actuation. This paper details the finite element analysis and experimental validation of unimorph actuators. Actuators are fabricated by adhering layers of electroded dielectric elastomer (3M VHB F9473PC) onto a passive substrate layer (3M Magic Scotch Tape). Finite element analysis of the actuators simulates the electromechanical coupling of the dielectric elastomer under an applied voltage by applying pressures to the surfaces of the dielectric elastomer where the compliant electrode (conductive carbon grease) is present. 3D finite element analysis of the bending actuators shows that applying contact boundary conditions to the electroded region of the active and passive layers provides better agreement to experimental data compared to modeling the entire actuator as continuous. To improve the applicability of dielectric elastomer-based actuators for active origami-inspired structures, folding actuators are developed by taking advantage of localized deformation caused by a passive layer with non-uniform thickness. Two-dimensional analysis of the folding actuators shows that agreement to experimental data diminishes as localized deformation increases. Limitations of using pressures to approximate the electromechanical coupling of the dielectric elastomer under an applied electric field and additional modeling considerations are also discussed. (paper)
Lindner, Gerhard
2008-06-01
The propagation of surface acoustic waves (SAWs) along solid-liquid interfaces depends sensitively on the properties of the liquid covering the solid surface and may result in a momentum transfer into the liquid and thus a propulsion effect via acoustic streaming. This review gives an overview of the design of different SAW devices used for the sensing of liquids and the basic mechanisms of the interaction of SAWs with overlaying liquids. In addition, applications of devices based on these phenomena with respect to touch sensing and the measurement of liquid properties such as density, viscosity or the composition of mixed liquids are described, including microfabricated as well as macroscopic devices made from non-piezoelectric materials. With respect to the rapidly growing field of acoustic streaming applications, recent developments in the movement of nanolitre droplets on a single piezoelectric chip, the rather macroscopic approaches to the acoustic pumping of liquids in channels and recent attempts at numerical simulations of acoustic streaming are reported.
Sensors and actuators based on surface acoustic waves propagating along solid-liquid interfaces
The propagation of surface acoustic waves (SAWs) along solid-liquid interfaces depends sensitively on the properties of the liquid covering the solid surface and may result in a momentum transfer into the liquid and thus a propulsion effect via acoustic streaming. This review gives an overview of the design of different SAW devices used for the sensing of liquids and the basic mechanisms of the interaction of SAWs with overlaying liquids. In addition, applications of devices based on these phenomena with respect to touch sensing and the measurement of liquid properties such as density, viscosity or the composition of mixed liquids are described, including microfabricated as well as macroscopic devices made from non-piezoelectric materials. With respect to the rapidly growing field of acoustic streaming applications, recent developments in the movement of nanolitre droplets on a single piezoelectric chip, the rather macroscopic approaches to the acoustic pumping of liquids in channels and recent attempts at numerical simulations of acoustic streaming are reported. (topical review)
Ruzziconi, Laura
2013-06-10
We present a study of the dynamic behavior of a microelectromechanical systems (MEMS) device consisting of an imperfect clamped-clamped microbeam subjected to electrostatic and electrodynamic actuation. Our objective is to develop a theoretical analysis, which is able to describe and predict all the main relevant aspects of the experimental response. Extensive experimental investigation is conducted, where the main imperfections coming from microfabrication are detected, the first four experimental natural frequencies are identified and the nonlinear dynamics are explored at increasing values of electrodynamic excitation, in a neighborhood of the first symmetric resonance. Several backward and forward frequency sweeps are acquired. The nonlinear behavior is highlighted, which includes ranges of multistability, where the nonresonant and the resonant branch coexist, and intervals where superharmonic resonances are clearly visible. Numerical simulations are performed. Initially, two single mode reduced-order models are considered. One is generated via the Galerkin technique, and the other one via the combined use of the Ritz method and the Padé approximation. Both of them are able to provide a satisfactory agreement with the experimental data. This occurs not only at low values of electrodynamic excitation, but also at higher ones. Their computational efficiency is discussed in detail, since this is an essential aspect for systematic local and global simulations. Finally, the theoretical analysis is further improved and a two-degree-of-freedom reduced-order model is developed, which is also capable of capturing the measured second symmetric superharmonic resonance. Despite the apparent simplicity, it is shown that all the proposed reduced-order models are able to describe the experimental complex nonlinear dynamics of the device accurately and properly, which validates the proposed theoretical approach. © 2013 IOP Publishing Ltd.
We present a study of the dynamic behavior of a microelectromechanical systems (MEMS) device consisting of an imperfect clamped–clamped microbeam subjected to electrostatic and electrodynamic actuation. Our objective is to develop a theoretical analysis, which is able to describe and predict all the main relevant aspects of the experimental response. Extensive experimental investigation is conducted, where the main imperfections coming from microfabrication are detected, the first four experimental natural frequencies are identified and the nonlinear dynamics are explored at increasing values of electrodynamic excitation, in a neighborhood of the first symmetric resonance. Several backward and forward frequency sweeps are acquired. The nonlinear behavior is highlighted, which includes ranges of multistability, where the nonresonant and the resonant branch coexist, and intervals where superharmonic resonances are clearly visible. Numerical simulations are performed. Initially, two single mode reduced-order models are considered. One is generated via the Galerkin technique, and the other one via the combined use of the Ritz method and the Padé approximation. Both of them are able to provide a satisfactory agreement with the experimental data. This occurs not only at low values of electrodynamic excitation, but also at higher ones. Their computational efficiency is discussed in detail, since this is an essential aspect for systematic local and global simulations. Finally, the theoretical analysis is further improved and a two-degree-of-freedom reduced-order model is developed, which is also capable of capturing the measured second symmetric superharmonic resonance. Despite the apparent simplicity, it is shown that all the proposed reduced-order models are able to describe the experimental complex nonlinear dynamics of the device accurately and properly, which validates the proposed theoretical approach. (paper)
Highlights: • Estimation of aerodynamic force on variable turbine geometry vanes and actuator. • Method based on exhaust gas flow modeling. • Simulation tool for integration of aerodynamic force in automotive simulation software. - Abstract: This paper provides a reliable tool for simulating the effects of exhaust gas flow through the variable turbine geometry section of a variable geometry turbocharger (VGT), on flow control mechanism. The main objective is to estimate the resistive aerodynamic force exerted by the flow upon the variable geometry vanes and the controlling actuator, in order to improve the control of vane angles. To achieve this, a 1D model of the exhaust flow is developed using Navier–Stokes equations. As the flow characteristics depend upon the volute geometry, impeller blade force and the existing viscous friction, the related source terms (losses) are also included in the model. In order to guarantee stability, an implicit numerical solver has been developed for the resolution of the Navier–Stokes problem. The resulting simulation tool has been validated through comparison with experimentally obtained values of turbine inlet pressure and the aerodynamic force as measured at the actuator shaft. The simulator shows good compliance with experimental results
JAKUBCZAK II,JEROME F.; KRYGOWSKI,THOMAS W.; MILLER,SAMUEL L.; RODGERS,M. STEVEN; SNIEGOWSKI,JEFFRY J.
1999-09-22
The design, fabrication and characterization of a low-voltage rotary stepper motor are presented in this work. Using a five-level polysilicon MEMS technology, steps were taken to increase the capacitance over previous stepper motor designs to generate high torque at low voltages. A low-friction hub was developed to minimize frictional loads due to rubbing surfaces, producing an estimated resistive torque of about 6 pN-m. This design also allowed investigations into the potential benefit of using hard materials such as silicon nitride for lining of both the stationary and rotating hub components. The result is an electrostatic stepper motor capable of operation at less than six volts.
Zhu, Wei; Bian, Leixiang; An, Yi; Chen, Gangli; Rui, Xiaoting
2015-07-01
This paper outlines an optical beam steering system built using a two-axis fast steering mirror (FSM) with piezoelectric stack actuators to maintain precise pointing control. A novel mathematical model of the FSM is put forward by using a transfer matrix method of a multibody system to describe the dynamics characteristics and a hysteresis model to represent the hysteresis. Based on the proposed model, a model-based hybrid control is applied to force the output angle of the FSM to track the laser beam accurately thereafter. The experimental results are in accordance with the theoretical analysis. The results highlight significantly improved accuracy in the beam tracking control of the FSM.
Gan, Jinqiang; Zhang, Xianmin; Wu, Heng
2016-03-01
In this paper, a generalized hysteresis model is developed to describe both rate-independent and rate-dependent hysteresis in piezoelectric actuators. Based on the classical Prandtl-Ishlinskii (P-I) model, the developed model adds a quadratic polynomial and makes other small changes. When it is used to describe rate-independent hysteresis, the parameters of the model are constants, which can be identified by self-adaptive particle swarm optimization. The effectiveness of this rate-independent modified P-I model is demonstrated by comparing simulation results of the developed model and the classic Prandtl-Ishlinskii model. Simulation results suggest that the rate-independent modified P-I model can describe hysteresis more precisely. Compared with the classical P-I model, the rate-independent modified P-I model reduces modeling error by more than 50%. When it is used to describe rate-independent hysteresis, a one-side operator is adopted and the parameters are functions with input frequency. The results of the experiments and simulations have shown that the proposed models can accurately describe both rate-independent and rate-dependent hysteresis in piezoelectric actuators.
Modelling the effect of actuator-like behavior in dielectric elastomer generators
Zanini, P.; Rossiter, J.; Homer, M.
2015-10-01
Dielectric Elastomer Generators (DEGs) have been claimed as one promising technology for renewable mechanical to electrical energy harvesting, due to their lightweight, low cost, and high energy density. Dielectric elastomers have a dual behavior, able to convert electrical energy into mechanical if charged electrostatically and to convert mechanical to electrical energy if stretched and relaxed in a cycle that exploits its capacitance change. During such energy harvesting cycles, the material needs an electrical energy bias to be able to convert mechanical work into electrical energy, which produces an actuator behavior on the DEG that results in losses and decreases its performance. In this paper, we investigate this actuation behavior and its effect on energy harvesting in the DEGs. We compare two different charging methods and show that a constant voltage method can increase the net energy harvested by 5 times, despite the unwanted actuation effect.
Song, Yan; Fang, Xiaosheng; Diao, Qingda
2016-03-01
In this paper, we discuss the mixed H2/H∞ distributed robust model predictive control problem for polytopic uncertain systems subject to randomly occurring actuator saturation and packet loss. The global system is decomposed into several subsystems, and all the subsystems are connected by a fixed topology network, which is the definition for the packet loss among the subsystems. To better use the successfully transmitted information via Internet, both the phenomena of actuator saturation and packet loss resulting from the limitation of the communication bandwidth are taken into consideration. A novel distributed controller model is established to account for the actuator saturation and packet loss in a unified representation by using two sets of Bernoulli distributed white sequences with known conditional probabilities. With the nonlinear feedback control law represented by the convex hull of a group of linear feedback laws, the distributed controllers for subsystems are obtained by solving an linear matrix inequality (LMI) optimisation problem. Finally, numerical studies demonstrate the effectiveness of the proposed techniques.
Long working range mercury droplet actuation
This paper reports novel mercury droplet actuators with a long working range. The actuators were designed so that they can be used as thermal switches. Two types of actuation electrode were investigated: electrowetting type and electrostatic type. It was confirmed that the actuation of a mercury droplet was possible with each electrode. In addition, two types of actuator surface were investigated: flat surface and surface with micropillars. The micropillars showed considerable mobility enhancement of the droplet, but were found to be useful only with an appropriate electrode design. When the mercury droplet was actuated by 100–300 Vp-p, the observed maximum working range was about 200 µm, which is much longer than the values reported previously. Poor repeatability of droplet motion due to the charge-up of the actuator surface was revealed as a problem
Hydraulic involute cam actuator
Love, Lonnie J.; Lind, Randall F.
2011-11-01
Mechanical joints are provided in which the angle between a first coupled member and a second coupled member may be varied by mechanical actuators. In some embodiments the angle may be varied around a pivot axis in one plane and in some embodiments the angle may be varied around two pivot axes in two orthogonal planes. The joints typically utilize a cam assembly having two lobes with an involute surface. Actuators are configured to push against the lobes to vary the rotation angle between the first and second coupled member.
Quang Truong, Dinh; Ahn, Kyoung Kwan
2014-07-01
An ion polymer metal composite (IPMC) is an electroactive polymer that bends in response to a small applied electric field as a result of mobility of cations in the polymer network and vice versa. This paper presents an innovative and accurate nonlinear black-box model (NBBM) for estimating the bending behavior of IPMC actuators. The model is constructed via a general multilayer perceptron neural network (GMLPNN) integrated with a smart learning mechanism (SLM) that is based on an extended Kalman filter with self-decoupling ability (SDEKF). Here the GMLPNN is built with an ability to autoadjust its structure based on its characteristic vector. Furthermore, by using the SLM based on the SDEKF, the GMLPNN parameters are optimized with small computational effort, and the modeling accuracy is improved. An apparatus employing an IPMC actuator is first set up to investigate the IPMC characteristics and to generate the data for training and validating the model. The advanced NBBM model for the IPMC system is then created with the proper inputs to estimate IPMC tip displacement. Next, the model is optimized using the SLM mechanism with the training data. Finally, the optimized NBBM model is verified with the validating data. A comparison between this model and the previously developed model is also carried out to prove the effectiveness of the proposed modeling technique.
An ion polymer metal composite (IPMC) is an electroactive polymer that bends in response to a small applied electric field as a result of mobility of cations in the polymer network and vice versa. This paper presents an innovative and accurate nonlinear black-box model (NBBM) for estimating the bending behavior of IPMC actuators. The model is constructed via a general multilayer perceptron neural network (GMLPNN) integrated with a smart learning mechanism (SLM) that is based on an extended Kalman filter with self-decoupling ability (SDEKF). Here the GMLPNN is built with an ability to autoadjust its structure based on its characteristic vector. Furthermore, by using the SLM based on the SDEKF, the GMLPNN parameters are optimized with small computational effort, and the modeling accuracy is improved. An apparatus employing an IPMC actuator is first set up to investigate the IPMC characteristics and to generate the data for training and validating the model. The advanced NBBM model for the IPMC system is then created with the proper inputs to estimate IPMC tip displacement. Next, the model is optimized using the SLM mechanism with the training data. Finally, the optimized NBBM model is verified with the validating data. A comparison between this model and the previously developed model is also carried out to prove the effectiveness of the proposed modeling technique. (paper)
A novel spherical actuator: Design and control
Wang, J B; Jewell, G. W.; Howe, D
1997-01-01
The paper describes the design and control of a novel spherical permanent magnet actuator which is capable of two-degrees-freedom and a high specific torque. Based on an analytical actuator model, an optimal design procedure is developed to yield maximum output torque or maximum system acceleration for a given payload. The control of the actuator, whose dynamics are similar to those of robotic manipulators, is facilitated by the establishment of a complete actuation system model. A robust con...
Electrochemomechanical constrained multiobjective optimization of PPy/MWCNT actuators
Polypyrrole (PPy) conducting polymers have shown a great potential for the fabrication of conjugated polymer-based actuating devices. Consequently, they have been a key point in developing many advanced emerging applications such as biomedical devices and biomimetic robotics. When designing an actuator, taking all of the related decision variables, their roles and relationships into consideration is of pivotal importance to determine the actuator’s final performance. Therefore, the central focus of this study is to develop an electrochemomechanical constrained multiobjective optimization model of a PPy/MWCNTs trilayer actuator. For this purpose, the objective functions are designed to capture the three main characteristics of these actuators, namely their tip vertical displacement, blocking force and response time. To obtain the optimum range of the designated decision variables within the feasible domain, a multiobjective optimization algorithm is applied while appropriate constraints are imposed. The optimum points form a Pareto surface on which they are consistently spread. The numerical results are presented; these results enable one to design an actuator with consideration to the desired output performances. For the experimental analysis, a multilayer bending-type actuator is fabricated, which is composed of a PVDF layer and two layers of PPy with an incorporated layer of multi-walled carbon nanotubes deposited on each side of the PVDF membrane. The numerical results are experimentally verified; in order to determine the performance of the fabricated actuator, its outputs are compared with a neat PPy actuator’s experimental and numerical counterparts. (paper)
Mirror-scanning mechanisms are a key component in optical systems for diverse applications. However, the applications of existing piezoelectric scanners are limited due to their small angular travels. To overcome this problem, a novel two-axis mirror-scanning mechanism, which consists of a two-axis tip-tilt flexure mechanism and a set of piezoelectric actuators, is proposed in this paper. The focus of this research is on the design, theoretical modeling, and optimization of the piezoelectric-driven mechanism, with the goal of achieving large angular travels in a compact size. The design of the two-axis tip-tilt flexure mechanism is based on two nonuniform beams, which translate the limited linear output displacements of the piezoelectric actuators into large output angles. To exactly predict the angular travels, we built a voltage-angle model that characterizes the relationship between the input voltages to the piezoelectric actuators and the output angles of the piezoelectric-driven mechanism. Using this analytical model, the optimization is performed to improve the angular travels. A prototype of the mirror-scanning mechanism is fabricated based on the optimization results, and experiments are implemented to test the two-axis output angles. The experimental result shows that the angular travels of the scanner achieve more than 50 mrad, and the error between the analytical model and the experiment is about 11%. This error is much smaller than the error for the model built using the previous method because the influence of the stiffness of the mechanical structure on the deformation of the piezoelectric stack is considered in the voltage-angle model. (paper)
Vranish, John
2009-01-01
T-slide linear actuators use gear bearing differential epicyclical transmissions (GBDETs) to directly drive a linear rack, which, in turn, performs the actuation. Conventional systems use a rotary power source in conjunction with a nut and screw to provide linear motion. Non-back-drive properties of GBDETs make the new actuator more direct and simpler. Versions of this approach will serve as a long-stroke, ultra-precision, position actuator for NASA science instruments, and as a rugged, linear actuator for NASA deployment duties. The T slide can operate effectively in the presence of side forces and torques. Versions of the actuator can perform ultra-precision positioning. A basic T-slide actuator is a long-stroke, rack-and-pinion linear actuator that, typically, consists of a T-slide, several idlers, a transmission to drive the slide (powered by an electric motor) and a housing that holds the entire assembly. The actuator is driven by gear action on its top surface, and is guided and constrained by gear-bearing idlers on its other two parallel surfaces. The geometry, implemented with gear-bearing technology, is particularly effective. An electronic motor operating through a GBDET can directly drive the T slide against large loads, as a rack and pinion linear actuator, with no break and no danger of back driving. The actuator drives the slide into position and stops. The slide holes position with power off and no brake, regardless of load. With the T slide configuration, this GBDET has an entire T-gear surface on which to operate. The GB idlers coupling the other two T slide parallel surfaces to their housing counterpart surfaces provide constraints in five degrees-of-freedom and rolling friction in the direction of actuation. Multiple GB idlers provide roller bearing strength sufficient to support efficient, rolling friction movement, even in the presence of large, resisting forces. T-slide actuators can be controlled using the combination of an off
Dielectric barrier discharge plasma actuator for flow control
Opaits, Dmitry Florievich
Electrohydrodynamic (EHD) and magnetohydrodynamic phenomena are being widely studied for aerodynamic applications. The major effects of these phenomena are heating of the gas, body force generation, and enthalpy addition or extraction, [1, 2, 3]. In particular, asymmetric dielectric barrier discharge (DBD) plasma actuators are known to be effective EHD device in aerodynamic control, [4, 5]. Experiments have demonstrated their effectiveness in separation control, acoustic noise reduction, and other aeronautic applications. In contrast to conventional DBD actuators driven by sinusoidal voltages, we proposed and used a voltage profile consisting of nanosecond pulses superimposed on dc bias voltage. This produces what is essentially a non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The advantage of this non-self-sustained discharge is that the parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. Experimental studies were conducted of a flow induced in a quiescent room air by a single DBD actuator. A new approach for non-intrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low
Hydrological land surface modelling
Ridler, Marc-Etienne Francois
and disaster management. The objective of this study is to develop and investigate methods to reduce hydrological model uncertainty by using supplementary data sources. The data is used either for model calibration or for model updating using data assimilation. Satellite estimates of soil moisture and...
Modeling and control of actuators and co-surge in turbocharged engines
Thomasson, Andreas
2014-01-01
The torque response of the engine is important for the driving experience of a vehicle. In spark ignited engines, torque is proportional to the air flow into the cylinders. Controlling torque therefore implies controlling air flow. In modern turbocharged engines, the driver commands are interpreted by an electronic control unit that controls the engine through electromechanical and pneumatic actuators. Air flow to the intake manifold is controlled by an electronic throttle, and a wastegate co...
Distributed structural control using multilayered piezoelectric actuators
Cudney, Harley H.; Inman, Daniel J.; Oshman, Yaakov
1990-01-01
A method of segmenting piezoelectric sensors and actuators is proposed which can preclude the currently experienced cancelation of sensor signals, or the reduction of actuator effectiveness, due to the integration of the property undergoing measurement or control. The segmentation method is demonstrated by a model developed for beam structures, to which multiple layers of piezoelectric materials are attached. A numerical study is undertaken of increasing active and passive damping of a beam using the segmented sensors and actuators over unsegmented sensors and actuators.
This paper describes ORNL's development of an environment for the simulation of robotic manipulators. Simulation includes the modeling of kinematics, dynamics, sensors, actuators, control systems, operators, and environments. Models will be used for manipulator design, proposal evaluation, control system design and analysis, graphical preview of proposed motions, safety system development, and training. Of particular interest is the development of models for robotic manipulators having at least one flexible link. As a first application, models have been developed for the Pacific Northwest Laboratory's Flexible Beam Test Bed (PNL FBTB), which is a 1-Degree-of-Freedom, flexible arm with a hydraulic base actuator. ORNL transferred control algorithms developed for the PNL FBTB to controlling IGRIP models. A robust notch filter is running in IGRIP controlling a full dynamics model of the PNL test bed. Model results provide a reasonable match to the experimental results (quantitative results are being determined) and can run on ORNL's Onyx machine in approximately realtime. The flexible beam is modeled as six rigid sections with torsional springs between each segment. The spring constants were adjusted to match the physical response of the flexible beam model to the experimental results. The controller is able to improve performance on the model similar to the improvement seen on the experimental system. Some differences are apparent, most notably because the IGRIP model presently uses a different trajectory planner than the one used by ORNL on the PNL test bed. In the future, the trajectory planner will be modified so that the experiments and models are the same. The successful completion of this work provides the ability to link C code with IGRIP, thus allowing controllers to be developed, tested, and tuned in simulation and then ported directly to hardware systems using the C language
Surface dielectric barrier discharges have been proposed as means of airflow actuation. A simplified air plasma model fully coupled with gas dynamics is presented and solved numerically using asynchronous mesh adaptation and time integration. Two modes of actuation depending on the driving voltage waveform are presented and analyzed. The first one uses high-voltage sine waveform in the kilohertz frequency range to transfer momentum from ions to gas molecules. The second one uses high-voltage nanosecond pulses to transfer energy to the neutral gas on a short time scale thus generating shockwaves.
Unfer, T; Boeuf, J-P, E-mail: unfer@laplace.univ-tlse.f [Universite de Toulouse, UPS, INPT, LAPLACE, Toulouse (France)
2010-12-15
Surface dielectric barrier discharges have been proposed as means of airflow actuation. A simplified air plasma model fully coupled with gas dynamics is presented and solved numerically using asynchronous mesh adaptation and time integration. Two modes of actuation depending on the driving voltage waveform are presented and analyzed. The first one uses high-voltage sine waveform in the kilohertz frequency range to transfer momentum from ions to gas molecules. The second one uses high-voltage nanosecond pulses to transfer energy to the neutral gas on a short time scale thus generating shockwaves.
Modelling land surface - atmosphere interactions
Rasmussen, Søren Højmark
The study is investigates modelling of land surface – atmosphere interactions in context of fully coupled climatehydrological model. With a special focus of under what condition a fully coupled model system is needed. Regional climate model inter-comparison projects as ENSEMBLES have shown bias...
The k-ε-f_{P} model applied to double wind turbine wakes using different actuator disk force methods
Laan, van der, Paul Maarten; Sørensen, Niels N.; Réthoré, Pierre-Elouan; Mann, Jakob; Kelly, Mark C.; Troldborg, Niels
2015-01-01
The newly developed k-ε-fP eddy viscosity model is applied to double wind turbine wake configurations in a neutral atmospheric boundary layer, using a Reynolds-Averaged Navier–Stokes solver. The wind turbines are represented by actuator disks. A proposed variable actuator disk force method is...... two methods overpredict it. The results of the k-ε-fP eddy viscosity model are also compared with the original k-ε eddy viscosity model and large-eddy simulations. Compared to the large-eddy simulations-predicted velocity and power deficits, the k-ε-fP is superior to the original k-ε model...
Kumar, Parikshith K.; Desai, Uri; Chatzigeorgiou, George; Lagoudas, Dimitris C.; Monroe, James; Karaman, Ibrahim; Noebe, Ron; Bigelow, Glen
2010-01-01
The present work is focused on studying the cycling actuation behavior of HTSMAs undergoing simultaneous creep and transformation. For the thermomechanical testing, a high temperature test setup was assembled on a MTS frame with the capability to test up to temperatures of 600 C. Constant stress thermal cycling tests were conducted to establish the actuation characteristics and the phase diagram for the chosen HTSMA. Additionally, creep tests were conducted at constant stress levels at different test temperatures to characterize the creep behavior of the alloy over the operational range. A thermodynamic constitutive model is developed and extended to take into account a) the effect of multiple thermal cycling on the generation of plastic strains due to transformation (TRIP strains) and b) both primary and secondary creep effects. The model calibration is based on the test results. The creep tests and the uniaxial tests are used to identify the viscoplastic behavior of the material. The parameters for the SMA properties, regarding the transformation and transformation induced plastic strain evolutions, are obtained from the material phase diagram and the thermomechanical tests. The model is validated by predicting the material behavior at different thermomechanical test conditions.
Modular droplet actuator drive
Pollack, Michael G. (Inventor); Paik, Philip (Inventor)
2011-01-01
A droplet actuator drive including a detection apparatus for sensing a property of a droplet on a droplet actuator; circuitry for controlling the detection apparatus electronically coupled to the detection apparatus; a droplet actuator cartridge connector arranged so that when a droplet actuator cartridge electronically is coupled thereto: the droplet actuator cartridge is aligned with the detection apparatus; and the detection apparatus can sense the property of the droplet on a droplet actuator; circuitry for controlling a droplet actuator coupled to the droplet actuator connector; and the droplet actuator circuitry may be coupled to a processor.
Smart Tendon Actuated Flexible Actuator
Md. Masum Billah; Raisuddin Khan
2015-01-01
We investigate the kinematic feasibility of a tendon-based flexible parallel platform actuator. Much of the research on tendon-driven Stewart platforms is devoted either to the completely restrained positioning mechanism (CRPM) or to one particular type of the incompletely restrained positioning mechanism (IRPM) where the external force is provided by the gravitational pull on the platform such as in cable-suspended Stewart platforms. An IRPM-based platform is proposed which uses the external...
Wang, Yanjie; Zhu, Zicai; Liu, Jiayu; Chang, Longfei; Chen, Hualing
2016-08-01
In this paper, the surface of a Nafion membrane was roughened by the sandblasting method, mainly considering the change of sandblasting time and powder size. The roughened surfaces were characterized in terms of their topography from the confocal laser scanning microscope (CLSM) and SEM. The key surface parameters, such as Sa (the arithmetical mean deviation of the specified surface profile), SSA (the surface area ratio before and after roughening) and the area measurement on the histogram from the CLSM images, were extracted and evaluated from the roughened membranes. Also, the detailed change in surface and interfacial electrodes were measured and discussed together with the surface resistance, equivalent modulus, capacitance and performances of IPMC actuators based on the roughened membranes. The results show that a suitable sandblasting condition, resulting in the decrease in the bending stiffness and the increase in the interface area closely related to the capacitance, can effectively increase the electromechanical responses of IPMCs. Although the surface roughening by sandblasting caused a considerable lowering of mechanical strength, it was very effective for enlarging the interfacial area between Nafion membrane and the electrode layers, and for forming a penetrated electrode structure, which facilitated improvement of the surface resistance and capacitance characteristics of IPMCs. In this work, a quantitative relationship was built between the topography of Nafion membrane surface and electromechanical performance of IPMCs by means of sandblasting.
Linear stability analysis for an optimum Glauert rotor modelled by an actuator disc
We approximate a wind turbine using the Actuator Disc methodology with loading for an optimum Glauert rotor, and vary blade length and tip speed ratio, to determine base flows for linear stability computations at a Reynolds number of 100. Results from such computations suggest that the least stable mode is axisymmetric and insensitive to changes in tip speed operation, suggesting that the stability properties in the farfield wake for an optimised rotor are independent of the chosen tip speed optimization point. Higher azimuthal modes promote greater variation in velocities and may be relevant to cases at higher Reynolds numbers
Computer Modeling and Optimization of DC Actuators with a System of Permanent Magnets
Ulrych, B.; Karban, P.; Doležel, Ivo
Madeira : APDEE, 2007, s. 1-6. ISBN 978-972-8822-09-5. [ Portuguese -Spanish Congress in Electrical Engineering - XCLEEE /10./. Madeira - Funchal (PT), 05.07.2007-08.07.2007] R&D Projects: GA ČR GA102/04/0095; GA AV ČR IAA100760702 Institutional research plan: CEZ:AV0Z20570509 Keywords : electromagnetic actuator * permanent magnet * magnetic field Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering http://www.apdee.org/index.php?pageid=1117
Accurate control systems are critical for safe and practical utilization of microrobots for in vivo operations. There exist uncertainties from the microrobot dynamics and nonlinearities from the magnetic driving force in the electromagnetic in vivo manipulation of microrobots, especially in low Reynolds number fluid flow. We describe the modeling and implementation of a closed-loop control system for a magnetically actuated microrobot based on time-delay estimation (TDE). The microrobot consisted of a cylindrical magnet, 0.5 mm in diameter and 1 mm in length, and the controller used optical sensing for position feedback. In addition, we describe an analytical model to determine the magnetic field components and the field gradients of a custom set of coils used to actuate the microrobot. Simulations were carried out to investigate the properties of the TDE control system, and it was subsequently tested experimentally, demonstrating that it provides robust control of the microrobot trajectory and does not exhibit chattering to follow step inputs. (paper)
Pavement Aging Model by Response Surface Modeling
Manzano-Ramírez A.
2011-10-01
Full Text Available In this work, surface course aging was modeled by Response Surface Methodology (RSM. The Marshall specimens were placed in a conventional oven for time and temperature conditions established on the basis of the environment factors of the region where the surface course is constructed by AC-20 from the Ing. Antonio M. Amor refinery. Volatilized material (VM, load resistance increment (ΔL and flow resistance increment (ΔF models were developed by the RSM. Cylindrical specimens with real aging were extracted from the surface course pilot to evaluate the error of the models. The VM model was adequate, in contrast (ΔL and (ΔF models were almost adequate with an error of 20 %, that was associated with the other environmental factors, which were not considered at the beginning of the research.
Micro-actuation characteristics of rocket conical shell sections
Chai, W. K.; Han, Y.; Higuchi, K.; Tzou, H. S.
2006-05-01
Rocket fairings, load-carrying structures of solid rocket motor case, e.g., inter-stage joint, satellite-rocket joint, etc., usually take the shape of conical shell sections. This paper is to evaluate spatially distributed microscopic control characteristics of distributed actuator patches bonded on conical shell surfaces. The converse effect of piezoelectric materials has been recognized as one of the best electromechanical effects for precision distributed control applications. The resultant control forces and micro-control actions induced by the distributed actuators depend on applied voltages, geometrical (e.g., spatial segmentation and shape) and material (i.e., various actuator materials) properties. Mathematical models and modal domain governing equations of the conical shell section laminated with distributed actuator patches are presented first, followed by formulations of distributed control forces and micro-control actions which can be divided into longitudinal/circumferential membrane and bending control components. Spatially distributed electromechanical microscopic actuation characteristics and control effects resulting from various longitudinal/circumferential actions of actuator patches are evaluated.
Mangina, R. S.; Enloe, C. L.; Font, G. I.
2015-11-01
We present an experimental case study of time-resolved force production by an aerodynamic plasma actuator immersed in various mixtures of electropositive (N2) and electronegative gases (O2 and SF6) at atmospheric pressure using a fixed AC high-voltage input of 16 kV peak amplitude at 200 Hz frequency. We have observed distinct changes in the discharge structures during both negative- and positive-going voltage half-cycles, with corresponding variations in the actuator's force production: a ratio of 4:1 in the impulse produced by the negative-going half-cycle of the discharge among the various gas mixtures we explored, 2:1 in the impulse produced by the positive-going half-cycle, and cases in which the negative-going half-cycle dominates force production (by a ratio of 1.5:1), where the half-cycles produce identical force levels, and where the positive-going half cycle dominates (by a ratio of 1:5). We also present time-resolved experimental evidence for the first time that shows electrons do play a significant role in the momentum coupling to surrounding neutrals during the negative going voltage half-cycle of the N2 discharge. We show that there is sufficient macroscopic variation in the plasma that the predictions of numerical models at the microscopic level can be validated even though the plasma itself cannot be measured directly on those spatial and temporal scales.
XU, F.
2013-05-01
Full Text Available Orbital Friction Vibration Actuator (OFVA is a core component of Orbital Friction Welding (OFW, which is a novel apertureless welding technology utilizing friction heat to implement solid-state joining. In this paper, topology and operational principle of OFVA are introduced, the analytical formulas of the electromagnetic force for the x and y directions, which can drive the mover to generate a circular motion trajectory, are derived, and the characteristic of static electromagnetic force is predicted by analytical method and 2-D (two-dimensional FEM (finite element method, 3-D and measurement. The coupled magnetic field-circuit-motion simulation models which are driven by current and voltage source are established, respectively, and some of its operational characteristics are analyzed. Simulation and experiment validate theoretical analysis and the feasibility of the fabricated prototype, demonstrate the good performance of the OFVA, and provide valuable reference for engineering applications.
Shunsuke Nansai
2015-01-01
Full Text Available The Theo Jansen mechanism is gaining widespread popularity among the legged robotics community due to its scalable design, energy efficiency, low payload-to-machine-load ratio, bioinspired locomotion, and deterministic foot trajectory. In this paper, we perform for the first time the dynamic modeling and analysis on a four-legged robot driven by a single actuator and composed of Theo Jansen mechanisms. The projection method is applied to derive the equations of motion of this complex mechanical system and a position control strategy based on energy is proposed. Numerical simulations validate the efficacy of the designed controller, thus setting a theoretical basis for further investigations on Theo Jansen based quadruped robots.
Performance Enhancement of a Vertical Tail Model with Sweeping Jet Actuators
Seele, Roman; Graff, Emilio; Lin, John; Wygnanski, Israel
2013-01-01
Active Flow Control (AFC) experiments performed at the Caltech Lucas Adaptive Wall Wind Tunnel on a 12%-thick, generic vertical tail model indicated that sweeping jets emanating from the trailing edge (TE) of the vertical stabilizer significantly increased the side force coefficient for a wide range of rudder deflection angles and yaw angles at free-stream velocities approaching takeoff rotation speed. The results indicated that 2% blowing momentum coefficient (C(sub mu) increased the side force in excess of 50% at the maximum conventional rudder deflection angle in the absence of yaw. Even C(sub mu) = 0.5% increased the side force in excess of 20% under these conditions. This effort was sponsored by the NASA Environmentally Responsible Aviation (ERA) project and the successful demonstration of this flow-control application could have far reaching implications. It could lead to effective applications of AFC technologies on key aircraft control surfaces and lift enhancing devices (flaps) that would aid in reduction of fuel consumption through a decrease in size and weight of wings and control surfaces or a reduction of the noise footprint due to steeper climb and descent.
Soft Pneumatic Actuators for Rehabilitation
Guido Belforte
2014-05-01
Full Text Available Pneumatic artificial muscles are pneumatic devices with practical and various applications as common actuators. They, as human muscles, work in agonistic-antagonistic way, giving a traction force only when supplied by compressed air. The state of the art of soft pneumatic actuators is here analyzed: different models of pneumatic muscles are considered and evolution lines are presented. Then, the use of Pneumatic Muscles (PAM in rehabilitation apparatus is described and the general characteristics required in different applications are considered, analyzing the use of proper soft actuators with various technical properties. Therefore, research activity carried out in the Department of Mechanical and Aerospace Engineering in the field of soft and textile actuators is presented here. In particular, pneumatic textile muscles useful for active suits design are described. These components are made of a tubular structure, with an inner layer of latex coated with a deformable outer fabric sewn along the edge. In order to increase pneumatic muscles forces and contractions Braided Pneumatic Muscles are studied. In this paper, new prototypes are presented, based on a fabric construction and various kinds of geometry. Pressure-force-deformation tests results are carried out and analyzed. These actuators are useful for rehabilitation applications. In order to reproduce the whole upper limb movements, new kind of soft actuators are studied, based on the same principle of planar membranes deformation. As an example, the bellows muscle model and worm muscle model are developed and described. In both cases, wide deformations are expected. Another issue for soft actuators is the pressure therapy. Some textile sleeve prototypes developed for massage therapy on patients suffering of lymph edema are analyzed. Different types of fabric and assembly techniques have been tested. In general, these Pressure Soft Actuators are useful for upper/lower limbs treatments
Bluff Body Flow Control Using Plasma Actuators
Thomas, Flint
2005-11-01
In this study, the use of single dielectric barrier discharge plasma actuators for the control of bluff body flow separation is investigated. In particular, surface mounted plasma actuators are used to reduce both drag and unsteady vortex shedding from circular cylinders in cross-flow. It is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. Large reductions in vortex shedding and drag are demonstrated for Reynolds numbers ˜ 10^410^5. Both steady and unsteady plasma-induced surface blowing is explored. Results are presented from experiments involving both two and four surface mounted actuators.
We present an experimental case study of time-resolved force production by an aerodynamic plasma actuator immersed in various mixtures of electropositive (N2) and electronegative gases (O2 and SF6) at atmospheric pressure using a fixed AC high-voltage input of 16 kV peak amplitude at 200 Hz frequency. We have observed distinct changes in the discharge structures during both negative- and positive-going voltage half-cycles, with corresponding variations in the actuator's force production: a ratio of 4:1 in the impulse produced by the negative-going half-cycle of the discharge among the various gas mixtures we explored, 2:1 in the impulse produced by the positive-going half-cycle, and cases in which the negative-going half-cycle dominates force production (by a ratio of 1.5:1), where the half-cycles produce identical force levels, and where the positive-going half cycle dominates (by a ratio of 1:5). We also present time-resolved experimental evidence for the first time that shows electrons do play a significant role in the momentum coupling to surrounding neutrals during the negative going voltage half-cycle of the N2 discharge. We show that there is sufficient macroscopic variation in the plasma that the predictions of numerical models at the microscopic level can be validated even though the plasma itself cannot be measured directly on those spatial and temporal scales
Kuang, Y; Hilgers, A; Sadiq, M; Cochran, S; Corner, G; Huang, Z
2016-07-01
Clear needle visualisation is recognised as an unmet need for ultrasound guided percutaneous needle procedures including regional anaesthesia and tissue biopsy. With inadequate needle visibility, these procedures may result in serious complications or a failed operation. This paper reports analysis of the modal behaviour of a previously proposed ultrasound-actuated needle configuration, which may overcome this problem by improving needle visibility in colour Doppler imaging. It uses a piezoelectric transducer to actuate longitudinal resonant modes in needles (outer diameter 0.8-1.2mm, length>65mm). The factors that affect the needle's vibration mode are identified, including the needle length, the transducer's resonance frequency and the gripping position. Their effects are investigated using finite element modelling, with the conclusions validated experimentally. The actuated needle was inserted into porcine tissue up to 30mm depth and its visibility was observed under colour Doppler imaging. The piezoelectric transducer is able to generate longitudinal vibration with peak-to-peak amplitude up to 4μm at the needle tip with an actuating voltage of 20Vpp. Actuated in longitudinal vibration modes (distal mode at 27.6kHz and transducer mode at 42.2kHz) with a drive amplitude of 12-14Vpp, a 120mm needle is delineated as a coloured line in colour Doppler images, with both needle tip and shaft visualised. The improved needle visibility is maintained while the needle is advanced into the tissue, thus allowing tracking of the needle position in real time. Moreover, the needle tip is highlighted by strong coloured artefacts around the actuated needle generated by its flexural vibration. A limitation of the technique is that the transducer mode requires needles of specific lengths so that the needle's resonance frequency matches the transducer. This may restrict the choice of needle lengths in clinical applications. PMID:27022669
A Foldable Antagonistic Actuator
Shintake, Jun; Rosset, Samuel; Schubert, Bryan Edward; Floreano, Dario; Shea, Herbert
2015-01-01
We report on an actuator based on dielectric elastomers that is capable of antagonistic actuation and passive folding. This actuator enables foldability in robots with simple structures. Unlike other antagonistic dielectric elastomer devices, our concept uses elastic hinges to allow the folding of the structure, which also provides an additional design parameter. To validate the actuator concept through a specific application test, a foldable elevon actuator with outline size of 70 mm × 130 m...
Highlights: • A Real Time Model of a turbine bypass system is presented and validated. • An Hardware in the Loop rig is used for calibration of positioneers and turbine bypass regulators. • Testing activities on the proposed test rig, confirm the feasibility of the proposed approach. - Abstract: During the start-up and shut-down phases of steam power plants many components are subjected to pressure and temperature transients that have to be carefully regulated both for safety and reliability reasons. For this reason, there is a growing interest in the optimization of turbine bypass controllers and actuators which are mainly used to regulate the plant during this kind of operations. In this work, a numerically efficient model for Real Time (RT) simulation of a steam plant is presented. In particular, a modular Simulink™ library of components such as valves, turbines and heaters has been developed. In this way it is possible to easily assemble and customize models able to simulate different plants and operating scenarios. The code, which is implemented for a fixed, discrete step solver, can be easily compiled for a RT target (such as a Texas Instrument DSP) in order to be executed in Real Time on a low cost industrial hardware. The proposed model has been used for quite innovative applications such as the development of a Hardware In the Loop (HIL) test rig of turbine bypass controllers and valve positioners. Preliminary experimental activities and results of the proposed test rig developed for Velan ABV are introduced and discussed
Transputer Control of Hydraulic Actuators and Robots
Conrad, Finn
1996-01-01
Results from a Danish mechatronics research program entitled IMCIA - Intelligent Control and Intelligent Actuators. The objective is development of intelligent actuators for intelligent motion control. A mechatronics test facility with a transputer controlled hydraulic robot suiteable for real......-time experiments and evaluation of control laws and algorithms is presented. Concepts of intelligent motion control and intelligent hydraulic actuators are proposed. Promising experimental path-tracking results obtained from model-based adaptive control algorithms are presented and discussed....
Smart Tendon Actuated Flexible Actuator
Md. Masum Billah
2015-01-01
Full Text Available We investigate the kinematic feasibility of a tendon-based flexible parallel platform actuator. Much of the research on tendon-driven Stewart platforms is devoted either to the completely restrained positioning mechanism (CRPM or to one particular type of the incompletely restrained positioning mechanism (IRPM where the external force is provided by the gravitational pull on the platform such as in cable-suspended Stewart platforms. An IRPM-based platform is proposed which uses the external force provided by a compliant member. The compliant central column allows the configuration to achieve n DOFs with n tendons. In particular, this investigation focuses on the angular deflection of the upper platform with respect to the lower platform. The application here is aimed at developing a linkable module that can be connected to one another so as to form a “snake robot” of sorts. Since locomotion takes precedence over positioning in this application, a 3-DOF Stewart platform is adopted. For an arbitrary angular displace of the end-effector, the corresponding length of each tendon can be determined through inverse kinematics. Mathematical singularities are investigated using the traditional analytical method of defining the Jacobian.
MacMillan, P.N.
1985-06-01
Recent improvements in rare earth magnets have made it possible to construct strong, lightweight, high-horsepower DC motors. This has occasioned a reassessment of electromechanical actuators as alternatives to comparable pneumatic and hydraulic systems for use as flight-control actuators for tactical missiles. A dynamic equivalent circuit model for the analysis of a small four pole brushless DC motor fed by a transistorized power conditioner utilizing high speed switching power transistors as final elements is presented. The influence of electronic commutation on instantaneous dynamic motor performance is particularly demonstrated and good correlation between computer simulation and typical experimentally obtained performance data is achieved. The model is implemented in CSMP language and features more accurate air gap flux representation over previous work. Hall-effect sensor rotor position feedback is simulated. Both constant and variable-air-gap flux is modeled and the variable flux model treats the flux as a fundamental and one harmonic.
Repulsive-force out-of-plane large stroke translation micro electrostatic actuator
A repulsive-force out-of-plane large stroke translation micro electrostatic actuator is presented. A model of the actuator is presented and is used to relate the applied voltage to the out-of-plane displacement. Prototypes of the actuator are fabricated using the surface micromachining technology PolyMUMPs. The measured results show that the actuator can achieve a static out-of-plane translation of 86 µm for a driving voltage of 200 V. The measured static performance matches well with the results predicted by the model. The measured bandwidth (–3 dB) for the out-of-plane translation of the micro actuator is 80 and 200 Hz for input sinusoidal driving voltages varying in the ranges of 75–125 V and 125–175 V, respectively. The translation micro actuator can also achieve 2D rotation along any direction within a mechanical rotation range of ±1.5°. Vector display based on the actuator is also demonstrated
Marjanovic, N.; Mirocha, J. D.; Chow, F. K.
2013-12-01
In this work, we examine the performance of a generalized actuator disk (GAD) model embedded within the Weather Research and Forecasting (WRF) atmospheric model to study wake effects on successive rows of turbines at a North American wind farm. These wake effects are of interest as they can drastically reduce down-wind energy extraction and increase turbulence intensity. The GAD, which is designed for turbulence-resolving simulations, is used within downscaled large-eddy simulations (LES) forced with mesoscale simulations and WRF's grid nesting capability. The GAD represents the effects of thrust and torque created by a wind turbine on the atmosphere within a disk representing the rotor swept area. The lift and drag forces acting on the turbine blades are parameterized using blade-element theory and the aerodynamic properties of the blades. Our implementation permits simulation of turbine wake effects and turbine/airflow interactions within a realistic atmospheric boundary layer flow field, including resolved turbulence, time-evolving mesoscale forcing, and real topography. The GAD includes real-time yaw and pitch control to respond realistically to changing flow conditions. Simulation results are compared to SODAR data from operating wind turbines and an already existing WRF mesoscale turbine drag parameterization to validate the GAD parameterization.
Zhou, Miaolei; Zhang, Qi; Wang, Jingyuan
2014-01-01
As a new type of smart material, magnetic shape memory alloy has the advantages of a fast response frequency and outstanding strain capability in the field of microdrive and microposition actuators. The hysteresis nonlinearity in magnetic shape memory alloy actuators, however, limits system performance and further application. Here we propose a feedforward-feedback hybrid control method to improve control precision and mitigate the effects of the hysteresis nonlinearity of magnetic shape memo...
Shape-Memory-Alloy Actuator For Flight Controls
Barret, Chris
1995-01-01
Report proposes use of shape-memory-alloy actuators, instead of hydraulic actuators, for aerodynamic flight-control surfaces. Actuator made of shape-memory alloy converts thermal energy into mechanical work by changing shape as it makes transitions between martensitic and austenitic crystalline phase states of alloy. Because both hot exhaust gases and cryogenic propellant liquids available aboard launch rockets, shape-memory-alloy actuators exceptionally suited for use aboard such rockets.
Nonlinear analysis of RAINBOW actuator characteristics
This paper discusses an investigation into deformations of rectangular RAINBOW actuators, which are classified as a type of laminated actuator. The actuators consist of a piezoelectric active layer and a reduced passive layer formed in an elevated temperature reduction process. An energy-based Rayleigh–Ritz model is used to approximate the thermally induced deformations with 23-term polynomials. Due to large out-of-plane displacements of the RAINBOW actuators after cooling down to room temperature, inclusion of geometric nonlinearities in the kinematic relations is taken into consideration. Actuation characteristics of these actuators caused by a quasi-static electric field applied to the piezoelectric layer are also modeled with the Rayleigh–Ritz approach. Material nonlinearities in the piezoelectric layer are included in the constitutive equation to capture the effects of a strong electric field. Piezoelectrically induced tip deflections of a series of RAINBOW cantilever actuators are calculated and compared with experiment. With the geometrical and material nonlinearities taken into account, numerical simulation reveals the computed tip deflections agree very well with the experimental data. In addition, tip blocking forces representing the load-carrying capability of the RAINBOW actuators are approximately evaluated by equating the magnitude of force-induced displacement to that of the piezoelectrically induced tip deflection. Again, good agreement between numerical results and experiment can be observed in the case of the tip blocking force. This evidently shows that the pertinent nonlinearities have very crucial effects on the responses and performances of the RAINBOW actuators
Simulation of a MW rotor equipped with vortex generators using CFD and an actuator shape model
Troldborg, Niels; Zahle, Frederik; Sørensen, Niels N.
2015-01-01
This article presents a comparison of CFD simulations of the DTU 10 MW reference wind turbine with and without vortex generators installed on the inboard part of the blades. The vortex generators are modelled by introducing body forces determined using a modified version of the so-called BAY model....... The vortex generator model is validated by applying it for modelling an array of VGs on an airfoil section compared to both wind tunnel measurements and fully gridded CFD....
Experimental investigation of resonant MEMS switch with ac actuation
Pal, Jitendra; Zhu, Yong; Wang, Boyi; Lu, Junwei; Khan, Fahimullah; Viet Dao, Dzung; Wang, Yifan
2016-06-01
In this letter, modeling, analysis, and experimental investigation for a resonant MEMS switch are presented. The resonant switch harnesses its mechanical resonance to lower the required actuation voltage by a substantial factor over the switch with static actuation. With alternating actuation voltage at its mechanical resonance frequency of 6.6 kHz, the average capacitance is tuned by changing the gap between fixed and movable electrodes. Based on the proposed actuation method, the device offers 57.44% lower actuation voltage compared with the switch with static actuation.
Piezocomposite Actuator Arrays for Correcting and Controlling Wavefront Error in Reflectors
Bradford, Samuel Case; Peterson, Lee D.; Ohara, Catherine M.; Shi, Fang; Agnes, Greg S.; Hoffman, Samuel M.; Wilkie, William Keats
2012-01-01
Three reflectors have been developed and tested to assess the performance of a distributed network of piezocomposite actuators for correcting thermal deformations and total wave-front error. The primary testbed article is an active composite reflector, composed of a spherically curved panel with a graphite face sheet and aluminum honeycomb core composite, and then augmented with a network of 90 distributed piezoelectric composite actuators. The piezoelectric actuator system may be used for correcting as-built residual shape errors, and for controlling low-order, thermally-induced quasi-static distortions of the panel. In this study, thermally-induced surface deformations of 1 to 5 microns were deliberately introduced onto the reflector, then measured using a speckle holography interferometer system. The reflector surface figure was subsequently corrected to a tolerance of 50 nm using the actuators embedded in the reflector's back face sheet. Two additional test articles were constructed: a borosilicate at window at 150 mm diameter with 18 actuators bonded to the back surface; and a direct metal laser sintered reflector with spherical curvature, 230 mm diameter, and 12 actuators bonded to the back surface. In the case of the glass reflector, absolute measurements were performed with an interferometer and the absolute surface was corrected. These test articles were evaluated to determine their absolute surface control capabilities, as well as to assess a multiphysics modeling effort developed under this program for the prediction of active reflector response. This paper will describe the design, construction, and testing of active reflector systems under thermal loads, and subsequent correction of surface shape via distributed peizeoelctric actuation.
Axelrod's Model with Surface Tension
Pace, Bruno
2012-01-01
In this work we propose a subtle change in Axelrod's model for the dissemination of culture. The mechanism consists of excluding non-interacting neighbours from the set of neighbours out of which an agent is drawn for potential cultural interactions. Although the alteration proposed does not alter topologically the configuration space, it yields significant qualitative changes, specifically the emergence of surface tension, driving the system in some cases to metastable states. The transient behaviour is considerably richer, and cultural regions have become stable leading to the formation of different spatio-temporal structures. A new metastable "glassy" phase emerges between the globalised phase and the polarised, multicultural phase.
Investigation of film cooling from cylindrical hole with plasma actuator on flat plate
Xiao, Yang; Dai, Sheng-ji; He, Li-ming; Jin, Tao; Zhang, Qian; Hou, Peng-hui
2015-09-01
This paper reports the Computational Fluid Dynamics modeling studies on the effect of plasma aerodynamic actuation on combustor film cooling performance. By comparing Case (i.e. film cooling hole with plasma actuator) result to Base (i.e. film cooling hole without plasma actuator) result, the mechanism of improving film cooling performance by using plasma actuator was analyzed. The results show that the Counter Rotating Vortex Pairs in Base are weakened by a new pair of vortex in Case, which is induced by the plasma-actuator-generated arc-shape-distributed electric body force. This leads to less interaction and less mixing between the main flow and the jet flow. Then it causes enhancement of the stability and the steadiness of the jet flow. Finally the average film cooling effectiveness in Case is higher than that in Base. For Case, the uniformity of temperature distribution along spanwise wall surface is improved as the actuator electrode radian increases, so does the average film cooling effectiveness. The film cooling effectiveness is higher when actuator is closer to the exit of hole.
Palacin, J.; Salleras, M.; Puig, M.; Samitier, J.; Marco, S.
2004-07-01
In this work, we approach the problem of extracting a dynamic multiport thermal compact model from thermal impedance transients of microsystems using genetic algorithms. The model takes the form of a unique RC network, using a thermal-electrical analogy. The model topology is codified in a binary chromosoma and nonlinear least squares is used for sizing their components. The compact model topology evolution is genetically controlled to obtain the RC network that minimizes the reconstruction error of the thermal impedance transients. As an example, the proposed methodology is applied to an innovative silicon microthruster and compared with random search and sequential forward selection.
Pyrotechnic actuator: a new generation of Si integrated actuator
Rossi, C.; Esteve, D.; Mingues, C.
1998-06-01
Mechanical micro actuators on silicon is playing a major role in the development of micro-systems. In this context, many structures have been performed on electrostatic, piezo electric or pneumatic actuators. However, limitations are remaining when energetic micro actuations have to be created. We propose in this paper, a new original type of actuation based on the force generated by the combustion of an explosive. It consists of a micro-machined silicon micro-heater (3 mm x 3 mm x 0.3 mm) on which a thin film of propellant (2 mm x 2 mm x 0.2 mm) is deposited. Its functioning principle is based on a hot gas emitted by the auto combustion of the propellant when its temperature reaches 300 deg C locally. In this paper, we present the results of a study (by modelling and experimental) of the ignition and combustion of a very small quantity of explosive onto a Si-micro-machined micro-heater. We conclude by presenting two examples of applications showing the promising interest of this energetic actuator: the first application is the biomedical field. The second one is today for micro-spacecraft attitude control. (authors) 9 refs.
Kristiansen, Martin; Kryger, Mille; Zhang, Zhao;
2012-01-01
A dynamic linear DNA tile actuator is expanded to three new structures of higher complexity. The original DNA actuator was constructed from a central roller strand which hybridizes with two piston strands by forming two half-crossover junctions. A linear expansion of the actuator is obtained...
Modeling the Kelvin polarization force actuation of Micro- and Nanomechanical systems
Schmid, Silvan; Hierold, C.; Boisen, Anja
2010-01-01
element method simulations are used to characterize the scheme and to evaluate a field correction factor, which results from simplifying the form of the electric field. The model has been shown to be valid for dielectrics with different permittivities. The presented model facilitates the design of...
Wang, Donny P.; Bartley-Cho, Jonathan D.; Martin, Christopher A.; Hallam, Brian J.
2001-06-01
A key objective of the Smart Wing Phase 2, Test 2 is to demonstrate high-rate actuation of hingeless control surfaces using smart material-based actuators. Actuation rates resulting in a minimum of 20 degree(s) flap deflection in 0.33 sec, producing a sweep rate of at least 60 degree(s)/sec, are desired. This sweep rate is similar to those specified for many of the existing military platforms with hinged control surfaces. The ability to deploy control surfaces without discrete hingeline would, however, enhance platform mission by reducing radar cross section and improving aerodynamic performance. Studies on numerous actuation concepts and flexible structures were executed during the early and mid phase of the program in an effort to satisfy these goals. In the first study, several actuation concepts with different transducers were modeled and analyzed. These concepts included distributed piezoelectric stack actuators with and without hydraulic amplifiers and pumps, antagonistic tendon actuation, and eccentuation. The transducers selected for the trade studies included piezoelectric ultrasonic motors, actively cooled SMA, ferromagnetic SMA, and stacks made from piezoelectric ceramic wafer, piezoelectric single crystal wafer, irradiated PVDF-TrFE film, and dielectric elastomer film. Although many of the technologies are not fully mature, they provide a glimpse of what improvements could be possible with their successful development. The studies showed that distributed polymer stacks provided the most elegant solution, but eccentuation was deemed the most realistic and lowest risk approach to attaining the program goals. A common issue to all the concepts was the structural stiffness that the actuators worked against. This was resolved in the second study by developing a flexcore- elastomeric skin trailing edge structure with eccentuation using high power ultrasonic motors. This paper describes the two studies and the final concept in detail.
Robust Quasi–LPV Model Reference FTC of a Quadrotor Uav Subject to Actuator Faults
Rotondo Damiano
2015-03-01
Full Text Available A solution for fault tolerant control (FTC of a quadrotor unmanned aerial vehicle (UAV is proposed. It relies on model reference-based control, where a reference model generates the desired trajectory. Depending on the type of reference model used for generating the reference trajectory, and on the assumptions about the availability and uncertainty of fault estimation, different error models are obtained. These error models are suitable for passive FTC, active FTC and hybrid FTC, the latter being able to merge the benefits of active and passive FTC while reducing their respective drawbacks. The controller is generated using results from the robust linear parameter varying (LPV polytopic framework, where the vector of varying parameters is used to schedule between uncertain linear time invariant (LTI systems. The design procedure relies on solving a set of linear matrix inequalities (LMIs in order to achieve regional pole placement and H∞ norm bounding constraints. Simulation results are used to compare the different FTC strategies.
Reliable Actuation in Sensor Networks
Sean Rooney
2007-12-01
Full Text Available We present a protocol that uses a publish/subscribe approach to perform reliable but efficient actuation over a sensor network whose topology may change. Actuation on a given group of devices in the sensor network is achieved through a publish operation on the topic the devices in that group are subscribed to. The publication message contains the necessary data to successfully perform the actuation. We make the case for our design showing that: a suitable data distribution techniques and cross-layer optimizations can reduce transmissions within the messaging layer of the sensor-network b a soft-state approach can help with the frequent topology changes in wireless sensor networks caused by the transmission medium. We describe our protocol and compare its features and robustness to those of epidemic protocols through simulation. Our protocol is more efficient when the actuation is performed on selected groups of devices within the sensor network. In the general case, the efficiency of our proposal is similar to that of an epidemic model, plus feedback is given to the initiator of the actuation. Robustness remains close to the epidemic approach, even for moderate bit error rates.
Cryogenic actuator for subnanometer positioning
Bree, B. v.; Janssen, H.; Paalvast, S.; Albers, R.
2012-09-01
This paper discusses the development, realization, and qualification of a positioning actuator concept specifically for cryogenic environments. Originally developed for quantum physics research, the actuator also has many applications in astronomic cryogenic instruments to position optical elements with nanometer level accuracy and stability. Typical applications include the correction of thermally induced position errors of optical components after cooling down from ambient to cryogenic temperatures or sample positioning in microscopes. The actuator is nicknamed the ‘PiezoKnob’ because it is piezo based and it is compatible with the typical manipulator knob often found in standard systems for optical benches, such as linear stages or tip/tilt lens holders. Actuation with high stiffness piezo elements enables the Piezoknob to deliver forces up to 50 Newton which allows relatively stiff guiding mechanisms or large pre-loads. The PiezoKnob has been qualified at 77 Kelvin and was shown to work down to 2 Kelvin. As part of the qualification program, the custom developed driving electronics and set point profile have been fine-tuned, by combing measurements with predictions from a dynamic model, thus maximizing efficiency and minimizing power dissipation. Furthermore, the actuator holds its position without power and thanks to its mechanical layout it is absolutely insensitive to drift of the piezo elements or the driving electronics.
Actuator forces in CFD: RANS and LES modeling in OpenFOAM
Wind turbine wakes are a very challenging topic for scientific computations, but modern CFD frameworks and latest HPC centers allow setting up numerical computations on the wake induced by the wind turbine. The main issues is that the correct modeling of the wake is related to the correct modeling of the interaction between the blade and the incoming flow. The aim of the proposed work is to estimate the aerodynamic forces acting on the blades in order to correctly generate the rotor wake applying equivalent aerodynamic force source on the flow. The definition of a blade forces is done developing a model able to correctly estimate this aerodynamic forces as a function of the local flow seen by the blade during its revolution
Effective Multi-Model Motion Tracking Under Multiple Team Member Actuators
Gu, Yang; Veloso, Manuela
2009-01-01
Motivated by the interactions between a team and the tracked target, we contribute a method to achieve efficient tracking through using a play-based motion model and combined vision and infrared sensory information. This method gives the robot a more exact task-specific motion model when executing different tactics over the tracked target (e.g. the ball) or collaborating with the tracked target (e.g. the team member). Then we represent the system in a compact dynamic Bayesian network and use ...
Lai, William
Inspired by nature, the development of soft actuators has drawn large attention to provide higher flexibility and allow adaptation to more complex environment. This thesis is focused on utilizing electroactive polymers as active materials to develop soft planar dielectric elastomer actuators capable of complex 3D deformation. The potential applications of such soft actuators are in flexible robotic arms and grippers, morphing structures and flapping wings for micro aerial vehicles. The embraces design for a freestanding actuator utilizes the constrained deformation imposed by surface stiffeners on an electroactive membrane to avert the requirement of membrane pre-stretch and the supporting frames. The proposed design increases the overall actuator flexibility and degrees-of-freedom. Actuator design, fabrication, and performance are presented for different arrangement of stiffeners. Digital images correlation technique were utilized to evaluate the in-plane finite strain components, in order to elucidate the role of the stiffeners in controlling the three dimensional deformation. It was found that a key controlling factor was the localized deformation near the stiffeners, while the rest of the membrane would follow through. A detailed finite element modeling framework was developed with a user-material subroutine, built into the ABAQUS commercial finite element package. An experimentally calibrated Neo-Hookean based material model that coupled the applied electrical field to the actuator mechanical deformation was employed. The numerical model was used to optimize different geometrical features, electrode layup and stacking sequence of actuators. It was found that by splitting the stiffeners into finer segments, the force-stroke characteristics of actuator were able to be adjusted with stiffener configuration, while keeping the overall bending stiffness. The efficacy of actuators could also be greatly improved by increasing the stiffener periodicity. The developed
Prognostics Enhanced Reconfigurable Control of Electro-Mechanical Actuators
National Aeronautics and Space Administration — Actuator systems are employed widely in aerospace, transportation and industrial processes to provide power to critical loads, such as aircraft control surfaces....
35 Hz shape memory alloy actuator with bending-twisting mode
Song, Sung-Hyuk; Lee, Jang-Yeob; Rodrigue, Hugo; Choi, Ik-Seong; Kang, Yeon June; Ahn, Sung-Hoon
2016-02-01
Shape Memory Alloy (SMA) materials are widely used as an actuating source for bending actuators due to their high power density. However, due to the slow actuation speed of SMAs, there are limitations in their range of possible applications. This paper proposes a smart soft composite (SSC) actuator capable of fast bending actuation with large deformations. To increase the actuation speed of SMA actuator, multiple thin SMA wires are used to increase the heat dissipation for faster cooling. The actuation characteristics of the actuator at different frequencies are measured with different actuator lengths and results show that resonance can be used to realize large deformations up to 35 Hz. The actuation characteristics of the actuator can be modified by changing the design of the layered reinforcement structure embedded in the actuator, thus the natural frequency and length of an actuator can be optimized for a specific actuation speed. A model is used to compare with the experimental results of actuators with different layered reinforcement structure designs. Also, a bend-twist coupled motion using an anisotropic layered reinforcement structure at a speed of 10 Hz is also realized. By increasing their range of actuation characteristics, the proposed actuator extends the range of application of SMA bending actuators.
Active flow control is a rapidly developing topic because the associated industrial applications are of immense importance, particularly for aeronautics. Among all the flow control methods, such as the use of mechanical flaps or wall jets, plasma-based devices are very promising devices. The main advantages of such systems are their robustness, their simplicity, their low-power consumption and that they allow a real-time control at high frequency. This paper deals with an experimental study about the electric wind produced by a surface discharge based on a three-electrode geometry. This new device is composed of a typical two-electrode surface barrier discharge excited by an AC high voltage, plus a third electrode at which a DC high voltage is applied in order to extend the discharge region and to accelerate the ion drift velocity. In the first part the electrical current of these different surface discharges is presented and discussed. This shows that the current behaviour depends on the DC component polarity. The second part is dedicated to analysing the electric wind characteristics through Schlieren visualizations and to measuring its time-averaged velocity with a Pitot tube sensor. The results show that an excitation of the electrodes with an AC voltage plus a positive DC component can significantly modify the topology of the electric wind produced by a single DBD. In practice, this DC component allows us to increase the value of the maximum induced velocity (up to +150% at a few centimetres downstream of the discharge) and the plasma extension, to enhance the depression occurring above the discharge region and to increase the discharge-induced mass flow rate (up to +100%), without increasing the electrical power consumption
Designing light responsive bistable arches for rapid, remotely triggered actuation
Smith, Matthew L.; Shankar, M. Ravi; Backman, Ryan; Tondiglia, Vincent P.; Lee, Kyung Min; McConney, Michael E.; Wang, David H.; Tan, Loon-Seng; White, Timothy J.
2014-03-01
Light responsive azobenzene functionalized polymer networks enjoy several advantages as actuator candidates including the ability to be remotely triggered and the capacity for highly tunable control via light intensity, polarization, wavelength and material alignments. One signi cant challenge hindering these materials from being employed in applications is their often relatively slow actuation rates and low power densities, especially in the absence of photo-thermal e ects. One well known strategy employed in nature for increasing actuation rate and power output is the storage and quick release of elastic energy (e.g., the Venus ytrap). Using nature as inspiration we have conducted a series of experiments and developed an equilibrium mechanics model for investigating remotely triggered snap-through of bistable light responsive arches made from glassy azobenzene functionalized polymers. After brie y discussing experimental observations we consider in detail a geometrically exact, planar rod model of photomechanical snap-through. Theoretical energy release characteristics and unique strain eld pro les provide insight toward design strategies for improved actuator performance. The bistable light responsive arches presented here are potentially a powerful option for remotely triggered, rapid motion from apparently passive structures in applications such as binary optical switches and positioners, surfaces with morphing topologies, and impulse locomotion in micro or millimeter scale robotics.
On electrostatically actuated NEMS/MEMS circular plates
Caruntu, Dumitru I.; Alvarado, Iris
2011-04-01
This paper deals with electrostatically actuated micro and nano-electromechanical (MEMS/NEMS) circular plates. The system under investigation consists of two bodies, a deformable and conductive circular plate placed above a fixed, rigid and conductive ground plate. The deformable circular plate is electrostatically actuated by applying an AC voltage between the two plates. Nonlinear parametric resonance and pull-in occur at certain frequencies and relatively large AC voltage, respectively. Such phenomena are useful for applications such as sensors, actuators, switches, micro-pumps, micro-tweezers, chemical and mass sensing, and micro-mirrors. A mathematical model of clamped circular MEMS/NEMS electrostatically actuated plates has been developed. Since the model is in the micro- and nano-scale, surface forces, van der Waals and/or Casimir, acting on the plate are included. A perturbation method, the Method of Multiple Scales (MMS), is used for investigating the case of weakly nonlinear MEMS/NEMS circular plates. Two time scales, fast and slow, are considered in this work. The amplitude-frequency and phase-frequency response of the plate in the case of primary resonance are obtained and discussed.
Dielectric Barrier Discharge Plasma Actuator for Flow Control
Opaits, Dmitry, F.
2012-01-01
This report is Part II of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. It includes a Ph.D. dissertation. The period of performance was January 1, 2007 to December 31, 2010. Part I of the final report is the overview published as NASA/CR-2012- 217654. Asymmetric dielectric barrier discharge (DBD) plasma actuators driven by nanosecond pulses superimposed on dc bias voltage are studied experimentally. This produces non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. The approach consisted of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low voltages. In view of practical applications certain questions have been also addressed, such as electrodynamic effects which accompany scaling of the actuators to real size models, and environmental effects of ozone production by the plasma actuators.
Zhang Ying; Ye Liang; Yang Shuo
2015-01-01
A method combining rotor actuator disk model and embedded grid technique is pre-sented in this paper, aimed at predicting the flow fields and aerodynamic characteristics of tilt rotor aircraft in conversion mode more efficiently and effectively. In this method, rotor’s influence is con-sidered in terms of the momentum it impacts to the fluid around it;transformation matrixes among different coordinate systems are deduced to extend actuator method’s utility to conversion mode flow fields’ calculation. Meanwhile, an embedded grid system is designed, in which grids generated around fuselage and actuator disk are regarded as background grid and minor grid respectively, and a new method is presented for‘donor searching’ and‘hole cutting’ during grid assembling. Based on the above methods, flow fields of tilt rotor aircraft in conversion mode are simulated, with three-dimensional Navier–Stokes equations discretized by a second-order upwind finite-volume scheme and an implicit lower–upper symmetric Gauss–Seidel (LU-SGS) time-stepping scheme. Numerical results demonstrate that the proposed CFD method is very effective in simulating the conversion mode flow fields of tilt rotor aircraft.
Zhang Ying
2015-02-01
Full Text Available A method combining rotor actuator disk model and embedded grid technique is presented in this paper, aimed at predicting the flow fields and aerodynamic characteristics of tilt rotor aircraft in conversion mode more efficiently and effectively. In this method, rotor’s influence is considered in terms of the momentum it impacts to the fluid around it; transformation matrixes among different coordinate systems are deduced to extend actuator method’s utility to conversion mode flow fields’ calculation. Meanwhile, an embedded grid system is designed, in which grids generated around fuselage and actuator disk are regarded as background grid and minor grid respectively, and a new method is presented for ‘donor searching’ and ‘hole cutting’ during grid assembling. Based on the above methods, flow fields of tilt rotor aircraft in conversion mode are simulated, with three-dimensional Navier–Stokes equations discretized by a second-order upwind finite-volume scheme and an implicit lower–upper symmetric Gauss–Seidel (LU-SGS time-stepping scheme. Numerical results demonstrate that the proposed CFD method is very effective in simulating the conversion mode flow fields of tilt rotor aircraft.
Model description of surface dielectric barrier discharges for flow control
Lagmich, Y; Callegari, Th; Pitchford, L C; Boeuf, J P [LAPLACE, Universite de Toulouse, CNRS, 118 route de Narbonne, 31062 Toulouse (France)
2008-05-07
This paper presents a study of the development of a surface dielectric barrier discharge in air under conditions similar to those of plasma actuators for flow control. The study is based on results from a 2D fluid model of the discharge in air that provides the space and time evolution of the charged particle densities, electric field and surface charges. The electrohydrodynamic (EHD) force associated with the momentum transfer from charged particles to neutral molecules in the volume above the dielectric layer is also deduced from the model. Results show that the EHD force is important not only during the positive part of the sinusoidal voltage cycle (i.e. when the electrode on top of the dielectric layer plays the role of the anode) but also during the negative part of the cycle (cathode on top of the dielectric layer). During the positive part of the cycle, the EHD force is due to the formation of a positive ion cloud that is periodically interrupted by high current breakdown. The EHD force during the negative part of the cycle is due to the development of a negative ion cloud that continuously grows during the successive high frequency current pulses that form in this regime.
Accurate determination of pull-in voltage and pull-in position is crucial in the design of electrostatically actuated microbeam-based devices. In the past, there have been many works on analytical modeling of the static pull-in of microbeams. However, unlike the static pull-in of microbeams where the analytical models have been well established, there are few works on analytical modeling of the dynamic pull-in of microbeam actuated by a step voltage. This paper presents two analytical approximate models for calculating the dynamic pull-in voltage and pull-in position of a cantilever beam and a clamped–clamped beam, respectively. The effects of the fringing field are included in the two models. The two models are derived based on the energy balance method. An N-order algebraic equation for the dynamic pull-in position is derived. An approximate solution of the N-order algebraic equation yields the dynamic pull-in position and voltage. The accuracy of the present models is verified by comparing their results with the experimental results and the published models available in the literature. (paper)
Enhanced Fault Detection and Isolation in Modern Flight Actuators
Ossmann, Daniel
2013-01-01
Due to their central location in the control system, actuation systems of primary control surfaces in modern, augmented aircraft must show an increased reliability. A traditional approach is based on hardware redundancy. In this way, modern actuation systems of one single control surface consist of up to two actuators and three sensors. These different dynamic subsystems are all prone to faults themselves and can be monitored. This paper presents the setup of a fault detection and diagnosis (...
Surface-complexation models for sorption onto heterogeneous surfaces
This report provides a description of the discrete-logK spectrum model, together with a description of its derivation, and of its place in the larger context of surface-complexation modelling. The tools necessary to apply the discrete-logK spectrum model are discussed, and background information appropriate to this discussion is supplied as appendices. (author)
Magnetic actuators and sensors
Brauer, John R
2014-01-01
An accessible, comprehensive guide on magnetic actuators and sensors, this fully updated second edition of Magnetic Actuators and Sensors includes the latest advances, numerous worked calculations, illustrations, and real-life applications. Covering magnetics, actuators, sensors, and systems, with updates of new technologies and techniques, this exemplary learning tool emphasizes computer-aided design techniques, especially magnetic finite element analysis, commonly used by today's engineers. Detailed calculations, numerous illustrations, and discussions of discrepancies make this text an inva
Gholam reza Tathiri
2014-01-01
Full Text Available In this paper, characteristics of the flow induced in the boundary layer by an AC-Dielectric Barrier Discharge (DBD plasma actuator are compared against those of a DC-corona wind actuator. This is achieved by visualization of the induced flow using smoke injection and measuring the horizontal induced velocity. Our measurements show that the maximum induced velocity of an AC-DBD actuator is about one order of magnitude larger than that of a DC-corona actuator. For an AC-DBD actuator, the induced velocity is maximized on the plate surface while for a DC-corona actuator the induced velocity peaks at about 20mm above the surface. Using flow visualization, we demonstrate that the induced velocity of an AC-DBD actuator is parallel to the surface, while the induced velocity of a DC-corona actuator has components perpendicular to surface.
Surface modeling of soil antibiotics.
Shi, Wen-jiao; Yue, Tian-xiang; Du, Zheng-ping; Wang, Zong; Li, Xue-wen
2016-02-01
Large numbers of livestock and poultry feces are continuously applied into soils in intensive vegetable cultivation areas, and then some veterinary antibiotics are persistent existed in soils and cause health risk. For the spatial heterogeneity of antibiotic residues, developing a suitable technique to interpolate soil antibiotic residues is still a challenge. In this study, we developed an effective interpolator, high accuracy surface modeling (HASM) combined vegetable types, to predict the spatial patterns of soil antibiotics, using 100 surface soil samples collected from an intensive vegetable cultivation area located in east of China, and the fluoroquinolones (FQs), including ciprofloxacin (CFX), enrofloxacin (EFX) and norfloxacin (NFX), were analyzed as the target antibiotics. The results show that vegetable type is an effective factor to be combined to improve the interpolator performance. HASM achieves less mean absolute errors (MAEs) and root mean square errors (RMSEs) for total FQs (NFX+CFX+EFX), NFX, CFX and EFX than kriging with external drift (KED), stratified kriging (StK), ordinary kriging (OK) and inverse distance weighting (IDW). The MAE of HASM for FQs is 55.1 μg/kg, and the MAEs of KED, StK, OK and IDW are 99.0 μg/kg, 102.8 μg/kg, 106.3 μg/kg and 108.7 μg/kg, respectively. Further, RMSE simulated by HASM for FQs (CFX, EFX and NFX) are 106.2 μg/kg (88.6 μg/kg, 20.4 μg/kg and 39.2 μg/kg), and less 30% (27%, 22% and 36%), 33% (27%, 27% and 43%), 38% (34%, 23% and 41%) and 42% (32%, 35% and 51%) than the ones by KED, StK, OK and IDW, respectively. HASM also provides better maps with more details and more consistent maximum and minimum values of soil antibiotics compared with the measured data. The better performance can be concluded that HASM takes the vegetable type information as global approximate information, and takes local sampling data as its optimum control constraints. PMID:26613514
Mathieu Grossard
2016-06-01
Full Text Available Driven by increasing societal, economic, and technological pressures, high-resolution actuators must achieve ever increasing accuracy requirements and functional integration into the system.[...
Lightweight in-plane actuated deformable mirrors for space telescopes
Shepherd, Michael J.
This research focused on lightweight, in-plane actuated, deformable mirrors, with the ultimate goal of developing a 20-meter or larger diameter light gathering aperture for space telescopes. Membrane optics is the study of these structures which may be stowed compactly and unfurled in orbit. This effort comprised four research areas: modelling, analytical solutions, surface control strategy, and scaling. Initially, experimental results were compared to theory using a 0.127 meter diameter deformable mirror testbed. The mirror was modelled using finite elements with MSC.Nastran software, where a boundary tension field was determined using laser vibrometer data. A non-linear solution technique was used to incorporate the membrane stiffening from the applied tension. Statically obtained actuator influence functions were compared to experimentally achieved data, and then a least squares approach was used as the basis for creating a quasi-static control algorithm. Experimental simultaneous tracking of Zernike tip, tilt, and defocus modes was successfully demonstrated. The analytical solutions to plate-membrane and beam-string ordinary differential equation representing the deformable mirror equations were developed. A simplified approach to modelling the axisymmetric cases was also presented. Significantly, it was shown both analytically and through numerical analysis that static actuation for a mirror with a discrete electrode pattern and a high tension-to-stiffness ratio was simply a localized piston displacement in the region of the actuator. Next, a novel static control strategy, the Modal Transformation Method, was developed for membrane mirrors. The method was implemented in finite element simulation, and shows the capability of the in-plane actuated mirror to form Zernike surfaces within an interior, or clear aperture, region using a number of statically-actuated structural modes. Lastly, the scaling problem for membrane optics was addressed. Linear modelling was
Garcia Cartagena, Edgardo Javier; Santoni, Christian; Ciri, Umberto; Iungo, Giacomo Valerio; Leonardi, Stefano
2015-11-01
A large-scale wind farm operating under realistic atmospheric conditions is studied by coupling a meso-scale and micro-scale models. For this purpose, the Weather Research and Forecasting model (WRF) is coupled with an in-house LES solver for wind farms. The code is based on a finite difference scheme, with a Runge-Kutta, fractional step and the Actuator Disk Model. The WRF model has been configured using seven one-way nested domains where the child domain has a mesh size one third of its parent domain. A horizontal resolution of 70 m is used in the innermost domain. A section from the smallest and finest nested domain, 7.5 diameters upwind of the wind farm is used as inlet boundary condition for the LES code. The wind farm consists in six-turbines aligned with the mean wind direction and streamwise spacing of 10 rotor diameters, (D), and 2.75D in the spanwise direction. Three simulations were performed by varying the velocity fluctuations at the inlet: random perturbations, precursor simulation, and recycling perturbation method. Results are compared with a simulation on the same wind farm with an ideal uniform wind speed to assess the importance of the time varying incoming wind velocity. Numerical simulations were performed at TACC (Grant CTS070066). This work was supported by NSF, (Grant IIA-1243482 WINDINSPIRE).
Surface Flux Modeling for Air Quality Applications
Limei Ran
2011-08-01
Full Text Available For many gasses and aerosols, dry deposition is an important sink of atmospheric mass. Dry deposition fluxes are also important sources of pollutants to terrestrial and aquatic ecosystems. The surface fluxes of some gases, such as ammonia, mercury, and certain volatile organic compounds, can be upward into the air as well as downward to the surface and therefore should be modeled as bi-directional fluxes. Model parameterizations of dry deposition in air quality models have been represented by simple electrical resistance analogs for almost 30 years. Uncertainties in surface flux modeling in global to mesoscale models are being slowly reduced as more field measurements provide constraints on parameterizations. However, at the same time, more chemical species are being added to surface flux models as air quality models are expanded to include more complex chemistry and are being applied to a wider array of environmental issues. Since surface flux measurements of many of these chemicals are still lacking, resistances are usually parameterized using simple scaling by water or lipid solubility and reactivity. Advances in recent years have included bi-directional flux algorithms that require a shift from pre-computation of deposition velocities to fully integrated surface flux calculations within air quality models. Improved modeling of the stomatal component of chemical surface fluxes has resulted from improved evapotranspiration modeling in land surface models and closer integration between meteorology and air quality models. Satellite-derived land use characterization and vegetation products and indices are improving model representation of spatial and temporal variations in surface flux processes. This review describes the current state of chemical dry deposition modeling, recent progress in bi-directional flux modeling, synergistic model development research with field measurements, and coupling with meteorological land surface models.
Xu, F; J. Hu; Li, Y.; Zou, J.; Xu, Y; Shang, J.
2013-01-01
Orbital Friction Vibration Actuator (OFVA) is a core component of Orbital Friction Welding (OFW), which is a novel apertureless welding technology utilizing friction heat to implement solid-state joining. In this paper, topology and operational principle of OFVA are introduced, the analytical formulas of the electromagnetic force for the x and y directions, which can drive the mover to generate a circular motion trajectory, are derived, and the characteristic of static electromagnetic fo...
Applications of Dielectric Barrier Discharges and Plasma Synthetic Jet Actuators at ONERA
Chedevergne, F.; Casalis, G; Léon, O.; Forte, M.; Laurendeau, F.; Szulga, N.; Vermeersch, O.; Piot, E.
2015-01-01
This paper focuses on two plasma actuators, developed at ONERA: the DBD actuator (Dielectric Barrier Discharge) and the PSJ actuator (Plasma Synthetic Jet). At the DMAE (Modeling for Aerodynamics and Energetics Department), DBD actuation is investigated for laminar/transition purposes. The results presented deal with 2D configurations including both experimental and modeling works. As regards the activities on the PSJ actuator, most of the work is dedicated to the detailed characterization of...
Flow sensitive actuators for micro-air vehicles
A macrofiber piezoelectric composite has been developed for boundary layer management of micro-air vehicles (MAVs). Specifically, a piezoelectric composite that is capable of self-sensing and controlling flow has been modeled, designed, fabricated, and tested in wind tunnel studies to quantify performance characteristics, such as the velocity field response to actuation, which is relevant for actively managing boundary layers (laminar and transition flow control). A nonlinear piezoelectric plate model was utilized to design the active structure for flow control. The dynamic properties of the piezoelectric composite actuator were also evaluated in situ during wind tunnel experiments to quantify sensing performance. Results based on velocity field measurements and unsteady pressure measurements show that these piezoelectric macrofiber composites can sense the state of flow above the surface and provide sufficient control authority to manipulate the flow conditions for transition from laminar to turbulent flow
Francioso, L.; De Pascali, C.; Pescini, E.; De Giorgi, M. G.; Siciliano, P.
2016-06-01
Preventing the flow separation could enhance the performance of propulsion systems and future civil aircraft. To this end, a fast detection of boundary layer separation is mandatory for a sustainable and successful application of active flow control devices, such as plasma actuators. The present work reports on the design, fabrication and functional tests of low-cost capacitive pressure sensors coupled with dielectric barrier discharge (DBD) plasma actuators to detect and then control flow separation. Finite element method (FEM) simulations were used to obtain information on the deflection and the stress distribution in different-shaped floating membranes. The sensor sensitivity as a function of the pressure load was also calculated by experimental tests. The results of the calibration of different capacitive pressure sensors are reported in this work, together with functional tests in a wind tunnel equipped with a curved wall plate on which a DBD plasma actuator was mounted to control the flow separation. The flow behavior was experimentally investigated by particle image velocimetry (PIV) measurements. Statistical and spectral analysis, applied to the output signals of the pressure sensor placed downstream of the profile leading edge, demonstrated that the sensor is able to discriminate different ionic wind velocity and turbulence conditions. The sensor sensitivity in the 0–100 Pa range was experimentally measured and it ranged between 0.0030 and 0.0046 pF Pa‑1 for the best devices.
Deformable mirrors: design fundamentals for force actuation of continuous facesheets
Ravensbergen, S. K.; Hamelinck, R. F. H. M.; Rosielle, P. C. J. N.; Steinbuch, M.
2009-08-01
Adaptive Optics is established as essential technology in current and future ground based (extremely) large telescopes to compensate for atmospheric turbulence. Deformable mirrors for astronomic purposes have a high number of actuators (> 10k), a relatively large stroke (> 10μm) on a small spacing ( 100Hz). The availability of piezoelectric ceramics as an actuator principle has driven the development of many adaptive deformable mirrors towards inappropriately stiff displacement actuation. This, while the use of force actuation supersedes piezos in performance and longevity while being less costly per channel by a factor of 10-20. This paper presents a model which is independent of the actuator type used for actuation of continuous facesheet deformable mirrors, to study the design parameters such as: actuator spacing & coupling, influence function, peak-valley stroke, dynamical behavior: global & local, etc. The model is validated using finite element simulations and its parameters are used to derive design fundamentals for optimization.
Fuzzy B-Spline Surface Modeling
Rozaimi Zakaria
2014-01-01
Full Text Available This paper discusses the construction of a fuzzy B-spline surface model. The construction of this model is based on fuzzy set theory which is based on fuzzy number and fuzzy relation concepts. The proposed theories and concepts define the uncertainty data sets which represent fuzzy data/control points allowing the uncertainties data points modeling which can be visualized and analyzed. The fuzzification and defuzzification processes were also defined in detail in order to obtain the fuzzy B-spline surface crisp model. Final section shows an application of fuzzy B-spline surface modeling for terrain modeling which shows its usability in handling uncertain data.
Models for Free Granular Surfaces
Mulet, R.; Herrmann, H
2000-01-01
We introduce two sets of continuum equations to describe granular flow on a free surface and study their properties. The equations derived from a microscopic picture that includes jumps and a mobility threshold, account for ripple and crater formation.
Dynamic Factor Models for the Volatility Surface
van der Wel, Michel; Ozturk, Sait R.; Dijk, Dick van
-based models are both rejected against the general dynamic factor model, (ii) the factors driving the surface are highly persistent, (iii) for the restricted models option Delta is preferred over the more often used strike relative to spot price as measure for moneyness.......The implied volatility surface is the collection of volatilities implied by option contracts for different strike prices and time-to-maturity. We study factor models to capture the dynamics of this three-dimensional implied volatility surface. Three model types are considered to examine desirable...... features for representing the surface and its dynamics: a general dynamic factor model, restricted factor models designed to capture the key features of the surface along the moneyness and maturity dimensions, and in-between spline-based methods. Key findings are that: (i) the restricted and spline...
Uncertainties in Surface Layer Modeling
Pendergrass, W.
2015-12-01
A central problem for micrometeorologists has been the relationship of air-surface exchange rates of momentum and heat to quantities that can be predicted with confidence. The flux-gradient profile developed through Monin-Obukhov Similarity Theory (MOST) provides an integration of the dimensionless wind shear expression where is an empirically derived expression for stable and unstable atmospheric conditions. Empirically derived expressions are far from universally accepted (Garratt, 1992, Table A5). Regardless of what form of these relationships might be used, their significance over any short period of time is questionable since all of these relationships between fluxes and gradients apply to averages that might rarely occur. It is well accepted that the assumption of stationarity and homogeneity do not reflect the true chaotic nature of the processes that control the variables considered in these relationships, with the net consequence that the levels of predictability theoretically attainable might never be realized in practice. This matter is of direct relevance to modern prognostic models which construct forecasts by assuming the universal applicability of relationships among averages for the lower atmosphere, which rarely maintains an average state. Under a Cooperative research and Development Agreement between NOAA and Duke Energy Generation, NOAA/ATDD conducted atmospheric boundary layer (ABL) research using Duke renewable energy sites as research testbeds. One aspect of this research has been the evaluation of legacy flux-gradient formulations (the ϕ functions, see Monin and Obukhov, 1954) for the exchange of heat and momentum. At the Duke Energy Ocotillo site, NOAA/ATDD installed sonic anemometers reporting wind and temperature fluctuations at 10Hz at eight elevations. From these observations, ϕM and ϕH were derived from a two-year database of mean and turbulent wind and temperature observations. From this extensive measurement database, using a
An electrochemical micro actuator
Hamberg, M.W.; Neagu, C.R.; Gardeniers, J.G.E.; IJntema, D.J.; Elwenspoek, M.C.
1995-01-01
In this paper an investigation of the feasibility of a new electrochemical micro actuator is presented. The actuator is fabricated using silicon micro-machining techniques. A gas pressure is generated by electrolysis of an aqueous electrolyte solution. The build up pressure is used to change the def
Bergveld, P.
1989-01-01
This paper describes the organization and the research programme of the Sensor and Actuator (S&A) Research Unit of the University of Twente, Enschede, the Netherlands. It includes short descriptions of all present projects concerning: micromachined mechanical sensors and actuators, optical sensors,
Conjugated polymers as actuators: modes of actuation
Skaarup, Steen
The physical and chemical properties of conjugated polymers often depend very strongly on the degree of doping with anions or cations. The movement of ions in and out of the polymer matrix as it is redox cycled is also accompanied by mechanical changes. Both the volume and the stiffness can exhibit...... significant differences between the oxidized and reduced states. These effects form the basis of the use of conjugated polymers as actuators (or “artificial muscles”) controllable by a small (1-10 V) voltage. Three basic modes of actuation (bending, linear extension and stiffness change) have been proposed...
Conjugated Polymers as Actuators: Modes of Actuation
Skaarup, Steen
The physical and chemical properties of conjugated polymers often depend very strongly on the degree of doping with anions or cations. The movement of ions in and out of the polymer matrix as it is redox cycled is also accompanied by mechanical changes. Both the volume and the stiffness can exhibit...... significant differences between the oxidized and reduced states. These effects form the basis of the use of conjugated polymers as actuators (or “artificial muscles”) controllable by a small (1-10 V) voltage. Three basic modes of actuation (bending, linear extension and stiffness change) have been proposed...
Analysis of a spherical permanent magnet actuator
This paper describes a new form of actuator with a spherical permanent magnet rotor and a simple winding arrangement, which is capable of a high specific torque by utilizing a rare-earth permanent magnet. The magnetic-field distribution is established using an analytical technique formulated in spherical coordinates, and the results are validated by finite element analysis. The analytical field solution allows the prediction of the actuator torque and back emf in closed forms. In turn, these facilitate the characterization of the actuator and provide a firm basis for design optimization, system dynamic modeling, and closed-loop control law development. copyright 1997 American Institute of Physics
Dynamical Modeling of Surface Tension
Brackbill, Jeremiah U.; Kothe, Douglas B.
1996-01-01
In a recent review it is said that free-surface flows 'represent some of the difficult remaining challenges in computational fluid dynamics'. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF formulation might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin (1996). This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated. For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin (1996), are discussed.
This study concerns new investigation of active vibration reduction of a stiffened plate bonded with discrete sensor/actuator pairs located optimally using genetic algorithms based on a developed finite element modeling. An isotropic plate element stiffened by a number of beam elements on its edges and having a piezoelectric sensor and actuator pair bonded to its surfaces is modeled using the finite element method and Hamilton’s principle, taking into account the effects of piezoelectric mass, stiffness and electromechanical coupling. The modeling is based on the first order shear deformation theory taking into account the effects of bending, membrane and shear deformation for the plate, the stiffening beam and the piezoelectric patches. A Matlab finite element program has been built for the stiffened plate model and verified with ANSYS and also experimentally. Optimal placement of ten piezoelectric sensor/actuator pairs and optimal feedback gain for active vibration reduction are investigated for a plate stiffened by two beams arranged in the form of a cross. The genetic algorithm was set up for optimization of sensor/actuator placement and feedback gain based on the minimization of the optimal linear quadratic index as an objective function to suppress the first six modes of vibration. Comparison study is presented for active vibration reduction of a square cantilever plate stiffened by crossed beams with two sensor/actuator configurations: firstly, ten piezoelectric sensor/actuator pairs are located in optimal positions; secondly, a piezoelectric layer of single sensor/actuator pair covering the whole of the stiffened plate as a SISO system. (paper)
Mechatronics and Bioinspiration in Actuator Design and Control
J. L. Pons
2008-01-01
Full Text Available Actuators are components of motion control systems in which mechatronics plays a crucial role. They can be regarded as a paradigmatic case in which this mechatronic approach is required. Furthermore, actuator technologies can get new sources of inspiration from nature (bioinspiration. Biological systems are the result of an evolutionary process and show excellent levels of performance. In this paper, we analyse the actuator as a bioinspired mechatronic system through analogies between mechatronics and biological actuating mechanisms that include hierarchical control of actuators, switched control of power flow and some transduction principles. Firstly, some biological models are introduced as a source of inspiration for setting up both actuation principles and control technologies. Secondly, a particular actuator technology, the travelling wave ultrasonic motor, is taken to illustrate this approach. Eventually, the last section draws some conclusions and points out future directions.
Advanced actuators for the control of large space structures
Downer, James; Hockney, Richard; Johnson, Bruce; Misovec, Kathleen
1993-01-01
The objective of this research was to develop advanced six-degree-of-freedom actuators employing magnetic suspensions suitable for the control of structural vibrations in large space structures. The advanced actuators consist of a magnetically suspended mass that has three-degrees-of-freedom in both translation and rotation. The most promising of these actuators featured a rotating suspended mass providing structural control torques in a manner similar to a control moment gyro (CMG). These actuators employ large-angle-magnetic suspensions that allow gimballing of the suspended mass without mechanical gimbals. Design definitions and sizing algorithms for these CMG type as well as angular reaction mass actuators based on multi-degree-of-freedom magnetic suspensions were developed. The performance of these actuators was analytically compared with conventional reaction mass actuators for a simple space structure model.
Efficient Hybrid Actuation Using Solid-State Actuators
Leo, Donald J.; Cudney, Harley H.; Horner, Garnett (Technical Monitor)
2001-01-01
Piezohydraulic actuation is the use of fluid to rectify the motion of a piezoelectric actuator for the purpose of overcoming the small stroke limitations of the material. In this work we study a closed piezohydraulic circuit that utilizes active valves to rectify the motion of a hydraulic end affector. A linear, lumped parameter model of the system is developed and correlated with experiments. Results demonstrate that the model accurately predicts the filtering of the piezoelectric motion caused by hydraulic compliance. Accurate results are also obtained for predicting the unidirectional motion of the cylinder when the active valves are phased with respect to the piezoelectric actuator. A time delay associated with the mechanical response of the valves is incorporated into the model to reflect the finite time required to open or close the valves. This time delay is found to be the primary limiting factor in achieving higher speed and greater power from the piezohydraulic unit. Experiments on the piezohydraulic unit demonstrate that blocked forces on the order of 100 N and unloaded velocities of 180 micrometers/sec are achieved.
Surface modification with ionised cluster beams: Modelling
Impacts of accelerated cluster ions which consist of hundreds of atoms on a solid surface have shown new surface smoothing and roughening effects. Hybrid Molecular Dynamics (MD) and a two-dimensional MD method were used to simulate rapid collision processes at the target impact zone and the subsequent thermalization. Gas clusters impacting on metal and semiconductor target surfaces have been considered to study the ripple formation under irradiation with oblique cluster beams. The dynamics of surface modification is simulated by using a discrete model which contains crater formation and surface relaxation. The continuum description of a surface relaxation is based on a dynamics equation for surface heights containing viscous flow, surface tension, surface diffusion, and crater formation terms. Comparison of the results of the simulation with experimental data shows qualitative agreement
In the present study, a biomimetic flexible flapping wing was developed on a real ornithopter scale by using macro-fiber composite (MFC) actuators. With the actuators, the maximum camber of the wing can be linearly changed from −2.6% to +4.4% of the maximum chord length. Aerodynamic tests were carried out in a low-speed wind tunnel to investigate the aerodynamic characteristics, particularly the camber effect, the chordwise flexibility effect and the unsteady effect. Although the chordwise wing flexibility reduces the effective angle of attack, the maximum lift coefficient can be increased by the MFC actuators up to 24.4% in a static condition. Note also that the mean values of the perpendicular force coefficient rise to a value of considerably more than 3 in an unsteady aerodynamic flow region. Additionally, particle image velocimetry (PIV) tests were performed in static and dynamic test conditions to validate the flexibility and unsteady effects. The static PIV results confirm that the effective angle of attack is reduced by the coupling of the chordwise flexibility and the aerodynamic force, resulting in a delay in the stall phenomena. In contrast to the quasi-steady flow condition of a relatively high advance ratio, the unsteady aerodynamic effect due to a leading edge vortex can be found along the wing span in a low advance ratio region. The overall results show that the chordwise wing flexibility can produce a positive effect on flapping aerodynamic characteristics in quasi-steady and unsteady flow regions; thus, wing flexibility should be considered in the design of efficient flapping wings
Mirrors Containing Biomimetic Shape-Control Actuators
Bar-Cohen, Yoseph; Mouroulis, Pantazis; Bao, Xiaoqi; Sherrit, Stewart
2003-01-01
Curved mirrors of a proposed type would comprise lightweight sheets or films containing integral, biologically inspired actuators for controlling their surface figures. These mirrors could be useful in such applications as collection of solar energy, focusing of radio beams, and (provided sufficient precision could be achieved) imaging. These mirrors were originally intended for use in outer space, but it should also be possible to develop terrestrial versions. Several prior NASA Tech Briefs articles have described a variety of approaches to the design of curved, lightweight mirrors containing integral shape-control actuators. The primary distinction between the present approach and the prior approaches lies in the actuator design concept, which involves shapes and movements reminiscent of those of a variety of small, multi-armed animals. The shape and movement of an actuator of this type can also be characterized as reminiscent of that of an umbrella. This concept can be further characterized as a derivative of that of multifinger grippers, the fingers of which are bimorph bending actuators (see Figure 1). The fingers of such actuators can be strips containing any of a variety of materials that have been investigated for use as actuators, including such electroactive polymers as ionomeric polymer/metal composites (IPMCs), ferroelectric polymers, and grafted elastomers. A mirror according to this proposal would be made from a sheet of one of the actuator composites mentioned above. The design would involve many variables, including the pre-curvature and stiffness of the mirror sheet, the required precision of figure control, the required range of variation in focal length (see Figure 2), the required precision of figure control for imaging or non-imaging use, the bending and twisting moments needed to effect the required deformations, and voltage-tomoment coefficients of the actuators, and the voltages accordingly required for actuation. A typical design would call
Numerical simulation of aerodynamic plasma actuator effects
da Silva Del Rio Vieira, Debora Gleice
2013-01-01
The present work used an in-house code (FASTEST) for solving the incompressible Navier-Stokes equations with Finite Volume Method applied to the flow over a flat plate influenced by plasma actuators. The actuators were modeled using experimental data (from PIV) for a precise evaluation of the plasma body force and its fluid mechanic effects. This method is proven and found to have a good accuracy suitable for a quantitative analysis of the proposed test cases. Tollmien-Schlichting waves were ...
Evaluation of linear DC motor actuators for control of large space structures
Ide, Eric Nelson
1988-01-01
This thesis examines the use of a linear DC motor as a proof mass actuator for the control of large space structures. A model for the actuator, including the current and force compensation used, is derived. Because of the force compensation, the actuator is unstable when placed on a structure. Relative position feedback is used for actuator stabilization. This method of compensation couples the actuator to the mast in a feedback configuration. Three compensator designs are prop...
A low-power-consumption out-of-Plane electrothermal actuator
Girbau Sala, David; Llamas Morote, Marco Antonio; Casals Terré, Jasmina; Simó Selvas, Francisco Javier; Pradell i Cara, Lluís; Lázaro Guillén, Antoni
2007-01-01
This paper proposes a new vertical electrothermal actuator. It can be considered as a hybrid between the traditional in-plane buckle-beam actuator and the vertical hot-cold actuator. It is here referred to as vertical buckle beam. At identical dimensional and bias conditions, it features a displacement larger than that of other vertical electrothermal actuators proposed so far in the literature. The actuator performance is demonstrated by means of an analytical model along with finite-element...
Cruise and turning performance of an improved fish robot actuated by piezoceramic actuators
Nguyen, Quang Sang; Heo, Seok; Park, Hoon Cheol; Goo, Nam Seo; Byun, Doyoung
2009-03-01
The purpose of this study is improvement of a fish robot actuated by four light-weight piezocomposite actuators (LIPCAs). In the fish robot, we developed a new actuation mechanism working without any gear and thus the actuation mechanism was simple in fabrication. By using the new actuation mechanism, cross section of the fish robot became 30% smaller than that of the previous model. Performance tests of the fish robot in water were carried out to measure tail-beat angle, thrust force, swimming speed and turning radius for tail-beat frequencies from 1Hz to 5Hz. The maximum swimming speed of the fish robot was 7.7 cm/s at 3.9Hz tail-beat frequency. Turning experiment showed that swimming direction of the fish robot could be controlled with 0.41 m turning radius by controlling tail-beat angle.
Surface Flux Modeling for Air Quality Applications
Limei Ran; Jonathan Pleim
2011-01-01
For many gasses and aerosols, dry deposition is an important sink of atmospheric mass. Dry deposition fluxes are also important sources of pollutants to terrestrial and aquatic ecosystems. The surface fluxes of some gases, such as ammonia, mercury, and certain volatile organic compounds, can be upward into the air as well as downward to the surface and therefore should be modeled as bi-directional fluxes. Model parameterizations of dry deposition in air quality models have been represented by...
Model Eliashberg functions for surface states
Nojima, A. [Department of Chemical System Engineering, School of Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan)], E-mail: nojima@tcl.t.u-tokyo.ac.jp; Yamashita, K. [Department of Chemical System Engineering, School of Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan); Hellsing, B. [Department of Physics, Goeteborg University, Fysikgraend 3, S-412, 96 Goeteborg (Sweden)
2008-09-30
We present a simplified procedure for the analysis of the phonon-induced lifetimes of surface states. The model includes information about the electron and phonon structure and is thus more reliable than procedures based on phonon Debye models. We apply the model to calculate the lifetime broadening of Cu(1 1 1) and Al(0 0 1) surface states. The obtained Eliashberg functions and lifetimes are in reasonable agreement with previous detailed studies.
Considerations for Contractile Electroactive Materials and Actuators
Lenore Rasmussen, David Schramm, Paul Rasmussen, Kevin Mullaly, Ras Labs, LLC, Intelligent Materials for Prosthetics & Automation, Lewis D. Meixler, Daniel Pearlman and Alice Kirk
2011-05-23
Ras Labs produces contractile electroactive polymer (EAP) based materials and actuators that bend, swell, ripple, and contract (new development) with low electric input. In addition, Ras Labs produces EAP materials that quickly contract and expand, repeatedly, by reversing the polarity of the electric input, which can be cycled. This phenomenon was explored using molecular modeling, followed by experimentation. Applied voltage step functions were also investigated. High voltage steps followed by low voltage steps produced a larger contraction followed by a smaller contraction. Actuator control by simply adjusting the electric input is extremely useful for biomimetic applications. Muscles are able to partially contract. If muscles could only completely contract, nobody could hold an egg, for example, without breaking it. A combination of high and low voltage step functions could produce gross motor function and fine manipulation within the same actuator unit. Plasma treated electrodes with various geometries were investigated as a means of providing for more durable actuation.
Implicitly modelled stratigraphic surfaces using generalized interpolation
Hillier, Michael; de Kemp, Eric; Schetselaar, Ernst
2016-06-01
Stratigraphic surfaces implicitly modelled using a generalized interpolation approach in various geological settings is presented to demonstrate its modelling capabilities and limitations. The generalized interpolation approach provides a useful mathematical framework in modelling continuous surfaces from scattered data consisting of the following geological constraints: contact locations and planar orientations. Examples are presented to show the effectiveness of the method in generating plausible representations of geological structures in sparse data environments. One of the major advantages of implicit surface modelling has long been claimed as its ability to model geometries with arbitrary topology. It is, however, demonstrated that this is in fact a disadvantage in robustly generating geologically realistic surfaces in structurally complex domains with a known topology.
Muscle Motion Solenoid Actuator
Obata, Shuji
It is one of our dreams to mechanically recover the lost body for damaged humans. Realistic humanoid robots composed of such machines require muscle motion actuators controlled by all pulling actions. Particularly, antagonistic pairs of bi-articular muscles are very important in animal's motions. A system of actuators is proposed using the electromagnetic force of the solenoids with the abilities of the stroke length over 10 cm and the strength about 20 N, which are needed to move the real human arm. The devised actuators are based on developments of recent modern electro-magnetic materials, where old time materials can not give such possibility. Composite actuators are controlled by a high ability computer and software making genuine motions.
Pinera, Alex
2013-01-01
This invention is a magnetically actuated seal in which either a single electromagnet, or multiple electromagnets, are used to control the seal's position. This system can either be an open/ close type of system or an actively controlled system.
Magnetically Actuated Seal Project
National Aeronautics and Space Administration — FTT proposes development of a magnetically actuated dynamic seal. Dynamic seals are used throughout the turbopump in high-performance, pump-fed, liquid rocket...
Actuator characterization of a man-portable precision maneuver concept
Ilmars Celmins
2014-06-01
Full Text Available The US Army Research Laboratory is conducting research to explore technologies that may be suitable for maneuvering man-portable munitions. Current research is focused on the use of rotary actuators with spin-stabilized munitions. A rotary actuator holds the potential of providing a low-power solution for guidance of a spinning projectile. This is in contrast to a linear (reciprocating actuator which would need to constantly change direction, resulting in large accelerations which in turn would require large forces, thereby driving up the actuator power. A rotational actuator would be operating at a fairly constant rotation rate once it is up to speed, resulting in much lower power requirements. Actuator experiments conducted over a variety of conditions validate the dynamic models of the actuator and supply the data necessary for model parameter estimation. Actuator performance metrics of spin rate response, friction, and power requirements were derived from the data. This study indicates that this class of maneuver concepts can be driven with these actuators. These results enable actuator design and multi-disciplinary simulation of refined maneuver concepts for a specific application.
Actuator characterization of a man-portable precision maneuver concept
Ilmars CELMINS; Frank E.FRESCONI; Bryant P.NELSON
2014-01-01
The US Army Research Laboratory is conducting research to explore technologies that may be suitable for maneuvering man-portable munitions. Current research is focused on the use of rotary actuators with spin-stabilized munitions. A rotary actuator holds the potential of providing a low-power solution for guidance of a spinning projectile. This is in contrast to a linear (reciprocating) actuator which would need to constantly change direction, resulting in large accelerations which in turn would require large forces, thereby driving up the actuator power. A rotational actuator would be operating at a fairly constant rotation rate once it is up to speed, resulting in much lower power requirements. Actuator experiments conducted over a variety of conditions validate the dynamic models of the actuator and supply the data necessary for model parameter estimation. Actuator performance metrics of spin rate response, friction, and power requirements were derived from the data. This study indicates that this class of maneuver concepts can be driven with these actuators. These results enable actuator design and multi-disciplinary simulation of refined maneuver concepts for a specific application.
Vandehey, N. T.; O'Neil, J.P.
2015-01-01
Introduction We have developed a low-cost stopcock valve actuator for radiochemistry automation built using a stepper motor and an Arduino, an open-source single-board microcontroller. The con-troller hardware can be programmed to run by serial communication or via two 5–24 V digital lines for simple integration into any automation control system. This valve actuator allows for automated use of a single, disposable stopcock, providing a number of advantages over stopcock manifold systems ...
Laser Initiated Actuator study
Watson, B.
1991-06-27
The program task was to design and study a laser initiated actuator. The design of the actuator is described, it being comprised of the fiber and body subassemblies. The energy source for all experiments was a Spectra Diode 2200-H2 laser diode. The diode is directly coupled to a 100 micron core, 0.3 numerical aperture fiber optic terminated with an SMA connector. The successful testing results are described and recommendations are made.
Combustion powered linear actuator
Fischer, Gary J.
2007-09-04
The present invention provides robotic vehicles having wheeled and hopping mobilities that are capable of traversing (e.g. by hopping over) obstacles that are large in size relative to the robot and, are capable of operation in unpredictable terrain over long range. The present invention further provides combustion powered linear actuators, which can include latching mechanisms to facilitate pressurized fueling of the actuators, as can be used to provide wheeled vehicles with a hopping mobility.
Dielectric Actuation of Polymers
Niu, Xiaofan
2013-01-01
Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy den...
An Improved MUSIC Model for Gibbsite Surfaces
Mitchell, Scott C.; Bickmore, Barry R.; Tadanier, Christopher J.; Rosso, Kevin M.
2004-06-01
Here we use gibbsite as a model system with which to test a recently published, bond-valence method for predicting intrinsic pKa values for surface functional groups on oxides. At issue is whether the method is adequate when valence parameters for the functional groups are derived from ab initio structure optimization of surfaces terminated by vacuum. If not, ab initio molecular dynamics (AIMD) simulations of solvated surfaces (which are much more computationally expensive) will have to be used. To do this, we had to evaluate extant gibbsite potentiometric titration data that where some estimate of edge and basal surface area was available. Applying BET and recently developed atomic force microscopy methods, we found that most of these data sets were flawed, in that their surface area estimates were probably wrong. Similarly, there may have been problems with many of the titration procedures. However, one data set was adequate on both counts, and we applied our method of surface pKa int prediction to fitting a MUSIC model to this data with considerable success—several features of the titration data were predicted well. However, the model fit was certainly not perfect, and we experienced some difficulties optimizing highly charged, vacuum-terminated surfaces. Therefore, we conclude that we probably need to do AIMD simulations of solvated surfaces to adequately predict intrinsic pKa values for surface functional groups.
Aizenberg, Joanna; Aizenberg, Michael; Kim, Philseok
2016-01-05
Microstructured hybrid actuator assemblies in which microactuators carrying designed surface properties to be revealed upon actuation are embedded in a layer of responsive materials. The microactuators in a microactuator array reversibly change their configuration in response to a change in the environment without requiring an external power source to switch their optical properties.
Potential/charge induced nanoporous metal actuators.
Viswanath, R N
2009-01-01
The mechanical response to the electrochemical charging of nanoporous metals with their pore space wetted by electrolyte have been studied in-situ using dilatometry and wide angle x-ray diffractometry techniques. The actuation strain reported in this manuscript is purely elastic and completely reversible. The capacitive double layer charging became more effective near to the potential to zero charge (pzc) and contribute significantly to the variations of surface stress and crystal strain. In a suitable experimental setup, the actuator effect from porous metals can be amplified, where deliberate movements of the actuator parts are desirable with minimum external force, suggesting that metallic foam-like materials with high surface to volume ratio could be used to mimic natural muscles. PMID:19964917
Cylinder Flow Control Using Plasma Actuators
Kozlov, Alexey; Thomas, Flint
2007-11-01
In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. Two optimized quartz dielectric plasma actuators mounted on the cylinder surface utilizing an improved saw-tooth waveform high-voltage generator allowed flow control at Reynolds number approaching supercritical. Using either steady or unsteady actuation, it is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. PIV based flow fields and wake velocity profiles obtained with hot-wire anemometry show large reductions in vortex shedding, wake width and turbulence intensity.
Frequency response of IPMC actuator with palladium electrode
Kobayashi, T.; Omiya, M.
2011-04-01
The present study investigates the frequency response of IPMC actuator. By using the electroless plating method, IPMC actuator with palladium electrode was obtained in 60 minutes, which was shorter than the conventional fabrication time. In the observation of response to step voltages, IPMC actuator with palladium electrode showed larger deformation and slower backward motion than the conventional IPMC actuators with platinum electrode. In the experiments of frequency response, IPMC actuator showed the resonance phenomenon at a specified frequency, and the resonance frequency could be predicted by the simple cantilever beam model. Then, the phase shift increased drastically when the resonance phenomena were observed. Finally, the frequency response of IPMC actuator was modeled by using the transfer function.
A Review of Surface Water Quality Models
Qinggai Wang; Shibei Li; Peng Jia; Changjun Qi; Feng Ding
2013-01-01
Surface water quality models can be useful tools to simulate and predict the levels, distributions, and risks of chemical pollutants in a given water body. The modeling results from these models under different pollution scenarios are very important components of environmental impact assessment and can provide a basis and technique support for environmental management agencies to make right decisions. Whether the model results are right or not can impact the reasonability and scientificity of...
Cavarec, P.E.
2002-11-15
The aim of this thesis is the study and the conception of splitted structures of global coil synchronous machines for the maximization of specific torque or thrust. This concept of machine, called multi-air gap, is more precisely applied to the elaboration of a new linear multi-rods actuator. It is clearly connected to the context of direct drive solutions. First, a classification of different electromagnetic actuator families gives the particular place of multi-air gaps actuators. Then, a study, based on geometrical parameters optimizations, underlines the interest of that kind of topology for reaching very high specific forces and mechanical dynamics. A similitude law, governing those actuators, is then extracted. A study of mechanical behaviour, taking into account mechanic (tolerance) and normal forces (guidance), is carried out. Hence, methods for filtering the ripple force, and decreasing the parasitic forces without affecting the useful force are presented. This approach drives to the multi-rods structures. A prototype is then tested and validates the feasibility of that kind of devices, and the accuracy of the magnetic models. This motor, having only eight rods for an active volume of one litre, reaches an electromagnetic force of 1000 N in static conditions. A method for estimate optimal performances of multi-rods actuators under several mechanical stresses is presented. (author)
Carbon nanotube based NEMS actuators and sensors
Forney, Michael; Poler, Jordan
2011-03-01
Single-walled carbon nanotubes (SWNTs) have been widely studied due to superior mechanical and electrical properties. We have grown vertically aligned SWNTs (VA-SWNTs) onto microcantilever (MC) arrays, which provides an architecture for novel actuators and sensors. Raman spectroscopy confirms that the CVD-grown nanotubes are SWNTs and SEM confirms aligned growth. As an actuator, this hybrid MC/VA-SWNT system can be electrostatically modulated. SWNTs are excellent electron acceptors, so we can charge up the VA-SWNT array by applying a voltage. The electrostatic repulsion among the charged SWNTs provides a surface stress that induces MC deflection. Simulation results show that a few electrons per SWNT are needed for measureable deflections, and experimental actuators are being characterized by SEM, Raman, and an AFM optical lever system. The applied voltage is sinusoidally modulated, and deflection is measured with a lock-in amplifier. These actuators could be used for nano-manipulation, release of drugs from a capsule, or nano-valves. As a sensor, this MC/VA-SWNT system offers an improved sensitivity for chemical and bio-sensing compared to surface functionalized MC-based sensors. Those sensors only have a 2D sensing surface, but a MC/VA-SWNT system has significantly more sensing surface because the VA-SWNTs extend microns off the MC surface.
Simulating cyclic voltammograms of bimetallic model surfaces
Cyclic voltammograms recorded at bimetallic surfaces reflect the superposition of current contributions from adsorption, desorption, and reaction processes at surface regions with laterally varying chemical properties. As will be demonstrated for some selected well-defined single crystalline model systems including Pt films on Ru(0001) and PtAu/Pt(111) surface alloys, voltammetric features at bimetallic surfaces can be simulated using the corresponding features for the monometallic surfaces in combination with information on the adsorption properties and abundance of the dominating sites at the bimetallic surfaces. Trends in the local adsorption properties can be predicted based on density functional theory calculations, whereas the necessary information about the local vertical and lateral metal distribution is obtained from scanning tunnelling microscopy imaging.
Nanoporous Carbide-Derived Carbon Material-Based Linear Actuators
Janno Torop
2009-12-01
Full Text Available Devices using electroactive polymer-supported carbon material can be exploited as alternatives to conventional electromechanical actuators in applications where electromechanical actuators have some serious deficiencies. One of the numerous examples is precise microactuators. In this paper, we show for first time the dilatometric effect in nanocomposite material actuators containing carbide-derived carbon (CDC and polytetrafluoroetylene polymer (PTFE. Transducers based on high surface area carbide-derived carbon electrode materials are suitable for short range displacement applications, because of the proportional actuation response to the charge inserted, and high Coulombic efficiency due to the EDL capacitance. The material is capable of developing stresses in the range of tens of N cm-2. The area of an actuator can be dozens of cm2, which means that forces above 100 N are achievable. The actuation mechanism is based on the interactions between the high-surface carbon and the ions of the electrolyte. Electrochemical evaluations of the four different actuators with linear (longitudinal action response are described. The actuator electrodes were made from two types of nanoporous TiC-derived carbons with surface area (SA of 1150 m2 g-1 and 1470 m2 g-1, respectively. Two kinds of electrolytes were used in actuators: 1.0 M tetraethylammonium tetrafluoroborate (TEABF4 solution in propylene carbonate and pure ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf. It was found that CDC based actuators exhibit a linear movement of about 1% in the voltage range of 0.8 V to 3.0 V at DC. The actuators with EMITf electrolyte had about 70% larger movement compared to the specimen with TEABF4 electrolyte.
Development and Analysis of Flexible Thin Actuator with a Built-in Fluid Pressure Source
Senzaki Shinji
2016-01-01
Full Text Available A flexible thin actuator using gas-liquid phase-change of a low boiling point liquid that can generate large force was proposed and tested in the previous study. The tested actuator is an envelope-type actuator that is made of laminating plastic sheets, low boiling point liquid and a flexible heater. In this paper, the analytical model of the flexible thin actuator was proposed and tested. The system parameters of the actuator were also identified. As a result, it was confirmed that the proposed analytical model can predict the behaviour of the tested actuator.
A Parallel Approach To Optimum Actuator Selection With a Genetic Algorithm
Rogers, James L.
2000-01-01
Recent discoveries in smart technologies have created a variety of aerodynamic actuators which have great potential to enable entirely new approaches to aerospace vehicle flight control. For a revolutionary concept such as a seamless aircraft with no moving control surfaces, there is a large set of candidate locations for placing actuators, resulting in a substantially larger number of combinations to examine in order to find an optimum placement satisfying the mission requirements. The placement of actuators on a wing determines the control effectiveness of the airplane. One approach to placement Maximizes the moments about the pitch, roll, and yaw axes, while minimizing the coupling. Genetic algorithms have been instrumental in achieving good solutions to discrete optimization problems, such as the actuator placement problem. As a proof of concept, a genetic has been developed to find the minimum number of actuators required to provide uncoupled pitch, roll, and yaw control for a simplified, untapered, unswept wing model. To find the optimum placement by searching all possible combinations would require 1,100 hours. Formulating the problem and as a multi-objective problem and modifying it to take advantage of the parallel processing capabilities of a multi-processor computer, reduces the optimization time to 22 hours.
Modeling and Inversion of Scattered Surface waves
Riyanti, C.D.
2005-01-01
In this thesis, we present a modeling method based on a domain-type integral representation for waves propagating along the surface of the Earth which have been scattered in the vicinity of the source or the receivers. Using this model as starting point, we formulate an inversion scheme to estimat
SOIL CHEMISTRY AND MINERALOGY: SURFACE COMPLEXATION MODELING
Ion adsorption in soils has been described using both empirical and chemical models. Empirical adsorption isotherm equations will be presented and their limitations discussed. Chemical surface complexation models and their applications to soils will be introduced. Advantages and limitations of su...
Effect of actuation sequence on flow rates of peristaltic micropumps with PZT actuators.
Jang, Ling-Sheng; Shu, Kuan; Yu, Yung-Chiang; Li, Yuan-Jie; Chen, Chiun-Hsun
2009-02-01
Many biomedical applications require the administration of drugs at a precise and preferably programmable rate. The flow rate generated by the peristaltic micropumps used in such applications depends on the actuation sequence. Accordingly, the current study performs an analytical and experimental investigation to determine the correlation between the dynamic response of the diaphragms in the micropump and the actuation sequence. A simple analytical model of a peristaltic micropump is established to analyze the shift in the resonant frequency of the diaphragms caused by the viscous damping effect. The analytical results show that this damping effect increases as the oscillation frequency of the diaphragm increases. A peristaltic micropump with three piezoelectric actuators is fabricated on a silicon substrate and is actuated using 2-, 3-, 4- and 6-phase actuation sequences via a driving system comprising a microprocessor and a phase controller. A series of experiments is conducted using de-ionized water as the working fluid to determine the diaphragm displacement and the flow rates induced by each of the different actuation sequences under phase frequencies ranging from 50 Hz to 1 MHz. The results show that the damping effect of actuation sequences influences diaphragm resonant frequency, which in turn affects the profiles of flow rates. PMID:18821016
Computer Modelling of 3D Geological Surface
Kodge B. G.
2011-02-01
Full Text Available The geological surveying presently uses methods and tools for the computer modeling of 3D-structures of the geographical subsurface and geotechnical characterization as well as the application of geoinformation systems for management and analysis of spatial data, and their cartographic presentation. The objectives of this paper are to present a 3D geological surface model of Latur district in Maharashtra state of India. This study is undertaken through the several processes which are discussed in this paper to generate and visualize the automated 3D geological surface model of a projected area.
Computer Modelling of 3D Geological Surface
Kodge, B G
2011-01-01
The geological surveying presently uses methods and tools for the computer modeling of 3D-structures of the geographical subsurface and geotechnical characterization as well as the application of geoinformation systems for management and analysis of spatial data, and their cartographic presentation. The objectives of this paper are to present a 3D geological surface model of Latur district in Maharashtra state of India. This study is undertaken through the several processes which are discussed in this paper to generate and visualize the automated 3D geological surface model of a projected area.
Ken Thomas; Ted Quinn; Jerry Mauck; Richard Bockhorst
2014-09-01
There are significant developments underway in new types of actuators for power plant active components. Many of these make use of digital technology to provide a wide array of benefits in performance of the actuators and in reduced burden to maintain them. These new product offerings have gained considerable acceptance in use in process plants. In addition, they have been used in conventional power generation very successfully. This technology has been proven to deliver the benefits promised and substantiate the claims of improved performance. The nuclear industry has been reluctant to incorporate digital actuator technology into nuclear plant designs due to concerns due to a number of concerns. These could be summarized as cost, regulatory uncertainty, and a certain comfort factor with legacy analog technology. The replacement opportunity for these types of components represents a decision point for whether to invest in more modern technology that would provide superior operational and maintenance benefits. Yet, the application of digital technology has been problematic for the nuclear industry, due to qualification and regulatory issues. With some notable exceptions, the result has been a continuing reluctance to undertake the risks and uncertainties of implementing digital actuator technology when replacement opportunities present themselves. Rather, utilities would typically prefer to accept the performance limitations of the legacy analog actuator technologies to avoid impacts to project costs and schedules. The purpose of this report is to demonstrate that the benefits of digital actuator technology can be significant in terms of plant performance and that it is worthwhile to address the barriers currently holding back the widespread development and use of this technology. It addresses two important objectives in pursuit of the beneficial use of digital actuator technology for nuclear power plants: 1. To demonstrate the benefits of digital actuator
Land-surface modelling in hydrological perspective
Overgaard, Jesper; Rosbjerg, Dan; Butts, M.B.
2006-01-01
The purpose of this paper is to provide a review of the different types of energy-based land-surface models (LSMs) and discuss some of the new possibilities that will arise when energy-based LSMs are combined with distributed hydrological modelling. We choose to focus on energy-based approaches...... difficulties inherent in various evaluation procedures are presented. Finally, the dynamic coupling of hydrological and atmospheric models is explored, and the perspectives of such efforts are discussed......., because in comparison to the traditional potential evapotranspiration models, these approaches allow for a stronger link to remote sensing and atmospheric modelling. New opportunities for evaluation of distributed land-surface models through application of remote sensing are discussed in detail, and the...
Vibration analysis of magnetostrictive thin-film composite cantilever actuator
Xu, Yan; Shang, Xinchun
2016-09-01
The transverse vibration of a composed cantilever beam with magnetostrictive layer is analyzed, which is employed to simulate dynamic response of an actuator. The high-order shear deformation theory of beam and the coupling magnetoelastic constitutive relationship are introduced to construct the governing equations, all interface conditions between magnetostrictive film and elastic substrate as well as the free stress condition on the top and bottom surfaces of the beam can be satisfied. In order to demonstrate validity of the presented mathematical modeling, the verification examples are also given. Furthermore, the effect of geometry and material parameters on dynamic characteristics of magnetostrictive cantilever beam, such as the nature frequency and amplitude, is discussed. Moreover, through computing the magneto-mechanical coupling factor of the beam structure, the variation tendency curves of the factor along with different parameters and frequencies of magnetostrictive cantilever beam actuator have been presented. These numerical results should be useful for the design of beam-type with magnetostrictive thin-film actuators.
Lim, Sahng M.; Lee, Sangki; Park, Hoon C.; Yoon, Kwang J.; Goo, Nam Seo
2003-08-01
Biomimetic wing sections actuated by piezoceramics actuator LIPCA have been designed and their actuation displacements estimated by using the thermal analogy and MSC/NASTRAN based on the linear elasticity. The wing sections are fabricated as the design and tested for evaluation. Measured actuation displacements were larger than the estimated values mainly due to the material non-linearity of the PZT wafer. The biomimetic wing sections can be used for control surfaces of small scale UAVs.
NEW HYDRAULIC ACTUATOR'S POSITION SERVOCONTROL STRATEGY
KE Zunrong; ZHU Yuquan; LING Xuan
2007-01-01
A new hydraulic actuator-hydraulic muscle (HM) is described, and the actuator's features and applications are analyzed, then a position servocontrol system in which HM is main actuator is set up. The mathematical model of the system is built up and several control strategies are discussed. Based on the mathematical model, simulation research and experimental investigation with subsection PID control, neural network self-adaptive PID control and single neuron self-adaptive PID control adopted respectively are carried out, and the results indicate that compared with PID control, neural network self-adaptive PID control and single neuron self-adaptive PID control don't need controlled system's accurate model and have fast response, high control accuracy and strong robustness, they are very suitable for HM position servo control system.
Analysis and Prediction of the Thermal Performance of Piezoelectrically Actuated Fans
Acikalin, T.; Garimella, S V
2009-01-01
An experimentally validated numerical model is developed to analyze the operation of a piezoelectrically actuated cantilever vibrating close to a heated surface. The vibrating cantilever acts as a fan and provides localized cooling. The numerical results for the flow field and heat transfer show satisfactory agreement with experiments. The numerical model is used to develop fan curves for the piezoelectric fans, using a methodology similar to that used in constructing pump or fan curves for c...
Neelakantan, Vijay A.; Washington, Gregory N.; Bucknor, Norman K.
2005-05-01
High bandwidth actuation systems that are capable of simultaneously producing relatively large forces and displacements are required for use in automobiles and other industrial applications. Conventional hydraulic actuation mechanisms used in automotive brakes and clutches are complex, inefficient and have poor control robustness. These lead to reduced fuel economy, controllability issues and other disadvantages. This paper involves the design, development, testing and control of a two-stage hybrid actuation mechanism by combining classical actuators like DC motors and advanced smart material actuators like piezoelectric actuators. The paper also discusses the development of a robust control methodology using the Internal Model Control (IMC) principle and emphasizes the robustness property of this control methodology by comparing and studying simulation and experimental results.
A continuum method for modeling surface tension
Brackbill, J. U.; Kothe, D. B.; Zemach, C.
1992-01-01
In the novel method presented for modeling the effects of surface tension on fluid motion, the interfaces between fluids with different, color-represented properties are finite-thickness transition regions across which the color varies continuously. A force density proportional to the surface curvature of constant color is defined at each point in the transition region; this force-density is normalized in such a way that the conventional description of surface tension on an interface is recovered when the ratio of local transition-reion thickness to local curvature radius approaches zero. The properties of the method are illustrated by computational results for 2D flows.
Adaptive liquid lens driven by elastomer actuator
Jin, Boya; Lee, Ji-Hyeon; Zhou, Zuowei; Zhang, Guoqing; Lee, Gi-Bbeum; Ren, Hongwen; Nah, Changwoon
2016-01-01
When a liquid droplet is filled in the hole of a dielectric elastomer (DE) film, a liquid lens is prepared. By applying a DC voltage to the DE film, the liquid lens can be actuated. As a comparison, two liquid lenses, one in a millimeter scale and the other in a submillimeter scale, are demonstrated. In a relaxed state, the focal length of each liquid lens is the longest. In an actuated state, the diameter of each lens is reduced. As a result, their focal length is tuned. Here, the DE film functions as an actuator. Due to the biconvex shape and smooth liquid surface, each liquid lens can provide good optical performance. They also possess the merits of simple fabrication, compact structure, and easy operation. In contrast to the bigger liquid lens, the smaller one can present a better mechanical stability without the concern of the gravitational effect.
Larsen, Jeppe Veirum; Overholt, Daniel; Moeslund, Thomas B.
2013-01-01
Playing a guitar is normally only for people with fully functional hands. In this work we investigate alternative interaction concepts to enable or re-enable people with non-functional right hands or arms to play a guitar via actuated strumming. The functionality and complexity of right hand...... interaction with the guitar is immense. We therefore divided the right hand techniques into three main areas: Strumming, string picking / skipping, and string muting. This paper explores the first stage, strum- ming. We have developed an exploratory platform called the Actuated Guitar that utilizes a normal...
Low-Shock Pyrotechnic Actuator
Lucy, M. H.
1984-01-01
Miniature 1-ampere, 1-watt pyrotechnic actuator enclosed in flexible metal bellows. Bellows confines outgassing products, and pyrotechnic shock reduction achieved by action of bellows, gas cushion within device, and minimum use of pyrotechnic material. Actuator inexpensive, compact, and lightweight.
Applications of dielectric elastomer actuators
Pelrine, Ron; Sommer-Larsen, Peter; Kornbluh, Roy D.; Heydt, Richard; Kofod, Guggi; Pei, Qibing; Gravesen, Peter
2001-07-01
Dielectric elastomer actuators, based on the field-induced deformation of elastomeric polymers with compliant electrodes, can produce a large strain response, combined with a fast response time and high electromechanical efficiency. This unique performance, combined with other factors such as low cost, suggests many potential applications, a wide range of which are under investigation. Applications that effectively exploit the properties of dielectric elastomers include artificial muscle actuators for robots; low-cost, lightweight linear actuators; solid- state optical devices; diaphragm actuators for pumps and smart skins; acoustic actuators; and rotary motors. Issues that may ultimately determine the success or failure of the actuation technology for specific applications include the durability of the actuator, the performance of the actuator under load, operating voltage and power requirements, and electronic driving circuitry, to name a few.
In this study, an assessment is made for the helicopter vibration reduction of composite rotor blades using an active twist control concept. Special focus is given to the feasibility of implementing the benefits of the shear actuation mechanism along with elastic couplings of composite blades for achieving maximum vibration reduction. The governing equations of motion for composite rotor blades with surface bonded piezoceramic actuators are obtained using Hamilton's principle. The equations are then solved for dynamic response using finite element discretization in the spatial and time domains. A time domain unsteady aerodynamic theory with free wake model is used to obtain the airloads. A newly developed single-crystal piezoceramic material is introduced as an actuator material to exploit its superior shear actuation authority. Seven rotor blades with different elastic couplings representing stiffness properties similar to stiff-in-plane rotor blades are used to investigate the hub vibration characteristics. The rotor blades are modeled as a box beam with actuator layers bonded on the outer surface of the top and bottom of the box section. Numerical results show that a notable vibration reduction can be achieved for all the combinations of composite rotor blades. This investigation also brings out the effect of different elastic couplings on various vibration-reduction-related parameters which could be useful for the optimal design of composite helicopter blades
Pawar, Prashant M.; Jung, Sung Nam
2008-12-01
In this study, an assessment is made for the helicopter vibration reduction of composite rotor blades using an active twist control concept. Special focus is given to the feasibility of implementing the benefits of the shear actuation mechanism along with elastic couplings of composite blades for achieving maximum vibration reduction. The governing equations of motion for composite rotor blades with surface bonded piezoceramic actuators are obtained using Hamilton's principle. The equations are then solved for dynamic response using finite element discretization in the spatial and time domains. A time domain unsteady aerodynamic theory with free wake model is used to obtain the airloads. A newly developed single-crystal piezoceramic material is introduced as an actuator material to exploit its superior shear actuation authority. Seven rotor blades with different elastic couplings representing stiffness properties similar to stiff-in-plane rotor blades are used to investigate the hub vibration characteristics. The rotor blades are modeled as a box beam with actuator layers bonded on the outer surface of the top and bottom of the box section. Numerical results show that a notable vibration reduction can be achieved for all the combinations of composite rotor blades. This investigation also brings out the effect of different elastic couplings on various vibration-reduction-related parameters which could be useful for the optimal design of composite helicopter blades.
FLUTTER SUPPRESSION USING DISTRIBUTED PIEZOELECTRIC ACTUATORS
无
2000-01-01
The Flutter suppression using distributed piezoelectric actuators has been analyzed and tested. In constructing the finite element equation, effects of piezoelectric matrices are investigated. LQG method is used in designing the control law. In reducing the order of the control law, both balance realization and LK methods are used. For the rational approximation of the unsteady aerodynamic forces LS method is improved. In determining the piezoelectric constants d31 a new dynamic response method is developed. Laser vibrameter is used to pick up the model response and in ground resonance test the model is excited by piezoelectric actuators. Reasonable agreement of the wind tunnel flutter suppression test with calculated results is obtained.
Numerical simulation of mechatronic sensors and actuators
Kaltenbacher, Manfred
2007-01-01
Focuses on the physical modeling of mechatronic sensors and actuators and their precise numerical simulation using the Finite Element Method (FEM). This book discusses the physical modeling as well as numerical computation. It also gives a comprehensive introduction to finite elements, including their computer implementation.
Control of Adjustable Compliant Actuators
Berno J.E. Misgeld; Kurt Gerlach-Hahn; Daniel Rüschen; Anake Pomprapa; Steffen Leonhardt
2014-01-01
Adjustable compliance or variable stiffness actuators comprise an additional element to elastically decouple the actuator from the load and are increasingly applied to human-centered robotic systems. The advantages of such actuators are of paramount importance in rehabilitation robotics, where requirements demand safe interaction between the therapy system and the patient. Compliant actuator systems enable the minimization of large contact forces arising, for example, from muscular spasticity...
Felici, Federico
2012-10-01
Recent experiments on TCV have demonstrated integrated control of the sawtooth and Neoclassical Tearing Mode (NTM) instabilities in a combined preemption-suppression strategy. This strategy is enabled by new sawtooth control methods (sawtooth pacing) in which modulation of sawtooth-stabilizing electron cyclotron power during the sawtooth cycle stimulates the advent of the crash. Rather than controlling the average sawtooth period, the precise timing of each individual crash can now be prescribed. Using this knowledge, efficient preemptive stabilization of NTMs becomes possible by applying power on the rational surface only at the instant of the crash-generating seed island. TCV experiments demonstrate that this approach, reinforced by NTM stabilization as a backup strategy, is effectively failsafe. This opens the road to inductive H-mode scenarios with long sawteeth providing longer inter-crash periods of high density and temperature. Also Edge Localized Modes are susceptible to EC modulation and it is shown that individual ELM events can be controlled using similar techniques. For advanced tokamak scenarios, MHD control is to be combined with optimization and control of the plasma kinetic and magnetic profile evolution in time. Real-time simulation of a physical model (RAPTOR) of current transport, including bootstrap current, neoclassical conductivity and auxiliary current drive, yields complete knowledge of the relevant profiles at any given time. The pilot implementation on TCV shows that these calculations can indeed be done in real-time and the resulting profiles have been included in feedback control schemes. Integration of this model with time-varying equilibria and internal current profile diagnostics provides a new framework for real-time interpretation of diagnostic data for plasma prediction, scenario monitoring, disruption prevention and feedback control.
Performance evaluation of an improved fish robot actuated by piezoceramic actuators
Nguyen, Q. S.; Heo, S.; Park, H. C.; Byun, D.
2010-03-01
This paper presents an improved fish robot actuated by four lightweight piezocomposite actuators. Our newly developed actuation mechanism is simple to fabricate because it works without gears. With the new actuation mechanism, the fish robot has a 30% smaller cross section than our previous model. Performance tests of the fish robot in water were carried out to measure the tail-beat angle, the thrust force, the swimming speed for various tail-beat frequencies from 1 to 5 Hz and the turning radius at the optimal frequency. The maximum swimming speed of the fish robot is 7.7 cm s - 1 at a tail-beat frequency of 3.9 Hz. A turning experiment shows that the swimming direction of the fish robot can be controlled by changing the duty ratio of the driving voltage; the fish robot has a turning radius of 0.41 m for a left turn and 0.68 m for a right turn.
Performance evaluation of an improved fish robot actuated by piezoceramic actuators
This paper presents an improved fish robot actuated by four lightweight piezocomposite actuators. Our newly developed actuation mechanism is simple to fabricate because it works without gears. With the new actuation mechanism, the fish robot has a 30% smaller cross section than our previous model. Performance tests of the fish robot in water were carried out to measure the tail-beat angle, the thrust force, the swimming speed for various tail-beat frequencies from 1 to 5 Hz and the turning radius at the optimal frequency. The maximum swimming speed of the fish robot is 7.7 cm s−1 at a tail-beat frequency of 3.9 Hz. A turning experiment shows that the swimming direction of the fish robot can be controlled by changing the duty ratio of the driving voltage; the fish robot has a turning radius of 0.41 m for a left turn and 0.68 m for a right turn
Aerodynamic Optimization for Distributed Electro Mechanical Actuators Project
National Aeronautics and Space Administration — Traditional hydraulic actuation and control surface layout both limit span wise control of lift distribution, and require large volume within wing cross-section,...
Impact-Actuated Digging Tool for Lunar Excavation Project
National Aeronautics and Space Administration — Honeybee Robotics proposes to develop a vacuum compatible, impact-actuated digging tool for the excavation of frozen and compacted regolith on the lunar surface and...
Nonmagnetic driver for piezoelectric actuators
Ekhtiari, Marzieh
2014-01-01
Piezoelectric actuator drive aims to enable reliable motor performance in strong magnetic fields for magnetic res- onance imaging and computed tomography treatment tables. There are technical limitations in operation of these motors and drive systems related to magnetic interference. Piezoelectric...... actuators. Therefore, piezoelectric transformer-based power converters are used for driving piezoelectric actuator drive motor in the presence of high electromagnetic field....
Modeling of hydrogen desorption from tungsten surface
Hydrogen retention in metallic plasma-facing components is among key-issues for future fusion devices. For tungsten, which has been chosen as divertor material in ITER, hydrogen desorption parameters experimentally measured for fusion-related conditions show large discrepancies. In this paper, we therefore investigate hydrogen recombination and desorption on tungsten surfaces using molecular dynamics simulations and accelerated molecular dynamics simulations to analyze adsorption states, diffusion, hydrogen recombination into molecules, and clustering of hydrogen on tungsten surfaces. The quality of tungsten hydrogen interatomic potential is discussed in the light of MD simulations results, showing that three body interactions in current interatomic potential do not allow to reproduce hydrogen molecular recombination and desorption. Effects of surface hydrogen clustering on hydrogen desorption are analyzed by introducing a kinetic model describing the competition between surface diffusion, clustering and recombination. Different desorption regimes are identified and reproduce some aspects of desorption regimes experimentally observed
Modeling of hydrogen desorption from tungsten surface
Guterl, J., E-mail: jguterl@ucsd.edu [University of California, San Diego, La Jolla, CA 92093 (United States); Smirnov, R.D. [University of California, San Diego, La Jolla, CA 92093 (United States); Krasheninnikov, S.I. [University of California, San Diego, La Jolla, CA 92093 (United States); Nuclear Research National University MEPhI, Moscow 115409 (Russian Federation); Uberuaga, B.; Voter, A.F.; Perez, D. [Los Alamos National Laboratory, Los Alamos, NM 8754 (United States)
2015-08-15
Hydrogen retention in metallic plasma-facing components is among key-issues for future fusion devices. For tungsten, which has been chosen as divertor material in ITER, hydrogen desorption parameters experimentally measured for fusion-related conditions show large discrepancies. In this paper, we therefore investigate hydrogen recombination and desorption on tungsten surfaces using molecular dynamics simulations and accelerated molecular dynamics simulations to analyze adsorption states, diffusion, hydrogen recombination into molecules, and clustering of hydrogen on tungsten surfaces. The quality of tungsten hydrogen interatomic potential is discussed in the light of MD simulations results, showing that three body interactions in current interatomic potential do not allow to reproduce hydrogen molecular recombination and desorption. Effects of surface hydrogen clustering on hydrogen desorption are analyzed by introducing a kinetic model describing the competition between surface diffusion, clustering and recombination. Different desorption regimes are identified and reproduce some aspects of desorption regimes experimentally observed.
Derks, R.; Prins, M.W.J.; Wimberger-Friedl, R.
2006-01-01
Actuation principles of superparamagnetic beads applicable on biosensing (at single beads and chain orderning) are studied in this report. This research can be used to develop new techniques that are able to accelerate bio-assays. An experimental setup containing a sub-microliter fluid volume surrou
Baumbick, Robert J. (Inventor)
2002-01-01
The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.
Thermally Actuated Hydraulic Pumps
Jones, Jack; Ross, Ronald; Chao, Yi
2008-01-01
Thermally actuated hydraulic pumps have been proposed for diverse applications in which direct electrical or mechanical actuation is undesirable and the relative slowness of thermal actuation can be tolerated. The proposed pumps would not contain any sliding (wearing) parts in their compressors and, hence, could have long operational lifetimes. The basic principle of a pump according to the proposal is to utilize the thermal expansion and contraction of a wax or other phase-change material in contact with a hydraulic fluid in a rigid chamber. Heating the chamber and its contents from below to above the melting temperature of the phase-change material would cause the material to expand significantly, thus causing a substantial increase in hydraulic pressure and/or a substantial displacement of hydraulic fluid out of the chamber. Similarly, cooling the chamber and its contents from above to below the melting temperature of the phase-change material would cause the material to contract significantly, thus causing a substantial decrease in hydraulic pressure and/or a substantial displacement of hydraulic fluid into the chamber. The displacement of the hydraulic fluid could be used to drive a piston. The figure illustrates a simple example of a hydraulic jack driven by a thermally actuated hydraulic pump. The pump chamber would be a cylinder containing encapsulated wax pellets and containing radial fins to facilitate transfer of heat to and from the wax. The plastic encapsulation would serve as an oil/wax barrier and the remaining interior space could be filled with hydraulic oil. A filter would retain the encapsulated wax particles in the pump chamber while allowing the hydraulic oil to flow into and out of the chamber. In one important class of potential applications, thermally actuated hydraulic pumps, exploiting vertical ocean temperature gradients for heating and cooling as needed, would be used to vary hydraulic pressures to control buoyancy in undersea research
Minimal model for spoof acoustoelastic surface states
Christensen, Johan; Liang, Z.; Willatzen, Morten
2014-01-01
sound radiation in perfect rigid panels, we construct designer acoustoelastic surface waves that are entirely controlled by the geometrical environment. Comparisons to results obtained by full-wave simu- lations confirm the feasibility of the model and we demonstrate illustrative examples such as...
Surface tension in Kac glass models
In this paper we study a distance-dependent surface tension, defined as the free-energy cost for putting metastable states at a given distance. This will be done in the framework of a disordered microscopic model with Kac interactions that can be solved in the mean-field limit
Surface Tension in Kac Glass Models
Zarinelli, Elia; Franz, Silvio
2009-01-01
In this paper we study a distance-dependent surface tension, defined as the free-energy cost to put metastable states at a given distance. This will be done in the framework of a disordered microscopic model with Kac interactions that can be solved in the mean-field limit.
Global modelling of Cryptosporidium in surface water
Vermeulen, Lucie; Hofstra, Nynke
2016-04-01
Introduction Waterborne pathogens that cause diarrhoea, such as Cryptosporidium, pose a health risk all over the world. In many regions quantitative information on pathogens in surface water is unavailable. Our main objective is to model Cryptosporidium concentrations in surface waters worldwide. We present the GloWPa-Crypto model and use the model in a scenario analysis. A first exploration of global Cryptosporidium emissions to surface waters has been published by Hofstra et al. (2013). Further work has focused on modelling emissions of Cryptosporidium and Rotavirus to surface waters from human sources (Vermeulen et al 2015, Kiulia et al 2015). A global waterborne pathogen model can provide valuable insights by (1) providing quantitative information on pathogen levels in data-sparse regions, (2) identifying pathogen hotspots, (3) enabling future projections under global change scenarios and (4) supporting decision making. Material and Methods GloWPa-Crypto runs on a monthly time step and represents conditions for approximately the year 2010. The spatial resolution is a 0.5 x 0.5 degree latitude x longitude grid for the world. We use livestock maps (http://livestock.geo-wiki.org/) combined with literature estimates to calculate spatially explicit livestock Cryptosporidium emissions. For human Cryptosporidium emissions, we use UN population estimates, the WHO/UNICEF JMP sanitation country data and literature estimates of wastewater treatment. We combine our emissions model with a river routing model and data from the VIC hydrological model (http://vic.readthedocs.org/en/master/) to calculate concentrations in surface water. Cryptosporidium survival during transport depends on UV radiation and water temperature. We explore pathogen emissions and concentrations in 2050 with the new Shared Socio-economic Pathways (SSPs) 1 and 3. These scenarios describe plausible future trends in demographics, economic development and the degree of global integration. Results and
Development of microfabricated magnetic actuators for removing cellular occlusion
Here we report on the development of torsional magnetic microactuators for displacing biological materials in implantable catheters. Static and dynamic behaviors of the devices were characterized in air and in fluid using optical experimental methods. The devices were capable of achieving large deflections (>60°) and had resonant frequencies that ranged from 70 Hz to 1.5 kHz in fluid. The effect of long-term actuation (>2.5 × 108 cycles) was quantified using resonant shift as the metric (f < 2%). The cell-clearing capabilities of the devices were evaluated by examining the effect of actuation on a layer of aggressively growing adherent cells. On average, actuated microdevices removed 37.4% of the adherent cell layer grown over the actuator surface. The effects of actuation time, deflection angle and beam geometry were evaluated. The experimental results indicate that physical removal of adherent cells at the microscale is feasible using magnetic microactuation
Olkiluoto surface and near-surface hydrological modelling in 2010
The modeling approaches carried out with the Olkiluoto surface hydrological model (SHYD) include palaeohydrological evolution of the Olkiluoto Island, examination of the boundary condition at the geosphere-biosphere interface zone, simulations related to infiltration experiment, prediction of the influence of ONKALO on hydraulic head in shallow and deep bedrock and optimisation of the shallow monitoring network. A so called short-term prediction system was developed for continuous updating of the estimated drawdowns caused by ONKALO. The palaeohydrological simulations were computed for a period starting from the time when the highest hills on Olkiluoto Island rose above sea level around 2 500 years ago. The input data needed in the model were produced by the UNTAMO-toolbox. The groundwater flow evolution is primarily driven by the postglacial land uplift and the uncertainty in the land uplift model is the biggest single factor that influences the accuracy of the results. The consistency of the boundary condition at the geosphere-biosphere interface zone (GBIZ) was studied during 2010. The comparison carried out during 2010 showed that pressure head profiles computed with the SHYD model and deep groundwater flow model FEFTRA are in good agreement with each other in the uppermost 100 m of the bedrock. This implies that flux profiles computed with the two approaches are close to each other and hydraulic heads computed at level z=0 m with the SHYD can be used as head boundary condition in the deep groundwater flow model FEFTRA. The surface hydrological model was used to analyse the results of the infiltration experiment. Increase in bedrock recharge inside WCA explains around 60-63 % from the amount of water pumped from OL-KR14 and 37-40 % of the water pumped from OL-KR14 flows towards pumping section via the hydrogeological zones. Pumping from OL-KR14 has only a minor effect on heads and fluxes in zones HZ19A and HZ19C compared to responses caused by leakages into
Evolutionary flight and enabling smart actuator devices
Manzo, Justin; Garcia, Ephrahim
2007-04-01
Recent interest in morphing vehicles with multiple, optimized configurations has led to renewed research on biological flight. The flying vertebrates - birds, bats, and pterosaurs - all made or make use of various morphing devices to achieve lift to suit rapidly changing flight demands, including maneuvers as complex as perching and hovering. The first part of this paper will discuss these devices, with a focus on the morphing elements and structural strong suits of each creature. Modern flight correlations to these devices will be discussed and analyzed as valid adaptations of these evolutionary traits. The second part of the paper will focus on the use of active joint structures for use in morphing aircraft devices. Initial work on smart actuator devices focused on NASA Langley's Hyper-Elliptical Cambered Span (HECS) wing platform, which led to development of a discretized spanwise curvature effector. This mechanism uses shape memory alloy (SMA) as the sole morphing actuator, allowing fast rotation with lightweight components at the expense of energy inefficiency. Phase two of morphing actuator development will add an element of active rigidity to the morphing structure, in the form of shape memory polymer (SMP). Employing a composite structure of polymer and alloy, this joint will function as part of a biomimetic morphing actuator system in a more energetically efficient manner. The joint is thermally actuated to allow compliance on demand and rigidity in the nominal configuration. Analytical and experimental joint models are presented, and potential applications on a bat-wing aircraft structure are outlined.
Modeling aspects of the surface reconstruction problem
Toth, Charles K.; Melykuti, Gabor
1994-08-01
The ultimate goal of digital photogrammetry is to automatically produce digital maps which may in turn form the basis of GIS. Virtually all work in surface reconstruction deals with various kinds of approximations and constraints that are applied. In this paper we extend these concepts in various ways. For one, matching is performed in object space. Thus, matching and densification (modeling) is performed in the same reference system. Another extension concerns the solution of the second sub-problem. Rather than simply densifying (interpolating) the surface, we propose to model it. This combined top-down and bottom-up approach is performed in scale space, whereby the model is refined until compatibility between the data and expectations is reached. The paper focuses on the modeling aspects of the surface reconstruction problem. Obviously, the top-down and bottom-up model descriptions ought to be in a form which allows the generation and verification of hypotheses. Another crucial question is the degree of a priori scene knowledge necessary to constrain the solution space.
Finite element analysis of multilayer DEAP stack-actuators
Kuhring, Stefan; Uhlenbusch, Dominik; Hoffstadt, Thorben; Maas, Jürgen
2015-04-01
Dielectric elastomers (DE) are thin polymer films belonging to the class of electroactive polymers (EAP). They are coated with compliant and conductive electrodes on each side, which make them performing a relative high amount of deformation with considerable force generation under the influence of an electric field. Because the realization of high electric fields with a limited voltage level requests single layer polymer films to be very thin, novel multilayer actuators are utilized to increase the absolute displacement and force. In case of a multilayer stack-actuator, many actuator films are mechanically stacked in series and electrically connected in parallel. Because there are different ways to design such a stack-actuator, this contribution considers an optimization of some design parameters using the finite element analysis (FEA), whereby the behavior and the actuation of a multilayer dielectric electroactive polymer (DEAP) stack-actuator can be improved. To describe the material behavior, first different material models are compared and necessary material parameters are identified by experiments. Furthermore, a FEA model of a DEAP film is presented, which is expanded to a multilayer DEAP stack-actuator model. Finally, the results of the FEA are discussed and conclusions for design rules of optimized stack-actuators are outlined.
Work Functions for Models of Scandate Surfaces
Mueller, Wolfgang
1997-01-01
The electronic structure, surface dipole properties, and work functions of scandate surfaces have been investigated using the fully relativistic scattered-wave cluster approach. Three different types of model surfaces are considered: (1) a monolayer of Ba-Sc-O on W(100), (2) Ba or BaO adsorbed on Sc2O3 + W, and (3) BaO on SC2O3 + WO3. Changes in the work function due to Ba or BaO adsorption on the different surfaces are calculated by employing the depolarization model of interacting surface dipoles. The largest work function change and the lowest work function of 1.54 eV are obtained for Ba adsorbed on the Sc-O monolayer on W(100). The adsorption of Ba on Sc2O3 + W does not lead to a low work function, but the adsorption of BaO results in a work function of about 1.6-1.9 eV. BaO adsorbed on Sc2O3 + WO3, or scandium tungstates, may also lead to low work functions.
Gutfrind, Christophe; Dufour, Laurent; Liebart, Vincent; Vannier, Jean-Claude; Vidal, Pierre
2016-01-01
The purpose of this article is to describe the design of a limited stroke actuator and the corresponding prototype to drive a Low Pressure (LP) Exhaust Gas Recirculation (EGR) valve for use in Internal Combustion Engines (ICEs). The direct drive actuator topology is an axial flux machine with two air gaps in order to minimize the rotor inertia and a bipolar surface-mounted permanent magnet in order to respect an 80° angular stroke. Firstly, the actuator will be described and optimized under constraints of a 150 ms time response, a 0.363 N·m minimal torque on an angular range from 0° to 80° and prototyping constraints. Secondly, the finite element method (FEM) using the FLUX-3D(®) software (CEDRAT, Meylan, France) will be used to check the actuator performances with consideration of the nonlinear effect of the iron material. Thirdly, a prototype will be made and characterized to compare its measurement results with the analytical model and the FEM model results. With these electromechanical behavior measurements, a numerical model is created with Simulink(®) in order to simulate an EGR system with this direct drive actuator under all operating conditions. Last but not least, the energy consumption of this machine will be estimated to evaluate the efficiency of the proposed EGR electromechanical system. PMID:27213398
Dielectric Actuation of Polymers
Niu, Xiaofan
Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy densities, high coupling efficiency, quiet operation, and light weight. One focus of this dissertation is on the design of DE materials with high performance and easy processing. UV radiation curing of reactive species is studied as a generic synthesis methodology to provide a platform for material scientists to customize their own DE materials. Oligomers/monomers, crosslinkers, and other additives are mixed and cured at appropriate ratios to control the stress-strain response, suppress electromechanical instability of the resulting polymers, and provide stable actuation strains larger than 100% and energy densities higher than 1 J/g. The processing is largely simplified in the new material system by removal of the prestretching step. Multilayer stack actuators with 11% linear strain are demonstrated in a procedure fully compatible with industrial production. A multifunctional DE derivative material, bistable electroactive polymer (BSEP), is invented enabling repeatable rigid-to-rigid deformation without bulky external structures. Bistable actuation allows the polymer actuator to have two distinct states that can support external load without device failure. Plasticizers are used to lower the glass transition temperature to 45 °C. Interpenetrating polymer network structure is established inside the BSEP to suppress electromechanical instability, providing a breakdown field of 194 MV/m and a stable bistable strain as large as 228% with a 97% strain fixity. The application of BSEP
Time series modelling of surface pressure data
Al-Awadhi, Shafeeqah; Jolliffe, Ian
1998-03-01
In this paper we examine time series modelling of surface pressure data, as measured by a barograph, at Herne Bay, England, during the years 1981-1989. Autoregressive moving average (ARMA) models have been popular in many fields over the past 20 years, although applications in climatology have been rather less widespread than in some disciplines. Some recent examples are Milionis and Davies (Int. J. Climatol., 14, 569-579) and Seleshi et al. (Int. J. Climatol., 14, 911-923). We fit standard ARMA models to the pressure data separately for each of six 2-month natural seasons. Differences between the best fitting models for different seasons are discussed. Barograph data are recorded continuously, whereas ARMA models are fitted to discretely recorded data. The effect of different spacings between the fitted data on the models chosen is discussed briefly.Often, ARMA models can give a parsimonious and interpretable representation of a time series, but for many series the assumptions underlying such models are not fully satisfied, and more complex models may be considered. A specific feature of surface pressure data in the UK is that its behaviour is different at high and at low pressures: day-to-day changes are typically larger at low pressure levels than at higher levels. This means that standard assumptions used in fitting ARMA models are not valid, and two ways of overcoming this problem are investigated. Transformation of the data to better satisfy the usual assumptions is considered, as is the use of non-linear, specifically threshold autoregressive (TAR), models.
Failure of cargo aileron’s actuator
G. Zucca
2014-10-01
Full Text Available During a ferry flight, in a standard operation condition and at cruising level, a military cargo experienced a double hydraulic system failure due to a structural damage of the dual booster actuator. The booster actuator is the main component in mechanism of aileron’s deflection. The crew was able to arrange an emergency landing thanks to the spare oil onboard: load specialists refilled the hydraulic reservoirs. Due to safety concerns and in order to prevent the possibility of other similar incidents, a technical investigation took place. The study aimed to carry out the analysis of root causes of the actuator failure. The Booster actuator is composed mainly by the piston rod and its aluminum external case (AA7049. The assembly has two bronze caps on both ends. These are fixed in position by means of two retainers. At one end of the actuator case is placed a trunnion: a cylindrical protrusion used as a pivoting point on the aircraft. The fracture was located at one end of the case, on the trunnion side, in correspondence to the cap and over the retainer. One of the two fracture surfaces was found separated to the case and with the cap entangled inside. The fracture surfaces of the external case indicated fatigue crack growth followed by ductile separation. The failure analysis was performed by means of optical, metallographic, digital and electronic microscopy. The collected evidences showed a multiple initiation fracture mechanism. Moreover, 3D scanner reconstruction and numerical simulation demonstrated that dimensional non conformances and thermal loads caused an abnormal stress concentration. Stress concentration was located along the case assy outer surface where the fatigue crack originated. The progressive rupture mechanism grew under cyclical axial load due to the normal operations. Recommendations were issued in order to improve dimensional controls and assembly procedures during production and overhaul activities.
Integration of Heterogenous Digital Surface Models
Boesch, R.; Ginzler, C.
2011-08-01
The application of extended digital surface models often reveals, that despite an acceptable global accuracy for a given dataset, the local accuracy of the model can vary in a wide range. For high resolution applications which cover the spatial extent of a whole country, this can be a major drawback. Within the Swiss National Forest Inventory (NFI), two digital surface models are available, one derived from LiDAR point data and the other from aerial images. Automatic photogrammetric image matching with ADS80 aerial infrared images with 25cm and 50cm resolution is used to generate a surface model (ADS-DSM) with 1m resolution covering whole switzerland (approx. 41000 km2). The spatially corresponding LiDAR dataset has a global point density of 0.5 points per m2 and is mainly used in applications as interpolated grid with 2m resolution (LiDAR-DSM). Although both surface models seem to offer a comparable accuracy from a global view, local analysis shows significant differences. Both datasets have been acquired over several years. Concerning LiDAR-DSM, different flight patterns and inconsistent quality control result in a significantly varying point density. The image acquisition of the ADS-DSM is also stretched over several years and the model generation is hampered by clouds, varying illumination and shadow effects. Nevertheless many classification and feature extraction applications requiring high resolution data depend on the local accuracy of the used surface model, therefore precise knowledge of the local data quality is essential. The commercial photogrammetric software NGATE (part of SOCET SET) generates the image based surface model (ADS-DSM) and delivers also a map with figures of merit (FOM) of the matching process for each calculated height pixel. The FOM-map contains matching codes like high slope, excessive shift or low correlation. For the generation of the LiDAR-DSM only first- and last-pulse data was available. Therefore only the point distribution can
Modelling Ocean Surface Waves in Polar Regions
Hosekova, Lucia; Aksenov, Yevgeny; Coward, Andrew; Bertino, Laurent; Williams, Timothy; Nurser, George A. J.
2015-04-01
In the Polar Oceans, the surface ocean waves break up sea ice cover and create the Marginal Ice Zone (MIZ), an area between the sea-ice free ocean and pack ice characterized by highly fragmented ice. This band of sea ice cover is undergoing dramatic changes due to sea ice retreat, with up to a 39% widening in the Arctic Ocean reported over the last three decades and projections predicting a continuing increase. The surface waves, sea ice and ocean interact in the MIZ through multiple complex feedbacks and processes which are not accounted for in any of the present-day climate models. To address this issue, we present a model development which implements surface ocean wave effects in the global Ocean General Circulation Model NEMO, coupled to the CICE sea ice model. Our implementation takes into account a number of physical processes specific to the MIZ dynamics. Incoming surface waves are attenuated due to reflection and energy dissipation induced by the presence of ice cover, which is in turn fragmented in response to external stresses. This process generates a distribution of floe sizes and impacts the dynamics of sea ice by the means of combined rheology that takes into account floe collisions and allows for a more realistic representation of the MIZ. We present results from the NEMO OGCM at 1 degree resolution with a wave-ice interaction module described above. The module introduces two new diagnostics previously unavailable in GCM's: surface wave spectra in sea ice covered areas, and floe size distribution due to wave-induced fragmentation. We discuss the impact of these processes on the ocean and sea ice state, including ocean circulation, mixing, stratification and the role of the MIZ in the ocean variability. The model predictions for the floe sizes in the summer Arctic Ocean range from 60 m in the inner MIZ to a few tens of meters near the open ocean, which agrees with estimates from the satellites. The extent of the MIZ throughout the year is also in
Aagaard Madsen, Helge; Larsen, Torben J.; Schmidt Paulsen, Uwe; Vita, Luca
2013-01-01
of VAWTs for floating MW concepts. The AC model is a 2D flow model and has thus some advantages compared with the stream tube models often used in VAWT aerodynamic and aeroelastic simulation models. A major finding presented in the present paper is a simple way to correct the results from the linear...
Experimental Investigation of the Effect of the Driving Voltage of an Electroadhesion Actuator
Keng Huat Koh
2014-06-01
Full Text Available This paper investigates the effect of driving voltage on the attachment force of an electroadhesion actuator, as the existing literature on the saturation of the adhesive force at a higher electric field is incomplete. A new type of electroadhesion actuator using normally available materials, such as aluminum foil, PVC tape and a silicone rubber sheet used for keyboard protection, has been developed with a simple layered structure that is capable of developing adhesive force consistently. The developed actuator is subjected to the experiment for the evaluation of various test surfaces; aluminum, brick, ceramic, concrete and glass. The driving high voltage is varied in steps to determine the characteristics of the output holding force. Results show a quadratic relation between F (adhesion force and V (driving voltage within the 2 kV range. After this range, the F-V responses consistently show a saturation trend at high electric fields. Next, the concept of the leakage current that can occur in the dielectric material and the corona discharge through air has been introduced. Results show that the voltage level, which corresponds to the beginning of the supply current, matches well with the beginning of the force saturation. With the confirmation of this hypothesis, a working model for electroadhesion actuation is proposed. Based on the experimental results, it is proposed that such a kind of actuator can be driven within a range of optimum high voltage to remain electrically efficient. This practice is recommended for the future design, development and characterization of electroadhesion actuators for robotic applications.
Improving land surface models with FLUXNET data
M. Williams
2009-03-01
Full Text Available There is a growing consensus that land surface models (LSMs that simulate terrestrial biosphere exchanges of matter and energy must be better constrained with data to quantify and address their uncertainties. FLUXNET, an international network of sites that measure the land surface exchanges of carbon, water and energy using the eddy covariance technique, is a prime source of data for model improvement. Here we outline a multi-stage process for fusing LSMs with FLUXNET data to generate better models with quantifiable uncertainty. First, we describe FLUXNET data availability, and its random and systematic biases. We then introduce methods for assessing LSM model runs against FLUXNET observations in temporal and spatial domains. These assessments are a prelude to more formal model-data fusion (MDF. MDF links model to data, based on error weightings. In theory, MDF produces optimal analyses of the modelled system, but there are practical problems. We first discuss how to set model errors and initial conditions. In both cases incorrect assumptions will affect the outcome of the MDF. We then review the problem of equifinality, whereby multiple combinations of parameters can produce similar model output. Fusing multiple independent data provides a means to limit equifinality. We then show how parameter probability density functions (PDFs from MDF can be used to interpret model process validity, and to propagate errors into model outputs. Posterior parameter distributions are a useful way to assess the success of MDF, combined with a determination of whether model residuals are Gaussian. If the MDF scheme provides evidence for temporal variation in parameters, then that is indicative of a critical missing dynamic process. A comparison of parameter PDFs generated with the same model from multiple FLUXNET sites can provide insights into the concept and validity of plant functional types (PFT – we would expect similar parameter estimates among sites
Improving land surface models with FLUXNET data
Y. -P. Wang
2009-07-01
Full Text Available There is a growing consensus that land surface models (LSMs that simulate terrestrial biosphere exchanges of matter and energy must be better constrained with data to quantify and address their uncertainties. FLUXNET, an international network of sites that measure the land surface exchanges of carbon, water and energy using the eddy covariance technique, is a prime source of data for model improvement. Here we outline a multi-stage process for "fusing" (i.e. linking LSMs with FLUXNET data to generate better models with quantifiable uncertainty. First, we describe FLUXNET data availability, and its random and systematic biases. We then introduce methods for assessing LSM model runs against FLUXNET observations in temporal and spatial domains. These assessments are a prelude to more formal model-data fusion (MDF. MDF links model to data, based on error weightings. In theory, MDF produces optimal analyses of the modelled system, but there are practical problems. We first discuss how to set model errors and initial conditions. In both cases incorrect assumptions will affect the outcome of the MDF. We then review the problem of equifinality, whereby multiple combinations of parameters can produce similar model output. Fusing multiple independent and orthogonal data provides a means to limit equifinality. We then show how parameter probability density functions (PDFs from MDF can be used to interpret model validity, and to propagate errors into model outputs. Posterior parameter distributions are a useful way to assess the success of MDF, combined with a determination of whether model residuals are Gaussian. If the MDF scheme provides evidence for temporal variation in parameters, then that is indicative of a critical missing dynamic process. A comparison of parameter PDFs generated with the same model from multiple FLUXNET sites can provide insights into the concept and validity of plant functional types (PFT – we would expect similar parameter
Optimal actuator placement on an active reflector using a modified simulated annealing technique
Kuo, Chin-Po; Bruno, Robin
1991-01-01
The development of a lightweight actuation system for maintaining the surface accuracy of a composite honeycomb panel using piezoelectric actuators is discussed. A modified simulated annealing technique is used to optimize the problem with both combinatorial and continuous criteria and with inequality constraints. Near optimal solutions for the location of the actuators, using combinatorial optimization, and for the required actuator forces, employing continuous optimization, are sought by means of the modified simulated annealing technique. The actuator locations are determined by first seeking a near optimum solution using the modified simulated annealing technique. The final actuator configuration consists of an arrangement wherein the piezoelectric actuators are placed along six radial lines. Numerical results showing the achievable surface correction by means of this configuration are presented.
Automatic rotary valve actuator
This report describes the design, construction, and operation of a microcomputer-controlled valve actuator for operating test valves requiring rotary motion of the valve stem. An AIM 65 microcomputer, using a FORTH language program, controls an air motor and air clutch mounted within an oven to accomplish testing at elevated temperatures. The valve actuator closes the test valve until a preset torque is reached and then opens the valve to its initial starting point. The number of cycles and extremes of rotation are tallied and printed as the test progresses. Provisions are made to accept remote signals to stop the test and to indicate to a remote device when the test has been stopped
Thermally actuated linkage arrangement
A reusable thermally actuated linkage arrangement includes a first link member having a longitudinal bore therein adapted to receive at least a portion of a second link member therein, the first and second members being sized to effect an interference fit preventing relative movement there-between at a temperature below a predetermined temperature. The link members have different coefficients of thermal expansion so that when the linkage is selectively heated by heating element to a temperature above the predetermined temperature, relative longitudinal and/or rotational movement between the first and second link members is enabled. Two embodiments of a thermally activated linkage are disclosed which find particular application in actuators for a grapple head positioning arm in a nuclear reactor fuel handling mechanism to facilitate back-up safety retraction of the grapple head independently from the primary fuel handling mechanism drive system. (author)
Modeling of ESD events from polymeric surfaces
Pfeifer, Kent Bryant
2014-03-01
Transient electrostatic discharge (ESD) events are studied to assemble a predictive model of discharge from polymer surfaces. An analog circuit simulation is produced and its response is compared to various literature sources to explore its capabilities and limitations. Results suggest that polymer ESD events can be predicted to within an order of magnitude. These results compare well to empirical findings from other sources having similar reproducibility.
Xavier Arouette
2010-03-01
Full Text Available We have developed a hydraulic displacement amplification mechanism (HDAM and studied its dynamic response when combined with a piezoelectric actuator. The HDAM consists of an incompressible fluid sealed in a microcavity by two largely deformable polydimethylsiloxane (PDMS membranes. The geometry with input and output surfaces having different cross-sectional areas creates amplification. By combining the HDAM with micro-actuators, we can amplify the input displacement generated by the actuators, which is useful for applications requiring large deformation, such as tactile displays. We achieved a mechanism offering up to 18-fold displacement amplification for static actuation and 12-fold for 55 Hz dynamic actuation.
National Aeronautics and Space Administration — Model-based diagnosis typically uses analytical redundancy to compare predictions from a model against observations from the system being diagnosed. However this...
Janko, Balazs
2015-01-01
Industrial robotic manipulators can be found in most factories today. Their tasks are accomplished through actively moving, placing and assembling parts. This movement is facilitated by actuators that apply a torque in response to a command signal. The presence of friction and possibly backlash have instigated the development of sophisticated compensation and control methods in order to achieve the desired performance may that be accurate motion tracking, fast movement or in fa...
Valve actuator motor degradation
Valve actuator motor degradation and failure has been a significant, but little studied, problem in the nuclear industry. This study provides a discussion of the primary failure mode --thermal degradation-- and reviews the basis for the solution to thermal degradation -- thermal protection. The study also provides reviews of various industry data bases, discusses effects of other failure modes such as corrosion, and provides a review of other considerations the user should entertain when assessing thermal protection
Stepper Motor Actuated Microvalve
Fazal, Imran; Louwerse, Marcus; Jansen, Henri; Elwenspoek, Miko
2006-01-01
We present the design, fabrication and characterization of a novel microvalve realized by combining micro and fine machining techniques. The design is for high flow rates at high pressure difference between inlet and outlet, burst pressure of up to 15 bars, there is no power consumption required for the valve to maintain its position during operation in any intermediate state and the process gas does not interact with the actuation mechanism. The microvalve was experimentally characterized wi...
Metal hydride actuation device
A self-recocking actuation device is disclosed. One possible use for it is in conjunction with a pneumatic fire protection system. This invention employs the process known as occlusion to store large amounts of gas in a small volume. Metal hydrides in a chamber are used to store hydrogen in the disclosed preferred embodiment. Upon the application of heat-from a heat source like a resistance heater-the charged metal hydride releases its hydrogen (H2) in a chamber having only one exit opening which empties into a sealed bellows. This bellows contacts a piston located in another chamber wherein a biased resetting spring is provided to normally maintain the piston in contact with the bellows. As the pressure from the H2 gas builds up, it overcomes the biased spring to move it and the piston along with an associated pin or other actuator. If used to actuate a pneumatic fire protection system, the pin or actuator at the downward side of its stroke in turn, may puncture a shearable diaphragm or in some other way releases the contents of a container containing a second gas, like nitrogen (N2), which is then released from a second exit port in a different chamber to charge the fire protection system. Recocking of the piston begins as the heating of the metal hydride ceases. As cooling takes place the hydrogen is absorbed to reenter the hydride to decrease the gas pressure supplied. The piston's biased resetting spring then recocks the piston to its original position
Improvements on Mean Free Wave Surface Modeling
董国海; 滕斌; 程亮
2002-01-01
Some new results of the modeling of mean free surface of waves or wave set-up are presented. The stream function wave theory is applied to incident short waves. The limiting wave steepness is adopted as the wave breaker index in the calculation of wave breaking dissipation. The model is based on Roelvink (1993), but the numerical techniques used in the solution are based on the Weighted-Average Flux (WAF) method (Watson et al., 1992), with Time-Operator-Splitting (TOS) used for the treatment of the source terms. This method allows a small number of computational points to be used, and is particularly efficient in modeling wave set-up. The short wave (or incident primary wave) energy equation issolved by use of a traditional Lax-Wendroff technique. The present model is found to be satisfactory compared with the measurements conducted by Stive (1983).
Piezoelectric stack actuator parameter extraction with hysteresis compensation
Zsurzsan, Tiberiu-Gabriel; Mangeot, Charles; Andersen, Michael A. E.;
2014-01-01
The Piezoelectric Actuator Drive (PAD) is a type of rotary motor that transforms the linear motion of piezoelectric stack actuators into a precise rotational motion. The very high stiffness of the actuators employed make this type of motor suited for open-loop control, but the inherent hysteresis...... exhibited by piezoelectric ceramics causes losses. Therefore, this paper presents a straightforward method to measure piezoelectric stack actuator equiv- alent parameters that includes nonlinearities. By folding the nonlinearities into a newly-defined cou- pling coefficient, the inherent hysteretic behavior...... of piezoelectric stack actuators can be greatly reduced through precompensation. Experimental results show a fitting accuracy of 98.8 % between the model and measurements and a peak absolute error reduction by a factor of 10 compared to the manufacturer- provided parameter. This method improves both the static...
OPTIMIZATION OF MOVING COIL ACTUATORS FOR DIGITAL DISPLACEMENT MACHINES
Nørgård, Christian; Bech, Michael Møller; Roemer, Daniel Beck;
actuating annular seat valves in a digital displacement machine. The optimization objectives are to the minimize the actuator power, the valve flow losses and the height of the actuator. Evaluation of the objective function involves static finite element simulation and simulation of an entire operation...... cycle using a single chamber Digital Displacement lumped parameter model. The optimization results shows that efficient operation is achievable using all of the proposed moving coil geometries, however some geometries require more space and actuator power. The most appealing of the optimized actuator...... designs requires approximately 20 W on average and may be realized in 20 mm Ø 22.5 mm (height diameter) for a 20 kW pressure chamber. The optimization is carried out using the multi-objective Generalized Differential Evolution optimization algorithm GDE3 which successfully handles constrained multi...
Asymmetric Bellow Flexible Pneumatic Actuator for Miniature Robotic Soft Gripper
Ganesha Udupa
2014-01-01
Full Text Available The necessity of the soft gripping devices is increasing day-by-day in medical robotics especially when safe, gentle motions and soft touch are necessary. In this paper, a novel asymmetric bellow flexible pneumatic actuator (AFPA has been designed and fabricated to construct a miniaturised soft gripper that could be used to grip small objects. The model of AFPA is designed using solid works and its bending motion is simulated in Abaqus software for optimisation and compared with experimental results. The actuator is fabricated using compression molding process that includes micromachining of the molds. Experiments conducted show the bending characteristics of the actuator at different pressures. The actuator shows excellent bending performance and the eccentricity in its design supports increased bending or curling motion up to a certain extent compared to normal bellows without eccentricity. The effects of profile shape and eccentricity on the actuator performance are analysed and the results are presented.
Barton, J. E.; Boyer, M. D.; Shi, W.; Wehner, W. P.; Schuster, E.; Ferron, J. R.; Walker, M. L.; Humphreys, D. A.; Luce, T. C.; Turco, F.; Penaflor, B. G.; Johnson, R. D.
2015-09-01
DIII-D experimental results are reported to demonstrate the potential of physics-model-based safety factor profile control for robust and reproducible sustainment of advanced scenarios. In the absence of feedback control, variability in wall conditions and plasma impurities, as well as drifts due to external disturbances, can limit the reproducibility of discharges with simple pre-programmed scenario trajectories. The control architecture utilized is a feedforward + feedback scheme where the feedforward commands are computed off-line and the feedback commands are computed on-line. In this work, a first-principles-driven (FPD), physics-based model of the q profile and normalized beta ({β\\text{N}} ) dynamics is first embedded into a numerical optimization algorithm to design feedforward actuator trajectories that steer the plasma through the tokamak operating space to reach a desired stationary target state that is characterized by the achieved q profile and {β\\text{N}} . Good agreement between experimental results and simulations demonstrates the accuracy of the models employed for physics-model-based control design. Second, a feedback algorithm for q profile control is designed following an FPD approach, and the ability of the controller to achieve and maintain a target q profile evolution is tested in DIII-D high confinement (H-mode) experiments. The controller is shown to be able to effectively control the q profile when {β\\text{N}} is relatively close to the target, indicating the need for integrated q profile and {β\\text{N}} control to further enhance the ability to achieve robust scenario execution. The ability of an integrated q profile + {β\\text{N}} feedback controller to track a desired target is demonstrated through simulation.
Experimental investigation of the deformable mirror with bidirectional thermal actuators.
Huang, Lei; Ma, Xingkun; Gong, Mali; Bian, Qi
2015-06-29
A deformable mirror with actuators of thermoelectric coolers (TECs) is introduced in this paper. Due to the bidirectional thermal actuation property of the TEC, both upward and downward surface control is available for the DM. The response functions of the actuators are investigated. A close-loop wavefront control experiment is performed too, where the defocus and the astigmatism were corrected. The results reveal that there is a promising prospect for the novel design to be used in corrections of static aberrations, such as in the Inertial Confinement Fusion (ICF). PMID:26191759
Liquid surface model for carbon nanotube energetics
Solov'yov, Ilia; Mathew, Maneesh; Solov'yov, Andrey V.;
2008-01-01
In the present paper we developed a model for calculating the energy of single-wall carbon nanotubes of arbitrary chirality. This model, which we call as the liquid surface model, predicts the energy of a nanotube with relative error less than 1% once its chirality and the total number of atoms are...... an important insight in the energetics and stability of nanotubes of different chirality and might be important for the understanding of nanotube growth process. For the computations we use empirical Brenner and Tersoff potentials and discuss their applicability to the study of carbon nanotubes. From...... the calculated energies we determine the elastic properties of the single-wall carbon nanotubes (Young modulus, curvature constant) and perform a comparison with available experimental measurements and earlier theoretical predictions....
Topological design of compliant smart structures with embedded movable actuators
In the optimal configuration design of piezoelectric smart structures, it is favorable to use actuation elements with certain predefined geometries from the viewpoint of manufacturability of fragile piezoelectric ceramics in practical applications. However, preserving the exact shape of these embedded actuators and tracking their dynamic motions presents a more challenging research task than merely allowing them to take arbitrary shapes. This paper proposes an integrated topology optimization method for the systematic design of compliant smart structures with embedded movable PZT (lead zirconate titanate) actuators. Compared with most existing studies, which either optimize positions/sizes of the actuators in a given host structure or design the host structure with pre-determined actuator locations, the proposed method simultaneously optimizes the positions of the movable PZT actuators and the topology of the host structure, typically a compliant mechanism for amplifying the small strain stroke. A combined topological description model is employed in the optimization, where the level set model is used to track the movements of the PZT actuators and the independent point-wise density interpolation (iPDI) approach is utilized to search for the optimal topology of the host structure. Furthermore, we define an integral-type constraint function to prevent overlaps between the PZT actuators and between the actuators and the external boundaries of the design domain. Such a constraint provides a unified and explicit mathematical statement of the non-overlap condition for any number of arbitrarily shaped embedded actuators. Several numerical examples are used to demonstrate the effectiveness of the proposed optimization method. (paper)
Research on giant magnetostrictive micro-displacement actuator with self-adaptive control algorithm
Giant magnetostrictive micro-displacement actuator has some unique characteristics, such as big output torque and high precision localization which can be in the nanometer scale. Because the relation between input magnetic field and output strain of giant magnetostrictive micro-displacement actuator exhibits hysteresis and eddy flow, the actuator has to be controlled and used in low input frequency mode or in static mode. When the actuator is controlled with a high input frequency (above 100 Hz), the output strain will exhibit strong nonlinearity. This paper found hysteresis and nonlinearity dynamic transfer function of the actuator based on Jiles-Atherton hysteresis model. The output strain of Jiles-Atherton hystersis model can reflect real output of actuator corresponding to the real input magnetic field, and this has been verified by experiment. Against the nonlinearity generated by hysteresis and eddy flow in this paper, the output strain of actuator is used for feedback to control system, and the control system adopted self-adaptive control algorithm, the ideal input and output model of actuator is used for a reference model and a hysteresis transfer function for the actuator real model. Through experiment, it has been verified that this algorithm can improve the dynamic frequency of the giant magnetostrictive micro-displacement actuator and guarantee high precision localization and linearity between the input magnetic field and output strain of the actuator at the same time
Experimental study on the use of synthetic jet actuators for lift control
Torres, Ricardo Benjamin
An experimental study on the use of synthetic jet actuators for lift control is conducted. The synthetic jet actuator is placed on the pressure side towards the trailing edge on a NACA 65(2)-415 airfoil representative of the cross section of an Inlet Guide Vane (IGV) in an industrial gas compressor. By redirecting or vectoring the shear layer at the trailing edge, the synthetic jet actuator increases lift and decreases drag on the airfoil without a mechanical device or flap. A compressor map that defines upper and lower bounds on operating velocities and airfoil dimensions, is compared with operating conditions of the low-speed wind tunnel at San Diego State University, to match gas compressor conditions in the wind tunnel. Realistic test conditions can range from Mach=0.12 to Mach= 0.27 and an airfoil chord from c=0.1 m to c=0.3 m. Based on the operating conditions, a final airfoil model is fabricated with a chord of c=0.1m. Several synthetic jet actuator designs are considered. A initial synthetic jet is designed to house a piezoelectric element with a material frequency of 1200 hz in a cavity with a volume of 4.47 cm3, a slot width of 0.25 mm, and a slot depth of 1.5 mm. With these dimensions, the Helmholtz frequency of the design is 1800Hz. Particle Image Velocimetry (PIV) experiments show that the design has a jet with a peak centerline jet velocity of 26 m/s at 750 Hz. A modified slant face synthetic jet is designed so that the cavity fits flush within the NACA airfoil surface. The slanted synthetic jet has a cavity volume of 4.67 cm3, a slot width of 0.25 mm, and a slot depth of 3.45 mm resulting in a Helmholtz frequency of 1170 hz for this design. PIV experiments show that the jet is redirected along the slant face according to the Coanda effect. A final synthetic jet actuator is directly integrated into the trailing edge of an airfoil with a cavity volume of 4.6 cm3, a slot width of 0.2 mm, and a slot depth of 1.6 mm. The Helmholtz frequency is 1450 Hz and
Continuum Surface Energy from a Lattice Model
Rosakis, Phoebus
2012-01-01
The energy of a homogeneously deformed, faceted crystal is calculated in the context of a central force lattice model in two dimensions. It is shown that the energy equals the bulk elastic energy, plus the integral over the boundary of a surface energy density, plus the sum over the vertices of a corner energy function. This is an exact result when the interatomic potential has finite range; for an infinite-range potential it is asymptotically valid as the lattice parameter tends to zero. The surface energy density is obtained explicitly as a function of the deformation gradient and boundary normal. The corner energy is found as an explicit function of the deformation gradient and the normals of the two facets meeting at the corner. A new bond counting approach is used, which allows the problem to be reduced to the well known lattice point problem of number theory.
Direct computations of a synthetic jet actuator
Hayes-McCoy, Declan
2012-01-01
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. Synthetic jet actuators have previously been defined as having potential use in both internal and external aerodynamic applications. The formation of a jet flow perpendicular to the surface of an aerofoil or in a duct of diffuser has a range of potential flow control benefits. These benefits can include both laminar to turbulent transition control, which is associated with a drag reduction in...
Modeling of surface myoelectric signals--Part I: Model implementation.
Merletti, R; Lo Conte, L; Avignone, E; Guglielminotti, P
1999-07-01
The relationships between the parameters of active motor units (MU's) and the features of surface electromyography (EMG) signals have been investigated using a mathematical model that represents the surface EMG as a summation of contributions from the single muscle fibers. Each MU has parallel fibers uniformly scattered within a cylindrical volume of specified radius embedded in an anisotropic medium. Two action potentials, each modeled as a current tripole, are generated at the neuromuscular junction, propagate in opposite directions and extinguish at the fiber-tendon endings. The neuromuscular junctions and fiber-tendon endings are uniformly scattered within regions of specified width. Muscle fiber conduction velocity and average fiber length to the right and left of the center of the innervation zone are also specified. The signal produced by MU's with different geometries and conduction velocities are superimposed. Monopolar, single differential and double differential signals are computed from electrodes placed in equally spaced locations on the surface of the muscle and are displayed as functions of any of the model's parameters. Spectral and amplitude variables and conduction velocity are estimated from the surface signals and displayed as functions of any of the model's parameters. The influence of fiber-end effects, electrode misalignment, tissue anisotropy, MU's location and geometry are discussed. Part II of this paper will focus on the simulation and interpretation of experimental signals. PMID:10396899
Miniaturized Rotary Actuators Using Shape Memory Alloy for Insect-Type MEMS Microrobot
Ken Saito
2016-03-01
Full Text Available Although several types of locomotive microrobots have been developed, most of them have difficulty locomoting on uneven surfaces. Thus, we have been focused on microrobots that can locomote using step patterns. We are studying insect-type microrobot systems. The locomotion of the microrobot is generated by rotational movements of the shape memory alloy-type rotary actuator. In addition, we have constructed artificial neural networks by using analog integrated circuit (IC technology. The artificial neural networks can output the driving waveform without using software programs. The shape memory alloy-type rotary actuator and the artificial neural networks are constructed with silicon wafers; they can be integrated by using micro-electromechanical system (MEMS technology. As a result, the MEMS microrobot system can locomote using step patterns. The insect-type MEMS microrobot system is 0.079 g in weight and less than 5.0 mm in size, and its locomotion speed is 2 mm/min. The locomotion speed is slow because the heat of the shape memory alloy conducts to the mechanical parts of the MEMS microrobot. In this paper, we discuss a new rotary actuator compared with the previous model and show the continuous rotation of the proposed rotary actuator.
Effect of DM actuator errors on the WFIRST/AFTA coronagraph contrast performance
Sidick, Erkin; Shi, Fang
2015-09-01
The WFIRST/AFTA 2.4 m space telescope currently under study includes a stellar coronagraph for the imaging and the spectral characterization of extrasolar planets. The coronagraph employs two sequential deformable mirrors (DMs) to compensate for phase and amplitude errors in creating dark holes. DMs are critical elements in high contrast coronagraphs, requiring precision and stability measured in picometers to enable detection of Earth-like exoplanets. Working with a low-order wavefront-sensor the DM that is conjugate to a pupil can also be used to correct low-order wavefront drift during a scientific observation. However, not all actuators in a DM have the same gain. When using such a DM in low-order wavefront sensing and control subsystem, the actuator gain calibration errors introduce highspatial frequency errors to the DM surface and thus worsen the contrast performance of the coronagraph. We have investigated the effects of actuator gain calibration errors and the actuator command digitization errors on the contrast performance of the coronagraph through modeling and simulations, and will present our results in this paper.
Biomimetic jellyfish-inspired underwater vehicle actuated by ionic polymer metal composite actuators
This paper presents the design, fabrication, and characterization of a biomimetic jellyfish robot that uses ionic polymer metal composites (IPMCs) as flexible actuators for propulsion. The shape and swimming style of this underwater vehicle are based on the Aequorea victoria jellyfish, which has an average swimming speed of 20 mm s−1 and which is known for its high swimming efficiency. The Aequorea victoria is chosen as a model system because both its bell morphology and kinematic properties match the mechanical properties of IPMC actuators. This medusa is characterized by its low swimming frequency, small bell deformation during the contraction phase, and high Froude efficiency. The critical components of the robot include the flexible bell that provides the overall shape and dimensions of the jellyfish, a central hub and a stage used to provide electrical connections and mechanical support to the actuators, eight distinct spars meant to keep the upper part of the bell stationary, and flexible IPMC actuators that extend radially from the central stage. The bell is fabricated from a commercially available heat-shrinkable polymer film to provide increased shape-holding ability and reduced weight. The IPMC actuators constructed for this study demonstrated peak-to-peak strains of ∼0.7% in water across a frequency range of 0.1–1.0 Hz. By tailoring the applied voltage waveform and the flexibility of the bell, the completed robotic jellyfish with four actuators swam at an average speed 0.77 mm s−1 and consumed 0.7 W. When eight actuators were used the average speed increased to 1.5 mm s−1 with a power consumption of 1.14 W. (paper)
Identification of micropositioning stage with piezoelectric actuators
Dong, Ruili; Tan, Yonghong; Xie, Yangqiu
2016-06-01
In this paper, a two-step identification method for a micropositioning stage with piezoelectric actuator is proposed. It is noted that one of the difficulties encountered in identification is that both input and output of the actuator embedded in the stage cannot be measured directly. Moreover, hysteresis existing in piezoelectric actuators is a non-smooth complex nonlinearity. In the proposed modeling method, a sandwich model with hysteresis is used to describe the performance of the micropositioning stage with piezoelectric actuator. In this modeling architecture, the input linear submodel is utilized to describe the behavior of preceded amplifier with filtering circuit, which provides electrical voltage to the piezoactuator, and the output linear submodel is employed to depict the flexural hinge with load, respectively, while a Duhem function embedded in between the input and output linear submodels is employed to describe the hysteresis characteristic of piezoelectric actuator in the stage. At the first step of the identification procedure, a special excitation input is implemented to excite the stage to decompose the hysteresis into a monotonic polynomial within a certain region. Then, the parameters of linear submodels are separated and estimated. Subsequently, at the second step, an input signal that can fully excite the system within the operation region is implemented to excite the stage. Based on the previously estimated linear submodels, both input and output of the piezoactuator are estimated. Then, in terms of the estimated input and output of the piezoactuator, the parameters of the hysteresis submodel are estimated. Finally, experimental results are presented to verify the proposed method.
Electrical actuation of electrically conducting and insulating droplets using ac and dc voltages
Electrical actuation of liquid droplets at the microscale offers promising applications in the fields of microfluidics and lab-on-chip devices. Much prior research has targeted the electrical actuation of electrically conducting liquid droplets using dc voltages (classical electrowetting). Electrical actuation of conducting droplets using ac voltages and the actuation of insulating droplets (using dc or ac voltages) has remained relatively unexplored. This paper utilizes an energy-minimization-based analytical framework to study the electrical actuation of a liquid droplet (electrically conducting or insulating) under ac actuation. It is shown that the electromechanical regimes of classical electrowetting, electrowetting under ac actuation and insulating droplet actuation can be extracted from the generic electromechanical actuation framework, depending on the electrical properties of the droplet, the underlying dielectric layer and the frequency of the actuation voltage. This paper also presents experiments which quantify the influence of the ac frequency and the electrical properties of the droplet on its velocity under electrical actuation. The velocities of droplets moving between two parallel plates under ac actuation are experimentally measured; these velocities are then related to the actuation force on the droplet which is predicted by the electromechanical model developed in this work. It is seen that the droplet velocities are strongly dependent on the frequency of the ac actuation voltage; the cut-off ac frequency, above which the droplet fails to actuate, is experimentally determined and related to the electrical conductivity of the liquid. This paper then analyzes and directly compares the various electromechanical regimes for the actuation of droplets in microfluidic applications
Creech, Angus; Maguire, A Eoghan
2014-01-01
We present here a computational fluid dynamics (CFD) simulation of Lillgrund offshore wind farm, which is located in the {\\O}resund Strait between Sweden and Denmark. The simulation combines a dynamic representation of wind turbines embedded within a Large-Eddy Simulation CFD solver, and uses hr-adaptive meshing to increase or decrease mesh resolution where required. This allows the resolution of both large scale flow structures around the wind farm, and local flow conditions at individual turbines; consequently, the response of each turbine to local conditions can be modelled, as well as the resulting evolution of the turbine wakes. This paper provides a detailed description of the turbine model which simulates interactions between the wind, turbine rotors, and turbine generators by calculating the forces on the rotor, the body forces on the air, and instantaneous power output. This model was used to investigate a selection of key wind speeds and directions, investigating cases where a row of turbines would ...
An Experimental Study on Active Flow Control Using Synthetic Jet Actuators over S809 Airfoil
This study investigates the effect of periodic excitation from individually controlled synthetic jet actuators on the dynamics of the flow within the separation and re-attachment regions of the boundary layer over the suction surface of a 2D model wing that has S809 airfoil profile. Experiments are performed in METUWIND's C3 open-loop suction type wind tunnel that has a 1 m × 1 m cross-section test section. The synthetic jet array on the wing consists of three individually controlled actuators driven by piezoelectric diaphragms located at 28% chord location near the mid-span of the wing. In the first part of the study, surface pressure, Constant Temperature Anemometry (CTA) and Particle Image Velocimetry (PIV) measurements are performed over the suction surface of the airfoil to determine the size and characteristics of the separated shear layer and the re-attachment region, i.e. the laminar separation bubble, at 2.3x105 Reynolds number at zero angle of attack and with no flow control as a baseline case. For the controlled case, CTA measurements are carried out under the same inlet conditions at various streamwise locations along the suction surface of the airfoil to investigate the effect of the synthetic jet on the boundary layer properties. During the controlled case experiments, the synthetic jet actuators are driven with a sinusoidal frequency of 1.45 kHz and 300Vp-p. Results of this study show that periodic excitation from the synthetic jet actuators eliminates the laminar separation bubble formed over the suction surface of the airfoil at 2.3x105 Reynolds number at zero angle of attack
As a widely used configuration for dielectric elastomer (DE) actuators, DE tube actuators (or cylindrical actuators) are also found to be susceptible to electromechanical instability (EMI), which may lead to a premature electrical breakdown (EB), and inhibit the potential actuation of DE actuators. This work investigates the electromechanical response of a DE tube actuator with and without boundary constraints to demonstrate an alternative to avoid EMI while achieving large actuation. Our simulation results based on the Gent strain energy model show that the EMI of a DE tube actuator can be eliminated, and larger actuation deformation can be achieved by applying boundary constraints. As a result of these constraints, consideration is also given to the possible mechanical buckling failure that may occur. Mechanisms of possible failure modes of constrained and unconstrained DE tube actuators, such as electromechanical instability, electrical breakdown and mechanical buckling, are elucidated. This paper should provide better theoretical guidance on how to improve the actuation performance of DE actuators, thus leading to the optimal design of DE-based devices. (paper)
Perkins, Gerald S. (Inventor)
1980-01-01
A linear actuator which can apply high forces is described, which includes a reciprocating rod having a threaded portion engaged by a nut that is directly coupled to the rotor of an electric motor. The nut is connected to the rotor in a manner that minimizes loading on the rotor, by the use of a coupling that transmits torque to the nut but permits it to shift axially and radially with respect to the rotor. The nut has a threaded hydrostatic bearing for engaging the threaded rod portion, with an oilcarrying groove in the nut being interrupted.
Tschaggeny, Charles W.; Jones, Warren F.; Bamberg, Eberhard
2011-09-13
A gimbal is described and which includes a fixed base member defining an axis of rotation; a second member concentrically oriented relative to the axis of rotation; a linear actuator oriented in immediate, adjoining force transmitting relation relative to the base member or to the second member, and which applies force along a linear axis which is tangential to the axis of rotation so as to cause the second member to rotate coaxially relative to the fixed base member; and an object of interest mounted to the second member such that the object of interest is selectively moved relative to the base member about the axis of rotation.
Laser Actuated Presentation System
Chowdhary, Atul; Agrawal, Vivek; Karmakar, Subhajit; Sarkar, Sandip
2009-01-01
We present here a pattern sensitive PowerPoint presentation scheme. The presentation is actuated by simple patterns drawn on the presentation screen by a laser pointer. A specific pattern corresponds to a particular command required to operate the presentation. Laser spot on the screen is captured by a RGB webcam with a red filter mounted, and its location is identified at the blue layer of each captured frame by estimating the mean position of the pixels whose intensity is above a given thre...
Laser Actuated Presentation System
Chowdhary, Atul; Karmakar, Subhajit; Sarkar, Sandip
2009-01-01
We present here a pattern sensitive PowerPoint presentation scheme. The presentation is actuated by simple patterns drawn on the presentation screen by a laser pointer. A specific pattern corresponds to a particular command required to operate the presentation. Laser spot on the screen is captured by a RGB webcam with a red filter mounted, and its location is identified at the blue layer of each captured frame by estimating the mean position of the pixels whose intensity is above a given threshold value. Measured Reliability, Accuracy and Latency of our system are 90%, 10 pixels (in the worst case) and 38 ms respectively.
Actuator technology and market outlook: where does the actuator move
Aleksanin Sergei Andreevich
2013-11-01
There are made conclusions about the "migration" of demand from hydraulic and pneumatic solutions to electromechanical actuators in the aerospace and manufacturing industries. Identify advantages of electromechanics over more traditional actuators in terms of energy efficiency and reliability. Also identify the most promising areas of the drive technological development.
Feng, Guo-Hua; Huang, Wei-Lun
2016-01-01
This paper presents an innovative tuning fork-shaped ionic polymer metal composite (IPMC) actuator. With an integrated soft strain gauge and water supply mechanism (WSM), the surface strain of the actuator can be sensed in situ, and providing a continuous water supply maintains the water content inside the IPMC for long-term operation in air. The actuator was fabricated using a micromachining technique and plated with a nickel electrode. The device performance was experimentally characterized and compared with an actuator without a WSM. A large displacement of 1.5 mm was achieved for a 6 mm-long prong with 7-V dc actuation applied for 30 s. The measured current was analyzed using an electrochemical model. The results revealed that the faradaic current plays a crucial role during operation, particularly after 10 s. The measured strain confirms both the bending and axial strain generation during the open-and-close motion of the actuator prongs. Most of the water loss during device operation was due to evaporation rather than hydrolysis. The constructed WSM effectively maintained the water content inside the IPMC for long-term continuous operation. PMID:27023549
Feng, Guo-Hua; Huang, Wei-Lun
2016-01-01
This paper presents an innovative tuning fork-shaped ionic polymer metal composite (IPMC) actuator. With an integrated soft strain gauge and water supply mechanism (WSM), the surface strain of the actuator can be sensed in situ, and providing a continuous water supply maintains the water content inside the IPMC for long-term operation in air. The actuator was fabricated using a micromachining technique and plated with a nickel electrode. The device performance was experimentally characterized and compared with an actuator without a WSM. A large displacement of 1.5 mm was achieved for a 6 mm-long prong with 7-V dc actuation applied for 30 s. The measured current was analyzed using an electrochemical model. The results revealed that the faradaic current plays a crucial role during operation, particularly after 10 s. The measured strain confirms both the bending and axial strain generation during the open-and-close motion of the actuator prongs. Most of the water loss during device operation was due to evaporation rather than hydrolysis. The constructed WSM effectively maintained the water content inside the IPMC for long-term continuous operation. PMID:27023549
A Complete Analysis for Pump Controlled Single Rod Actuators
Çalışkan,Hakan; Balkan, Tuna; Platin, Bülent E.
2016-01-01
In the current study a variable speed pump controlled hydrostatic circuit where an underlapped shuttle valve is utilized to compensate the unequal flow rate of a single rod actuator is analyzed. Parameters of the shuttle valve are included in the system analysis, rather than treating it as an ideal switching element as handled in literature. A linearized model of the system is obtained. An inverse kinematic model, which calculates the required pump drive speed for a desired actuator speed and...
Bioadhesion to model thermally responsive surfaces
Andrzejewski, Brett Paul
This dissertation focuses on the characterization of two surfaces: mixed self-assembled monolayers (SAMs) of hexa(ethylene glycol) and alkyl thiolates (mixed SAM) and poly(N-isopropylacrylamide) (PNIPAAm). The synthesis of hexa(ethylene gylcol) alkyl thiol (C11EG 6OH) is presented along with the mass spectrometry and nuclear magnetic resonance results. The gold substrates were imaged prior to SAM formation with atomic force micrscopy (AFM). Average surface roughness of the gold substrate was 0.44 nm, 0.67 nm, 1.65 nm for 15, 25 and 60 nm gold thickness, respectively. The height of the mixed SAM was measured by ellipsometry and varied from 13 to 28°A depending on surface mole fraction of C11EG6OH. The surface mole fraction of C11EG6OH for the mixed SAM was determined by X-ray photoelectron spectroscopy (XPS) with optimal thermal responsive behavior in the range of 0.4 to 0.6. The mixed SAM surface was confirmed to be thermally responsive by contact angle goniometry, 35° at 28°C and ˜55° at 40°C. In addition, the mixed SAM surfaces were confirmed to be thermally responsive for various aqueous mediums by tensiometry. Factors such as oxygen, age, and surface mole fraction and how they affect the thermal responsive of the mixed SAM are discussed. Lastly, rat fibroblasts were grown on the mixed SAM and imaged by phase contrast microscopy to show inhibition of attachment at temperatures below the molecular transition. Qualitative and quantitative measurements of the fibroblast adhesion data are provided that support the hypothesis of the mixed SAM exhibits a dominantly non-fouling molecular conformation at 25°C whereas it exhibits a dominantly fouling molecular conformation at 40°C. The adhesion of six model proteins: bovine serum albumin, collagen, pyruvate kinase, cholera toxin subunit B, ribonuclease, and lysozyme to the model thermally responsive mixed SAM were examined using AFM. All six proteins possessed adhesion to the pure component alkyl thiol, in
Creech, Angus; Früh, Wolf-Gerrit; Maguire, A. Eoghan
2015-05-01
We present here a computational fluid dynamics (CFD) simulation of Lillgrund offshore wind farm, which is located in the Øresund Strait between Sweden and Denmark. The simulation combines a dynamic representation of wind turbines embedded within a large-eddy simulation CFD solver and uses hr-adaptive meshing to increase or decrease mesh resolution where required. This allows the resolution of both large-scale flow structures around the wind farm, and the local flow conditions at individual turbines; consequently, the response of each turbine to local conditions can be modelled, as well as the resulting evolution of the turbine wakes. This paper provides a detailed description of the turbine model which simulates the interaction between the wind, the turbine rotors, and the turbine generators by calculating the forces on the rotor, the body forces on the air, and instantaneous power output. This model was used to investigate a selection of key wind speeds and directions, investigating cases where a row of turbines would be fully aligned with the wind or at specific angles to the wind. Results shown here include presentations of the spin-up of turbines, the observation of eddies moving through the turbine array, meandering turbine wakes, and an extensive wind farm wake several kilometres in length. The key measurement available for cross-validation with operational wind farm data is the power output from the individual turbines, where the effect of unsteady turbine wakes on the performance of downstream turbines was a main point of interest. The results from the simulations were compared to the performance measurements from the real wind farm to provide a firm quantitative validation of this methodology. Having achieved good agreement between the model results and actual wind farm measurements, the potential of the methodology to provide a tool for further investigations of engineering and atmospheric science problems is outlined.
Development of ICPF Actuated Underwater Microrobots
Xiuo-Fen Ye; Bao-Feng Gao; Shu-Xiang Guo; Li-Quan Wang
2006-01-01
It is our target to develop underwater microrobots for medical and industrial applications. This kind of underwater microrobots should have the characteristics of flexibility, good response and safety. Its structure should be simple and it can be driven by low voltage and produces no pollution or noise. The low actuating voltage and quick bending responses of Ionic Conducting Polymer Film (ICPF) are considered very useful and attractive for constructing various types of actuators and sensors. In this paper, we will first study the characteristics of the ICPF actuator used in underwater microrobot to realize swimming and walking. Then, we propose a new prototype model of underwater swimming microrobot utilizing only one piece of ICPF as the servo actuator. Through theoretic analysis, the motion mechanism of the microrobot is illustrated. It can swim forward and vertically. The relationships between moving speed and signal voltage amplitude and signal frequency is obtained after experimental study. Lastly, we present a novel underwater crab-like walking microrobot named crabliker-1. It has eight legs, and each leg is made up of two pieces of ICPF. Three sample processes of the octopod gait are proposed with a new analyzing method. The experimental results indicate that the crab-like underwater microrobot can perform transverse and rotation movement when the legs of the crab collaborate.
Gopinath, Thamilselvan; Raja, Samikannu; Ikeda, Tadashige
2011-03-01
The use of surface bonded (MFC) and embedded (SAFC) piezoelectric composite actuators is examined through a numerical study. Modelling schemes are therefore developed by applying the isoparametric finite element approach to idealize normal strain to electric field and shear strain to electric field relations. A four noded coupled finite element is developed to compute the electro-mechanical responses of the active plate. A linear quadratic regulator is employed to perform the active vibration control studies. The system matrices of the smart plate structure are obtained and used in the state-space control model. Two elastic modes are considered, namely bending and torsion of the active plate. The emphasis is given to evaluate the performance of two different kinds of flexible piezoelectric actuators in vibration control application.
Development and Analysis of Flexible Thin Actuator with a Built-in Fluid Pressure Source
Senzaki Shinji; Akagi Tetsuya; Dohta Shujiro; Fujiwara Yuto
2016-01-01
A flexible thin actuator using gas-liquid phase-change of a low boiling point liquid that can generate large force was proposed and tested in the previous study. The tested actuator is an envelope-type actuator that is made of laminating plastic sheets, low boiling point liquid and a flexible heater. In this paper, the analytical model of the flexible thin actuator was proposed and tested. The system parameters of the actuator were also identified. As a result, it was confirmed that the propo...
Elastic Cube Actuator with Six Degrees of Freedom Output
Pengchuan Wang
2015-09-01
Full Text Available Unlike conventional rigid actuators, soft robotic technologies possess inherent compliance, so they can stretch and twist along every axis without the need for articulated joints. This compliance is exploited here using dielectric elastomer membranes to develop a novel six degrees of freedom (6-DOF polymer actuator that unifies ordinarily separate components into a simple cubic structure. This cube actuator design incorporates elastic dielectric elastomer membranes on four faces which are coupled by a cross-shaped end effector. The inherent elasticity of each membrane greatly reduces kinematic constraint and enables a 6-DOF actuation output to be produced via the end effector. An electro-mechanical model of the cube actuator is presented that captures the non-linear hyperelastic behaviour of the active membranes. It is demonstrated that the model accurately predicts actuator displacement and blocking moment for a range of input voltages. Experimental testing of a prototype 60 mm device demonstrates 6-DOF operation. The prototype produces maximum linear and rotational displacements of ±2.6 mm (±4.3% and ±4.8° respectively and a maximum blocking moment of ±76 mNm. The capacity for full 6-DOF actuation from a compact, readily scalable and easily fabricated polymeric package enables implementation in a range of mechatronics and robotics applications.
Recent Advances in the Control of Piezoelectric Actuators
Ziqiang Chi
2014-11-01
Full Text Available The micro/nano positioning field has made great progress towards enabling the advance of micro/nano technology. Micro/nano positioning stages actuated by piezoelectric actuators are the key devices in micro/nano manipulation. The control of piezoelectric actuators has emerged as a hot topic in recent years. Piezoelectric materials have inherent hysteresis and creep nonlinearity, which can reduce the accuracy of the manipulation, even causing the instability of the whole system. Remarkable efforts have been made to compensate for the nonlinearity of piezoelectric actuation through the mathematical modelling and control approaches. This paper provides a review of recent advances on the control of piezoelectric actuators. After a brief introduction of basic components of typical piezoelectric micro/nano positioning platforms, the working principle and modelling of piezoelectric actuators are outlined in this paper. This is followed with the major control method and recent progress is presented in detail. Finally, some open issues and future work on the control of piezoelectric actuators are extensively discussed.
Performance Comparison of Sweeping/Steady Jet Actuators
Hirsch, Damian; Mercier, Justin; Noca, Flavio; Gharib, Morteza
2015-11-01
Flow control through the use of steady jet actuators has been used on various aircraft models since the late 1950's. However, the focus of recent studies has shifted towards the use of sweeping jets (fluidic oscillators) rather than steady jet actuators. In this work, experiments using various jet actuator designs were conducted at GALCIT's Lucas Wind Tunnel on a NACA 0012 vertical tail model similar to that of the Boeing 767 vertical stabilizer at Reynolds numbers ranging from 0.5 to 1.2 million. The rudder angle was fixed at 20 degrees. A total of 32 jet actuators were installed along the wingspan perpendicular to the trailing edge and the rudder shoulder of the vertical stabilizer. It is known that these types of flow control prevent separation. However, the goal of this work is to compare different jet designs and evaluate their performance. Parameters such as the number of actuators, their volumetric flow, and the wind tunnel speed were varied. The lift generation capabilities of steady and sweeping jet actuators were then compared. Another set of experiments was conducted to compare a new sweeping jet actuator design with one of the standard versions. Supported by Boeing.
A new MRI land surface model HAL
Hosaka, M.
2011-12-01
A land surface model HAL is newly developed for MRI-ESM1. It is used for the CMIP simulations. HAL consists of three submodels: SiByl (vegetation), SNOWA (snow) and SOILA (soil) in the current version. It also contains a land coupler LCUP which connects some submodels and an atmospheric model. The vegetation submodel SiByl has surface vegetation processes similar to JMA/SiB (Sato et al. 1987, Hirai et al. 2007). SiByl has 2 vegetation layers (canopy and grass) and calculates heat, moisture, and momentum fluxes between the land surface and the atmosphere. The snow submodel SNOWA can have any number of snow layers and the maximum value is set to 8 for the CMIP5 experiments. Temperature, SWE, density, grain size and the aerosol deposition contents of each layer are predicted. The snow properties including the grain size are predicted due to snow metamorphism processes (Niwano et al., 2011), and the snow albedo is diagnosed from the aerosol mixing ratio, the snow properties and the temperature (Aoki et al., 2011). The soil submodel SOILA can also have any number of soil layers, and is composed of 14 soil layers in the CMIP5 experiments. The temperature of each layer is predicted by solving heat conduction equations. The soil moisture is predicted by solving the Darcy equation, in which hydraulic conductivity depends on the soil moisture. The land coupler LCUP is designed to enable the complicated constructions of the submidels. HAL can include some competing submodels (precise and detailed ones, and simpler ones), and they can run at the same simulations. LCUP enables a 2-step model validation, in which we compare the results of the detailed submodels with the in-situ observation directly at the 1st step, and follows the comparison between them and those of the simpler ones at the 2nd step. When the performances of the detailed ones are good, we can improve the simpler ones by using the detailed ones as reference models.
Merging Digital Surface Models Implementing Bayesian Approaches
Sadeq, H.; Drummond, J.; Li, Z.
2016-06-01
In this research different DSMs from different sources have been merged. The merging is based on a probabilistic model using a Bayesian Approach. The implemented data have been sourced from very high resolution satellite imagery sensors (e.g. WorldView-1 and Pleiades). It is deemed preferable to use a Bayesian Approach when the data obtained from the sensors are limited and it is difficult to obtain many measurements or it would be very costly, thus the problem of the lack of data can be solved by introducing a priori estimations of data. To infer the prior data, it is assumed that the roofs of the buildings are specified as smooth, and for that purpose local entropy has been implemented. In addition to the a priori estimations, GNSS RTK measurements have been collected in the field which are used as check points to assess the quality of the DSMs and to validate the merging result. The model has been applied in the West-End of Glasgow containing different kinds of buildings, such as flat roofed and hipped roofed buildings. Both quantitative and qualitative methods have been employed to validate the merged DSM. The validation results have shown that the model was successfully able to improve the quality of the DSMs and improving some characteristics such as the roof surfaces, which consequently led to better representations. In addition to that, the developed model has been compared with the well established Maximum Likelihood model and showed similar quantitative statistical results and better qualitative results. Although the proposed model has been applied on DSMs that were derived from satellite imagery, it can be applied to any other sourced DSMs.
Electromagnetic actuation in MEMS switches
Oliveira Hansen, Roana Melina de; Mátéfi-Tempfli, Mária; Chemnitz, Steffen;
. Electromagnetic actuation is a very promising approach to operate such MEMS and Power MEMS devices, due to the long range, reproducible and strong forces generated by this method, among other advantages. However, the use of electromagnetic actuation in such devices requires the use of thick magnetic films, which...
Polypyrrole Actuators for Tremor Suppression
Skaarup, Steen; Mogensen, Naja; Bay, Lasse;
2003-01-01
exemplify 'soft actuator' technology that may be especially suitable for use in conjunction with human limbs. The electrochemical and mechanical properties of polypyrrole dodecyl benzene sulphonate actuator films have been studied with this application in mind. The results show that the time constants for...
Missile flight control using active flexspar actuators
Barrett, Ron; Gross, R. Steven; Brozoski, Fred
1996-04-01
A new type of subsonic missile flight control surface using piezoelectric flexspar actuators is presented. The flexspar design uses an aerodynamic shell which is pivoted at the quarter-chord about a graphite main spar. The shell is pitched up and down by a piezoelectric bender element which is rigidly attached to a base mount and allowed to rotate freely at the tip. The element curvature, shell pitch deflection and torsional stiffness are modeled using laminated plate theory. A one-third scale TOW 2B missile model was used as a demonstration platform. A static wing of the missile was replaced with an active flexspar wing. The 1 in 0964-1726/5/2/002/img1 2.7 in active flight control surface was powered by a bimorph bender with 5 mil PZT-5H sheets. Bench and wind tunnel testing showed good correlation between theory and experiment and static pitch deflections in excess of 0964-1726/5/2/002/img2. A natural frequency of 78.5 rad 0964-1726/5/2/002/img3 with a break frequency of 157 rad 0964-1726/5/2/002/img3 was measured. Wind tunnel tests revealed no flutter or divergence tendencies. Maximum changes in lift coefficient were measured at 0964-1726/5/2/002/img5 which indicates that terminal and initial missile load factors may be increased by approximately 3.1 and 12.6 g respectively, leading to a greatly reduced turn radius of only 2400 ft.
Filling transitions on rough surfaces: inadequacy of Gaussian surface models
Dufour, Renaud; Herminghaus, Stephan
2015-01-01
We present numerical studies of wetting on various topographic substrates, including random topographies. We find good agreement with recent predictions based on an analytical interface-displacement-type theory \\cite{Herminghaus2012, Herminghaus2012a}. The phase diagrams are qualitatively as predicted, but differently in this study the critical points are found to lie within the physical parameter range (i.e., at positive contact angle) in all cases studied. Notably, it is corroborated that Gaussian random surfaces behave qualitatively different from all non-Gaussian topographies investigated, exhibiting a qualitatively different phase diagram. This shows that Gaussian random surfaces must be used with great care in the context of wetting phenomena.
Considerations for Contractile Electroactive Materials and Actuators
Rasmussen, Lenore; Erickson, Carl J.; Meixler, Lewis D.; Ascione, George; Gentile, Charles A.; Tilson, Carl; Bernasek, Stephen L.; Abelev, Esta
2010-02-19
Ras Labs produces electroactive polymer (EAP) based materials and actuators that bend, swell, ripple and now contract (new development) with low electric input. This is an important attribute because of the ability of contraction to produce life-like motion. The mechanism of contraction is not well understood. Radionuclide-labeled experiments were conducted to follow the movement of electrolytes and water in these EAPs when activated. Extreme temperature experiments were performed on the contractile EAPs with very favorable results. One of the biggest challenges in developing these actuators, however, is the electrode-EAP interface because of the pronounced movement of the EAP. Plasma treatments of metallic electrodes were investigated in order to improve the attachment of the embedded electrodes to the EAP material. Surface analysis, adhesive testing, and mechanical testing were conducted to test metal surfaces and metal-polymer interfaces. The nitrogen plasma treatment of titanium produced a strong metal-polymer interface; however, oxygen plasma treatment of both stainless steel and titanium produced even stronger metal-polymer interfaces. Plasma treatment of the electrodes allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.
Considerations for Electroactive Polymeric Materials and Actuators
Ras Labs produces electroactive polymer (EAP) based materials and actuators that bend, swell, ripple and now contract (new development) with low electric input. This is an important attribute because of the ability of contraction to produce life-like motion. The mechanism of contraction is not well understood. Radionuclide-labeled experiments were conducted to follow the movement of electrolytes and water in these EAPs when activated. Extreme temperature experiments were performed on the contractile EAPs with very favorable results. One of the biggest challenges in developing these actuators, however, is the electrode-EAP interface because of the pronounced movement of the EAP. Plasma treatments of metallic electrodes were investigated in order to improve the attachment of the embedded electrodes to the EAP material. Surface analysis, adhesive testing, and mechanical testing were conducted to test metal surfaces and metal-polymer interfaces. The nitrogen plasma treatment of titanium produced a strong metal-polymer interface; however, oxygen plasma treatment of both stainless steel and titanium produced even stronger metal-polymer interfaces. Plasma treatment of the electrodes allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.
Printing low-voltage dielectric elastomer actuators
Poulin, Alexandre; Rosset, Samuel; Shea, Herbert R.
2015-12-01
We demonstrate the fabrication of fully printed thin dielectric elastomer actuators (DEAs), reducing the operation voltage below 300 V while keeping good actuation strain. DEAs are soft actuators capable of strains greater than 100% and response times below 1 ms, but they require driving voltage in the kV range, limiting the possible applications. One way to reduce the driving voltage of DEAs is to decrease the dielectric membrane thickness, which is typically in the 20-100 μm range, as reliable fabrication becomes challenging below this thickness. We report here the use of pad-printing to produce μm thick silicone membranes, on which we pad-print μm thick compliant electrodes to create DEAs. We achieve a lateral actuation strain of 7.5% at only 245 V on a 3 μm thick pad-printed membrane. This corresponds to a ratio of 125%/kV2, by far the highest reported value for DEAs. To quantify the increasing stiffening impact of the electrodes on DEA performance as the membrane thickness decreases, we compare two circular actuators, one with 3 μm- and one with 30 μm-thick membranes. Our experimental measurements show that the strain uniformity of the 3 μm-DEA is indeed affected by the mechanical impact of the electrodes. We developed a simple DEA model that includes realistic electrodes of finite stiffness, rather than assuming zero stiffness electrodes as is commonly done. The simulation results confirm that the stiffening impact of the electrodes is an important parameter that should not be neglected in the design of thin-DEAs. This work presents a practical approach towards low-voltage DEAs, a critical step for the development of real world applications.
A surface hydrology model for regional vector borne disease models
Tompkins, Adrian; Asare, Ernest; Bomblies, Arne; Amekudzi, Leonard
2016-04-01
Small, sun-lit temporary pools that form during the rainy season are important breeding sites for many key mosquito vectors responsible for the transmission of malaria and other diseases. The representation of this surface hydrology in mathematical disease models is challenging, due to their small-scale, dependence on the terrain and the difficulty of setting soil parameters. Here we introduce a model that represents the temporal evolution of the aggregate statistics of breeding sites in a single pond fractional coverage parameter. The model is based on a simple, geometrical assumption concerning the terrain, and accounts for the processes of surface runoff, pond overflow, infiltration and evaporation. Soil moisture, soil properties and large-scale terrain slope are accounted for using a calibration parameter that sets the equivalent catchment fraction. The model is calibrated and then evaluated using in situ pond measurements in Ghana and ultra-high (10m) resolution explicit simulations for a village in Niger. Despite the model's simplicity, it is shown to reproduce the variability and mean of the pond aggregate water coverage well for both locations and validation techniques. Example malaria simulations for Uganda will be shown using this new scheme with a generic calibration setting, evaluated using district malaria case data. Possible methods for implementing regional calibration will be briefly discussed.
Dielectric elastomer actuators for octopus inspired suction cups
Suction cups are often found in nature as attachment strategy in water. Nevertheless, the application of the artificial counterpart is limited by the dimension of the actuators and their usability in wet conditions. A novel design for the development of a suction cup inspired by octopus suckers is presented. The main focus of this research was on the modelling and characterization of the actuation unit, and a first prototype of the suction cup was realized as a proof of concept. The actuation of the suction cup is based on dielectric elastomer actuators. The presented device works in a wet environment, has an integrated actuation system, and is soft. The dimensions of the artificial suction cups are comparable to proximal octopus suckers, and the attachment mechanism is similar to the biological counterpart. The design approach proposed for the actuator allows the definition of the parameters for its development and for obtaining a desired pressure in water. The fabricated actuator is able to produce up to 6 kPa of pressure in water, reaching the maximum pressure in less than 300 ms. (paper)
Contribution of crosstalk to the uncertainty of electrostatic actuator calibrations.
Shams, Qamar A; Soto, Hector L; Zuckerwar, Allan J
2009-09-01
Crosstalk in electrostatic actuator calibrations is defined as the ratio of the microphone response to the actuator excitation voltage at a given frequency with the actuator polarization voltage turned off to the response, at the excitation frequency, with the polarization voltage turned on. It consequently contributes to the uncertainty of electrostatic actuator calibrations. Two sources of crosstalk are analyzed: the first attributed to the stray capacitance between the actuator electrode and the microphone backplate, and the second to the ground resistance appearing as a common element in the actuator excitation and microphone input loops. Measurements conducted on 1/4, 1/2, and 1 in. air condenser microphones reveal that the crosstalk has no frequency dependence up to the membrane resonance frequency and that the level of crosstalk lies at about -60 dB for all three microphones-conclusions that are consistent with theory. The measurements support the stray capacitance model. The contribution of crosstalk to the measurement standard uncertainty of an electrostatic actuator calibration is therewith 0.01 dB. PMID:19739723
Transfer Function Identification of an Electro-Rheological Actuator
Brookfield, D. J.; Dlodlo, Z. B.
A fluid clutch utilising an Electro-Rheological (ER) suspension provides a controlled torque coupling between input and output through the control of the applied electric field. If the input is driven at constant speed the device can be considered as an ER torque actuator and thus be used to drive robot links or other mechanisms requiring precise positioning. Such an ER torque actuator can replace a DC servo-motor in robotic applications with the benefits of low time constant and smooth output torque unaffected by cogging (i.e. variation in torque of a DC motor as the magnetic reluctance of the armature-stator path changes with rotation). Although the ER actuator has many benefits, it suffers from a non-linear and time varying relationship between input voltage and output torque. These undesirable characteristics can be mitigated by providing a local closed loop controller around the system. The design of such a controller requires a knowledge of the relationship between the applied voltage and output torque; i.e. the transfer function of the actuator. This transfer function has been determined by observing the response of an ER torque actuator in the frequency domain. It is shown that a linear transfer function model reasonable represents the actuator behaviour, that the actuator is a stable second order system and that the time constant of the clutch studied is sufficiently short to hold considerable promise for robotic applications. Furthermore, the maximum torque capability is shown to be sufficient for many medium scale industrial robots.
On reliable control system designs. Ph.D. Thesis; [actuators
Birdwell, J. D.
1978-01-01
A mathematical model for use in the design of reliable multivariable control systems is discussed with special emphasis on actuator failures and necessary actuator redundancy levels. The model consists of a linear time invariant discrete time dynamical system. Configuration changes in the system dynamics are governed by a Markov chain that includes transition probabilities from one configuration state to another. The performance index is a standard quadratic cost functional, over an infinite time interval. The actual system configuration can be deduced with a one step delay. The calculation of the optimal control law requires the solution of a set of highly coupled Riccati-like matrix difference equations. Results can be used for off-line studies relating the open loop dynamics, required performance, actuator mean time to failure, and functional or identical actuator redundancy, with and without feedback gain reconfiguration strategies.
2008-01-01
Detailed two-dimensional unsteady numerical simulation is carried out to investigate a high-power synthetic jet actuator flow field and its design characteristic. Simultaneously, mixing control mechanism of coaxial jets with actuators is also studied. Firstly, excitation frequency (rotating speed), piston displacement and its exit slot width have effect on the controlling ability and controlling efficiency of actuator. With the invariable model and concerned parameters, the actuator becomes more desirable as the rotating speed increases. Average velocity and maximal velocity at the actuator exit section increase as the piston displacement enlarges or the exit slot width decreases. But the actuator does not always exhibit good performance with the narrower exit. Secondly, the synthetic jets also have the "push" effect on the coaxial jets, which results in the fluctuation of vorticity and temperature distribution of mixing fiowfield. Finally, the employment of synthetic jet actuator can achieve mixing enhancement significantly.
Linear electrochemical gel actuators
Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.
2012-04-01
By using electroactive monomers it is possible to produce gels that respond to oxidation or reduction by swelling and deswelling in the presence of solvent. By the inclusion of an appropriate biasing element such as a spring, it is possible to produce linear, reversible actuation. The process can be driven electrochemically in a standard cell, with driving voltages under +/- 1 V. For many systems, the intrinsic conductivity of the gel, leading to poor or no performance. This can be overcome by blending conductive carbon nanotubes at 1% concentration, which give reasonable conductivity without affecting mechanical performance. Extensions of up to 40% are possible, against an external pressure of 30 kPa. The process is slow, taking up to 160 minutes per cycle due to slow ionic diffusion. The electrochemical cell can be cycled many times without degradation.
Larsen, Jeppe Veirum; Overholt, Daniel; Moeslund, Thomas B.
2014-01-01
functioning hands. In this study we try to enable people with Hemiplegia to play a real electrical guitar, by modifying it in a way that allows people with Hemiplegia able to actually use the instrument. We developed a guitar platform utilizing sensors to capture the rhythmic motion of alternate fully......, thereby making it easier to adapt to individual users. To validate and test the instrument platform we collaborated with the Helena Elsass Center in Copenhagen, Denmark during their 2013 Summer Camp, to see if we actually succeeded in creating an electrical guitar that children with Hemiplegia could play....... The initial user studies showed that children with Hemiplegia were able to play the actuated guitar by producing rhythmical movement across the strings, enabling them to enter a world of music they so often see as closed....
Investigations on Actuator Dynamics through Theoretical and Finite Element Approach
Somashekhar S. Hiremath
2010-01-01
Full Text Available This paper gives a new approach for modeling the fluid-structure interaction of servovalve component-actuator. The analyzed valve is a precision flow control valve-jet pipe electrohydraulic servovalve. The positioning of an actuator depends upon the flow rate from control ports, in turn depends on the spool position. Theoretical investigation is made for No-load condition and Load condition for an actuator. These are used in finite element modeling of an actuator. The fluid-structure-interaction (FSI is established between the piston and the fluid cavities at the piston end. The fluid cavities were modeled with special purpose hydrostatic fluid elements while the piston is modeled with brick elements. The finite element method is used to simulate the variation of cavity pressure, cavity volume, mass flow rate, and the actuator velocity. The finite element analysis is extended to study the system's linearized response to harmonic excitation using direct solution steady-state dynamics. It was observed from the analysis that the natural frequency of the actuator depends upon the position of the piston in the cylinder. This is a close match with theoretical and simulation results. The effect of bulk modulus is also presented in the paper.
On the Nature and Behavior of Filaments in the Dielectric Barrier Discharge of Plasma Actuators
Bürkle, Sebastian
2013-01-01
Plasma actuators based on dielectric barrier discharge (DBD) promise a bright future in aerodynamical applications. By creating a body force in the surrounding gas through plasma – gas interaction, plasma actuators operated in quiescent air induce a small flow above their surface with a velocity of typically 5-8 m/s, the so called ionic wind. The ionic wind can influence the boundary-layer of an externally applied flow surrounding the actuator. Unfortunately, the origin of the body force that...
Effect of the duty cycle on the spark-plug plasma synthetic jet actuator
Seyhan Mehmet; Akansu Yahya Erkan; Karakaya Fuat; Yesildag Cihan; Akbıyık Hürrem
2016-01-01
A promising novel actuator called Spark-Plug Plasma Synthetic Jet (SPSJ) has been developed in Atmospheric Plasma Research Laboratory at Niğde University. It generates electrothermally high synthetic jet velocity by using high voltage. SPSJ actuator can be utilized to be an active flow control device having some advantages such as no moving parts, low energy consumption and easy to integrate the system. This actuator consists of two main components: semi-surface spark plug (NGK BUHW) as an an...
Modular Architecture of a Non-Contact Pinch Actuation Micropump
Ruzairi Abdul Rahim
2012-09-01
Full Text Available This paper demonstrates a modular architecture of a non-contact actuation micropump setup. Rapid hot embossing prototyping was employed in micropump fabrication by using printed circuit board (PCB as a mold material in polymer casting. Actuator-membrane gap separation was studied, with experimental investigation of three separation distances: 2.0 mm, 2.5 mm and 3.5 mm. To enhance the micropump performance, interaction surface area between plunger and membrane was modeled via finite element analysis (FEA. The micropump was evaluated against two frequency ranges, which comprised a low driving frequency range (0–5 Hz, with 0.5 Hz step increments and a nominal frequency range (0–80 Hz, with 10 Hz per step increments. The low range frequency features a linear relationship of flow rate with the operating frequency function, while two magnitude peaks were captured in the flow rate and back pressure characteristic in the nominal frequency range. Repeatability and reliability tests conducted suggest the pump performed at a maximum flow rate of 5.78 mL/min at 65 Hz and a backpressure of 1.35 kPa at 60 Hz.
Soft pneumatic actuator skin with piezoelectric sensors for vibrotactile feedback
Harshal Arun Sonar
2016-01-01
Full Text Available The latest wearable technologies demand more intuitive and sophisticated interfaces for communication, sensing, and feedback closer to the body. Evidently, such interfaces require flexibility and conformity without losing their functionality even on rigid surfaces. Although there has been various research efforts in creating tactile feedback to improve various haptic interfaces and master-slave manipulators, we are yet to see a comprehensive device that can both supply vibratory actuation and tactile sensing. This paper describes a soft pneumatic actuator (SPA based, SPA-skin prototype that allows bidirectional tactile information transfer to facilitate simpler and responsive wearable interface. We describe the design and fabrication of a 1.4 mm-thick vibratory SPA - skin that is integrated with piezoelectric sensors. We examine in detail the mechanical performance compared to the SPA model and the sensitivity of the sensors for the application in vibrotactile feedback. Experimental findings show that this ultra-thin SPA and the unique integration process of the discrete lead zirconate titanate (PZT based piezoelectric sensors achieve high resolution of soft contact sensing as well as accurate control on vibrotactile feedback by closing the control loop.
Bluff body flow control with atmospheric plasma actuators
Huang, X.; Zhang, X.; Gabriel, S
2008-01-01
Plasma actuators operating in atmospheric air were employed to modify aerodynamic flow over a bluff body. The model consisted of a cylinder and a strut that was installed on the trailing half side of the cylinder. The objective was to reduce the broadband noise that is mainly generated by the impingment of the cylinder wake on the strut. The plasma actuators were configured to produce dielectric barrier discharges, through which the flow separation from the cylinder was enhanced. As a result ...
Design of actuator system for industrial robots
Santaulària Arbonés, Oriol
2010-01-01
Heavy-duty robots are used in a wide range of industrial applications. During the last years the handling capacity and a reduced cycle time requirements have been increased without compromising the robot quality. The purpose of this master thesis is to design and simulate an actuator system for motion control suitable for a three joint robot. Before analyzing the 3-DOF model, a theoretical kinematic and dynamic analysis is performed. This theoretical foundation gives the basis to later dec...
Crone control of a nonlinear hydraulic actuator
Pommier-Budinger, Valérie; Sabatier, Jocelyn; Lanusse, Patrick; Oustaloup, Alain
2002-01-01
The CRONE control (fractional robust control) of a hydraulic actuator whose dynamic model is nonlinear is presented. An input-output linearization under diffeomorphism and feedback is first achieved for the nominal plant. The relevance of this linearization when the parameters of the plant vary is then analyzed using the Volterra input-output representation in the frequency domain. CRONE control based on complex fractional differentiation is finally applied to control the velocity of the inpu...
Pneumatic actuator with hydraulic control
Everett, Hobart R., Jr.
1992-11-01
The present invention provides a pneumatically powered actuator having hydraulic control for both locking and controlling the velocity of an output rod without any sponginess. The invention includes a double-acting pneumatic actuator having a bore, a piston slidably engaged within the bore, and a control rod connected to the piston. The double-acting pneumatic actuator is mounted to a frame. A first double-acting hydraulic actuator having a bore, a piston slidably engaged within the bore, and a follower rod mounted to the piston is mounted to the frame such that the follower rod is fixedly connected to the control rod. The maximum translation of the piston within the bore of the first double-acting hydraulic actuator provides a volumetric displacement V1. The present invention also includes a second double-acting hydraulic actuator having a bore, a piston slidably engaged within the bore, and an output rod mounted to the piston. The maximum translation of the piston within the bore of the second double-acting hydraulic actuator provides a volumetric displacement V2, where V2=V1. A pair of fluid ports in each of the first and second double-acting hydraulic cylinders are operably connected by fluid conduits, one of which includes a valve circuit which may be used to control the velocity of the output rod or to lock the output rod in a static position by regulating the flow of hydraulic fluid between the double-acting cylinders.
Gear-Driven Turnbuckle Actuator
Rivera, Ricky N.
2010-01-01
This actuator design allows the extension and contraction of turnbuckle assemblies. It can be operated manually or remotely, and is extremely compact. It is ideal for turnbuckles that are hard to reach by conventional tools. The tool assembly design solves the problem of making accurate adjustments to the variable geometry guide vanes without having to remove and reinstall the actuator system back on the engine. The actuator does this easily by adjusting the length of the turnbuckles while they are still attached to the engine.
Optimal compliant-surface jumping: a multi-segment model of springboard standing jumps.
Cheng, Kuangyou B; Hubbard, Mont
2005-09-01
A multi-segment model is used to investigate optimal compliant-surface jumping strategies and is applied to springboard standing jumps. The human model has four segments representing the feet, shanks, thighs, and trunk-head-arms. A rigid bar with a rotational spring on one end and a point mass on the other end (the tip) models the springboard. Board tip mass, length, and stiffness are functions of the fulcrum setting. Body segments and board tip are connected by frictionless hinge joints and are driven by joint torque actuators at the ankle, knee, and hip. One constant (maximum isometric torque) and three variable functions (of instantaneous joint angle, angular velocity, and activation level) determine each joint torque. Movement from a nearly straight motionless initial posture to jump takeoff is simulated. The objective is to find joint torque activation patterns during board contact so that jump height can be maximized. Minimum and maximum joint angles, rates of change of normalized activation levels, and contact duration are constrained. Optimal springboard jumping simulations can reasonably predict jumper vertical velocity and jump height. Qualitatively similar joint torque activation patterns are found over different fulcrum settings. Different from rigid-surface jumping where maximal activation is maintained until takeoff, joint activation decreases near takeoff in compliant-surface jumping. The fulcrum-height relations in experimental data were predicted by the models. However, lack of practice at non-preferred fulcrum settings might have caused less jump height than the models' prediction. Larger fulcrum numbers are beneficial for taller/heavier jumpers because they need more time to extend joints. PMID:16023469
High-frequency jet nozzle actuators for noise reduction
Davis, Christopher L.; Calkins, Frederick T.; Butler, George W.
2003-08-01
Rules governing airport noise levels are becoming more restrictive and will soon affect the operation of commercial air traffic. Sound produced by jet engine exhaust, particularly during takeoff, is a major contributor to the community noise problem. The noise spectrum is broadband in character and is produced by turbulent mixing of primary, secondary, and ambient streams of the jet engine exhaust. As a potential approach to controlling the noise levels, piezoelectric bimorph actuators have been tailored to enhance the mixing of a single jet with its quiescent environment. The actuators are located at the edge of the nozzle and protrude into the exhaust stream. Several actuator configurations were considered to target two excitation frequencies, 250 Hz and 900 Hz, closely coupled to the naturally unstable frequencies of the mixing process. The piezoelectric actuators were constructed of 10 mil thick d31 poled wafer PZT-5A material bonded to either 10 or 20 mil thick spring steel substrates. Linear analytical beam models and NASTRAN finite element models were used to predict and assess the dynamic performance of the actuators. Experimental mechanical and electrical performance measurements were used to validate the models. A 3 inch diameter nozzle was fitted with actuators and tested in the Boeing Quiet Air Facility with the jet velocity varied from 50 to 1000 ft/s. Performance was evaluated using near-field and far-field acoustic data, flow visualization, and actuator health data. The overall sound pressure level produced from the 3 inch diameter jet illustrates the effect of both static and active actuators.
Low Spring Index NiTi Coil Actuators for Use in Active Compression Garments
Holschuh, Bradley T.; Obropta, Edward W.; Newman, Dava
2014-01-01
This paper describes the modeling, development, and testing of low spring index nickel titanium (NiTi) coil actuators designed for use in wearable compression garments, and presents a prototype tourniquet system using these actuators. NiTi coil actuators produce both large forces (>1 N) and large recoverable displacements (>100% length) that are well suited for compression garment design. Thermomechanical coil models are presented that describe temperature and force as a function of nondimens...
Synthetic jet actuation for load control
The reduction of wind turbine blade loads is an important issue in the reduction of the costs of energy production. Reduction of the loads of a non-cyclic nature requires so-called smart rotor control, which involves the application of distributed actuators and sensors to provide fast and local changes in aerodynamic performance. This paper investigates the use of synthetic jets for smart rotor control. Synthetic jets are formed by ingesting low-momentum fluid from the boundary layer along the blade into a cavity and subsequently ejecting this fluid with a higher momentum. We focus on the observed flow phenomena and the ability to use these to obtain the desired changes of the aerodynamic properties of a blade section. To this end, numerical simulations and wind tunnel experiments of synthetic jet actuation on a non-rotating NACA0018 airfoil have been performed. The synthetic jets are long spanwise slits, located close to the trailing edge and directed perpendicularly to the surface of the airfoil. Due to limitations of the present experimental setup in terms of performance of the synthetic jets, the main focus is on the numerical flow simulations. The present results show that high-frequency synthetic jet actuation close to the trailing edge can induce changes in the effective angle of attack up to approximately 2.9°
Magnetically Actuated Cilia for Microfluidic Manipulation
Hanasoge, Srinivas; Owen, Drew; Ballard, Matt; Hesketh, Peter J.; Alexeev, Alexander; Woodruff School of Mechanical Engineering Collaboration; Petit InstituteBioengineering; Biosciences Collaboration
2015-11-01
We demonstrate magnetic micro-cilia based microfluidic mixing and capture techniques. For this, we use a simple and easy to fabricate high aspect ratio cilia, which are actuated magnetically. These micro-features are fabricated by evaporating NiFe alloy at room temperature, on to patterned photoresist. The evaporated alloy curls upwards when the seed layer is removed to release the cilia, thus making a free standing `C' shaped magnetic microstructure. This is actuated using an external electromagnet or a rotating magnet. The artificial cilia can be actuated upto 20Hz. We demonstrate the active mixing these cilia can produce in the microchannel. Also, we demonstrate the capture of target species in a sample using these fast oscillating cilia. The surface of the cilia is functionalized by streptavidin which binds to biotin labelled fluorescent microspheres and mimic the capture of bacteria. We show very high capture efficiencies by using these methods. These simple to fabricate micro cilia can easily be incorporated into many microfluidic systems which require high mixing and capture efficiencies.
Climbing robot actuated by meso-hydraulic artificial muscles
Bryant, Matthew; Fitzgerald, Jason; Miller, Samuel; Saltzman, Jonah; Kim, Sangkyu; Lin, Yong; Garcia, Ephrahim
2014-03-01
This paper presents the design, construction, experimental characterization, and system testing of a legged, wall-climbing robot actuated by meso-scale hydraulic artificial muscles. While small wall-climbing robots have seen increased research attention in recent years, most authors have primarily focused on designs for the gripping and adhesion of the robot to the wall, while using only standard DC servo-motors for actuation. This project seeks to explore and demonstrate a different actuation mechanism that utilizes hydraulic artificial muscles. A four-limb climbing robot platform that includes a full closed-loop hydraulic power and control system, custom hydraulic artificial muscles for actuation, an on-board microcontroller and RF receiver for control, and compliant claws with integrated sensing for gripping a variety of wall surfaces has been constructed and is currently being tested to investigate this actuation method. On-board power consumption data-logging during climbing operation, analysis of the robot kinematics and climbing behavior, and artificial muscle force-displacement characterization are presented to investigate and this actuation method.
MOSFET Switching Circuit Protects Shape Memory Alloy Actuators
Gummin, Mark A.
2011-01-01
A small-footprint, full surface-mount-component printed circuit board employs MOSFET (metal-oxide-semiconductor field-effect transistor) power switches to switch high currents from any input power supply from 3 to 30 V. High-force shape memory alloy (SMA) actuators generally require high current (up to 9 A at 28 V) to actuate. SMA wires (the driving element of the actuators) can be quickly overheated if power is not removed at the end of stroke, which can damage the wires. The new analog driver prevents overheating of the SMA wires in an actuator by momentarily removing power when the end limit switch is closed, thereby allowing complex control schemes to be adopted without concern for overheating. Either an integral pushbutton or microprocessor-controlled gate or control line inputs switch current to the actuator until the end switch line goes from logic high to logic low state. Power is then momentarily removed (switched off by the MOSFET). The analog driver is suited to use with nearly any SMA actuator.
Energy-Efficient Variable Stiffness Actuators
Visser, Ludo C.; Carloni, Raffaella; Stramigioli, Stefano
2011-01-01
Variable stiffness actuators are a particular class of actuators that is characterized by the property that the apparent output stiffness can be changed independent of the output position. To achieve this, variable stiffness actuators consist of a number of elastic elements and a number of actuated
徐莉; 刘飞
2011-01-01
Aiming at a class of discrete-time nonlinear systems subject to actuator saturation and output constraint, a novel fuzzy predictive control method is proposed in this paper.Firstly,the approximation of a practical nonlinear system is realized by utilizing the T-S fuzzy model.Then,the above system is further converted into convex combinations of a series of linear subsystems by Parallel Distributed Compensation(PDC) scheme.Secondly,a state feedback predictive controller is obtained by optimizing an infinite time "min-max" performance index at each sampling instantA sufficient condition for the Lyapunov asymptotical stability is obtained and it is further transformed into positive Semi-definite Programming(SDP) which can be easily solved by means of Linear Matrix Inequality (LMI).Finally, the availability and feasibility of the proposed method are both verified by specific numerical examples,respectively.%针对一类具有执行器饱和与输出约束的离散非线性时滞系统,提出新的模糊预测控制方法.首先,采用T-S模糊模型来逼近实际非线性系统,运用平行分步补偿(PDC)原理将该系统转化为一系列线性系统的凸组合.其次,通过每个采样时刻优化无穷时域的“min-max”性能指标来求解状态反馈预测控制器,得到系统满足Lyapunov渐近稳定的充分条件,并进一步将该条件转化为基于线性矩阵不等式(LMI)技术的半正定规划(SDP)问题.最后,通过数值仿真验证该方法的有效性.
Closed surface modeling with helical line measurement data
LI Ruqiong; LI Guanghu; WANG Yuhan
2007-01-01
Models for surface modeling of free-form surface and massive data points are becoming an important feature in commercial computer aided design/computer-aided manu- facturing software. However, there are many problems to be solved in this area, especially for closed free-form surface modeling. This article presents an effective method for cloud data closed surface modeling from asynchronous profile modeling measurement. It includes three steps: first, the cloud data are preprocessed for smoothing; second, a helical line is segmented to form triangle meshes; and third, Bezier surface patches are created over a triangle mesh and trimmed to shape on an entire surface. In the end, an illustrative example of shoe last surface modeling is given to show the availability of this method.