Showing papers on "Actuator published in 2008"
TL;DR: In this article, a review of the developments in dielectric elastomer actuator technology for several applications is presented, highlighting some of its advantages over existing actuator technologies, identifying some of the challenges associated with its development, and examining the main focus of research within this field.
Abstract: This paper reviews the developments in dielectric elastomer actuator technology for several applications. Dielectric elastomers are a variety of electroactive polymer that deform due to the electrostatic interaction between two electrodes with opposite electric charge. Dielectric elastomers have been subject of much interest and research over the past decade. In earlier years, much of the focus was on actuator configurations, and in more recent years the focus has turned to investigating material properties that may enhance actuator performance. This review outlines the operating principle and actuation mechanisms behind this actuator technology, highlights some of its advantages over existing actuator technologies, identifies some of the challenges associated with its development, and examines the main focus of research within this field, including some of the potential applications of such an actuator technology.
677 citations
TL;DR: In this article, the authors present the state of the art of the magnetostrictive materials and their applications such as: Reaction Mass Actuator, A standard Terfenol-D Actuators, Linear Motor Based on Terfenolin-D (Worm Motor), Terfenoline-D in Sonar Transducers, Terfenolate-D Wireless Rotational Motor, Terfetol-d Electro-Hydraulic ActuATOR, Wireless Linear Micro-Motor, Magnetostriction Film Applications, Magnetstrictive Contactless Torque Sensors and many
412 citations
19 May 2008
TL;DR: VSA-II overcomes the problem of implementability with higher capacities and robustness in design for longer life with a comparison of stiffness characteristics between the two actuator, highlighting the advantages of the new design.
Abstract: This paper presents design and performance of a novel joint based actuator for a robot run by variable stiffness actuation, meant for systems physically interacting with humans. This new actuator prototype (VSA-II) is developed as an improvement over our previously developed one reported in [9], where an optimal mechanical-control co-design principle established in [7] is followed as well. While the first version was built in a way to demonstrate effectiveness of variable impedance actuation (VIA), it had limitations in torque capacities, life cycle and implementability in a real robot. VSA-II overcomes the problem of implementability with higher capacities and robustness in design for longer life. The paper discusses design and stiffness behaviour of VSA-II in theory and experiments. A comparison of stiffness characteristics between the two actuator is discussed, highlighting the advantages of the new design. A simple, but effective PD scheme is employed to independently control joint-stiffness and joint-position of a 1-link arm. Finally, results from performed impact tests of 1- link arm are reported, showing the effectiveness of stiffness variation in controlling value of a safety metric.
353 citations
01 Dec 2008
TL;DR: Two novel distributed implementations of event-triggered and self- Triggered policies over sensor/actuator networks are introduced and their performance in terms of energy expenditure is discussed.
Abstract: Event-triggered and self-triggered control have been recently proposed as an alternative to the more traditional periodic execution of control tasks. The possibility of reducing the number of executions while guaranteeing desired levels of performance makes event-triggered and self-triggered control very appealing in the context of sensor/actuator networks. In this setting, reducing the number of times that a feedback control law is executed implies a reduction in transmissions and thus a reduction in energy expenditures. In this paper we introduce two novel distributed implementations of event-triggered and self-triggered policies over sensor/actuator networks and discuss their performance in terms of energy expenditure.
284 citations
TL;DR: In this article, a self-sensing method based on the dielectric elastomer (DE) actuator/sensor was successfully developed and evaluated in order to extract accurate displacement information during the actuation process without using any additional sensing device.
Abstract: A novel self-sensing method based on the dielectric elastomer (DE) actuator/sensor, was successfully developed and evaluated in order to extract accurate displacement information during the actuation process without using any additional sensing device. The proposed self-sensing method is based on a capacitance characteristic of a DE actuator. The DE actuator with a serial external resistor can serve as an electrical high-pass filter. The voltage gained using the high-pass filter, which is virtually built by the DE, varies due to the change of overall capacitance when the DE actuator is expanded electro-mechanically. To realize actuating and sensing simultaneously with a DE actuator, we used a modulation technique to mix signals, which have a low frequency signal for actuating and a high frequency with small amplitude for sensing. Several experiments were performed to verify the usability of the proposed self-sensing method. The results showed a fine resolution and an excellent correlation with the displacements measured by a laser displacement sensor.
242 citations
TL;DR: In this article, a physics-based model is developed for IPMC actuators, which is amenable to model reduction and control design, and an Hinfin controller is designed based on the reduced model and applied to tracking control.
Abstract: Ionic polymer-metal composite (IPMC) actuators have promising applications in biomimetic robotics, biomedical devices, and micro/nanomanipulation. In this paper, a physics- based model is developed for IPMC actuators, which is amenable to model reduction and control design. The model is represented as an infinite-dimensional transfer function relating the bending displacement to the applied voltage. It is obtained by exactly solving the governing partial differential equation in the Laplace domain for the actuation dynamics, where the effect of the distributed surface resistance is incorporated. The model is expressed in terms of fundamental material parameters and actuator dimensions, and is thus, geometrically scalable. To illustrate the utility of the model in controller design, an Hinfin controller is designed based on the reduced model and applied to tracking control. Experimental results are presented to validate the proposed model and its effectiveness in real-time control design.
228 citations
TL;DR: This work considers the problem of control actuator fault detection and isolation and fault-tolerant control for a multi-input multi-output nonlinear system subject to constraints on the manipulated inputs and proposes a fault Detection and isolation filter and controller reconfiguration design.
222 citations
TL;DR: In this paper, the bucky-gel actuator was fabricated by hot-pressing the prepared electrode and electrolyte layers and analyzed its experimental results by the tri-layer polymer actuator model which was developed by Alici et al. for conducting polymer actuators.
207 citations
TL;DR: In this article, the authors reviewed the world-wide study on micro-motion systems both from an academic and an industrial perspective and concluded that the PZT actuation element integrated with the compliant mechanism is the most promising technology which can achieve high accuracy (sub-nanometer) of all four kinds of motion ranges.
Abstract: In this paper we review the world-wide study on micro-motion systems both from an academic and an industrial perspective. The objective of the review is to answer the following questions: (1) What are the limitations of technologies to develop a micro-motion device in terms of function, motion range, accuracy, and speed it can achieve? (2) What is any economic implication of these technologies? (3) What are future research directions? The micro-motion systems considered in this paper are classified into four kinds in terms of their motion ranges: (a) 1000 μm. This review concludes that the PZT actuation element integrated with the compliant mechanism is the most promising technology which can achieve high accuracy (sub-nanometer) of all four kinds of motion ranges. This promise is further based on the amplification technology using the compliant mechanism concept. The amplification mechanism is used to com- pensate the problem with a limited stroke of the PZT actuation element. The compliant amplification mecha- nism allows one to achieve a high resolution and high stiffness motion which does not compromise the loss of accuracy due to motion amplification. The PZT actuation element and the compliant mechanism are both econom- ically viable. Future research direction should generally focus on the interface between the PZT actuation element and compliant mechanism and the reliability of the compliant mechanism under cyclic deformation of com- pliant materials.
203 citations
TL;DR: In this paper, the optimal placement of collocated piezoelectric actuator?sensor pairs on flexible beams using a model-based linear quadratic regulator (LQR) controller is considered.
Abstract: This paper considers the optimal placement of collocated piezoelectric actuator?sensor pairs on flexible beams using a model-based linear quadratic regulator (LQR) controller. A finite element method based on Euler?Bernoulli beam theory is used. The contributions of piezoelectric sensor and actuator patches to the mass and stiffness of the beam are considered. The LQR performance is taken as the objective for finding the optimal location of sensor?actuator pairs. The problem is formulated as a multi-input multi-output (MIMO) model control. The discrete optimal sensor and actuator location problem is formulated in the framework of a zero?one optimization problem which is solved using genetic algorithms (GAs). Classical control strategies like direct proportional feedback, constant gain negative velocity feedback and the LQR optimal control scheme are applied to study the control effectiveness. The study of the optimal location of actuators and sensors is carried out for different boundary conditions of beams like cantilever, simply supported and clamped boundary conditions.
186 citations
TL;DR: In this paper, a vibrating surface driven by an electromagnetic turbulator was mounted in a flat plate to excite the Tollmien-Schlichting (TS) waves and these were amplified by an adverse pressure gradient induced by an insert on the upper wall of the test section.
Abstract: In the present work artificially excited Tollmien–Schlichting (TS) waves were cancelled using plasma actuators operated in pulsed mode. In order to achieve this a vibrating surface driven by an electromagnetic turbulator was flush mounted in a flat plate to excite the TS waves. These were amplified by an adverse pressure gradient induced by an insert on the upper wall of the test section. A control plasma actuator positioned downstream of the excitation actuator attenuates the waves by imparting an unsteady force into the boundary layer to counteract the oscillation. As a result the amplitude of the velocity fluctuations at the excitation frequency is reduced significantly depending on the distance from the wall. A parameter study was performed to identify the influence of several operation parameters of the control actuator.
TL;DR: In this paper, a simple approach is introduced for rapid online estimation of system delay and actuator command gain, thus capturing the variability of system response through a simulation, and an extrapolation procedure for delay compensation, based on the same kinematics equations used in numerical integration procedures is examined.
Abstract: Compensation of delay and dynamic response of servo-hydraulic actuators is critical for stability and accuracy of hybrid experimental and numerical simulations of seismic response of structures. In this study, current procedures for compensation of actuator delay are examined and improved procedures are proposed to minimize experimental errors. The new procedures require little or no a priori information about the behavior of the test specimen or the input excitation. First, a simple approach is introduced for rapid online estimation of system delay and actuator command gain, thus capturing the variability of system response through a simulation. Second, an extrapolation procedure for delay compensation, based on the same kinematics equations used in numerical integration procedures is examined. Simulations using the proposed procedures indicate a reduction in high-frequency noise in force measurements that can minimize the excitation of high-frequency modes. To further verify the effectiveness of the compensation procedures, the artificial energy added to a hybrid simulation as a result of actuator tracking errors is measured and used for demonstrating the improved accuracy in the simulations.
Patent•
20 Jun 2008
TL;DR: In this paper, a pipe expander assembly is described, which consists of a first actuator and a second actuator, spaced apart from the first and operatively engaged therewith.
Abstract: An assembly for actuating a pipe expander, the assembly comprising a first actuator, arranged to engage a pipe expander head and actuate the same a second actuator, spaced apart from the first actuator and operatively engaged therewith such that operation of the second actuator effects operation of the first actuator to actuate the pipe expander head.
TL;DR: In this article, a novel electrothermal actuator design that can generate large vertical displacements with almost no lateral shift was reported, and the lateral shift free piston motion was achieved by using a unique three-bimorph actuation mechanism.
Abstract: This paper reports a novel electrothermal actuator design that can generate large vertical displacements with almost no lateral shift. The lateral-shift-free (LSF) piston motion is achieved by using a unique three-bimorph actuation mechanism. Both micromirrors and microlens holders based on this new actuator design have been fabricated using a combined surface- and bulk-micromachining process. A 0.62 mm vertical displacement is measured at only 5.3 V for a fabricated 0.8 mm by 0.8 mm micromirror, and both the lateral shift (10 μm) and tilting angle (0.7°) are very small in that full vertical displacement range. The measured resonant frequency of the vertical motion mode is about 0.5 KHz. The thermal response time is about 25 ms.
TL;DR: The control synthesis problem for a class of linear time-delay systems with actuator saturation is investigated and the corresponding existence conditions of the stabilizing state-feedback controller are derived in terms of LMIs.
TL;DR: In this paper, an electrical characterization technique for obtaining information on the transient strain in the actuator and analyzing the behavior of the actuators in safe and failure operation regimes, in particular in the pull-in instability mode, is presented.
Abstract: Dielectric elastomer actuators (DEAs) are promising structural units for artificial muscles and robotic elements. Understanding the safe and failure mode regimes of such DEAs is essential for controlling the actuator. We develop an electrical characterization technique for obtaining information on the transient strain in the actuator and analyze the behavior of the actuator in safe and failure operation regimes, in particular in the pull-in instability mode. Additionally, the technique allows the strain-dependent measurement of the electrode resistance. The current measurement based technique can be also applied for actuator control with feedback loops.
TL;DR: A cascaded sliding-mode (SM) control scheme for a new pneumatic linear axis which could be seen as alternative to an electric direct linear drive and shows an excellent control performance that outperforms alternative control approaches in a comparison.
Abstract: This paper presents a cascaded sliding-mode (SM) control scheme for a new pneumatic linear axis which could be seen as alternative to an electric direct linear drive. Its guided carriage is driven by a nonlinear mechanism consisting of a rocker with an antagonistic pair of pneumatic muscle actuators arranged at both sides. This innovative drive concept allows for both an increased workspace of approximately 1 m as well as higher carriage velocities of approximately 1.3 m/s as compared to a direct actuation. Modeling of the muscle-driven positioning system leads to a system of four nonlinear differential equations including polynomial approximations of the volume characteristic as well as the force characteristic of the pneumatic muscles. The differential flatness of the system is exploited in combination with SM techniques to stabilize the error dynamics in view of unmodeled dynamics. The internal pressure of each pneumatic muscle is controlled by a fast underlying control loop. Hence, the control design for the outer control loop can be simplified by considering these controlled muscle pressures as ideal control inputs. The control design of the outer control loop involves a decoupling of rocker angle as well as mean internal pressure of both pneumatic muscles as flat outputs. Additionally, model uncertainties in the equation of motion like nonlinear friction are directly counteracted by an observer-based disturbance compensation which reduces the chattering problem. Experimental results show an excellent control performance that outperforms alternative control approaches in a comparison.
TL;DR: A new modeling approach and control law for pneumatic servo actuators are presented and the use of novel bipolynomial functions to model the valve flow rates is shown to produce a more accurate solution than prior approaches.
Abstract: Pneumatic actuators are low-cost, safe, clean, and exhibit a high power to weight ratio. In this paper a new modeling approach and control law for pneumatic servo actuators are presented. The nonlinear system model is developed using a combination of mechanistic and empirical methods. The use of novel bipolynomial functions to model the valve flow rates is shown to produce a more accurate solution than prior approaches. A novel multiple-input single-output nonlinear position control law is designed using the backstepping methodology. The stability analysis includes the effects of friction modeling error and valve modeling error. Experiments are conducted with 9.5-mm bore and 6.4-mm bore pneumatic cylinders, and four low-cost two-way proportional valves. In experiments with the 9.5-mm bore cylinder and a 1.5-kg moving mass, maximum tracking errors of plusmn0.5 mm for a 1-Hz sine wave trajectory, and steady-state errors within plusmn0.05 mm for an S-curve trajectory were achieved.
TL;DR: In this paper, a boundary controller based on Lyapunov's direct method and the backstepping technique is proposed to reduce transverse motion of flexible marine risers driven by a hydraulic system at the top end of the risers under environmental disturbances induced by waves, wind, and ocean currents.
TL;DR: The main goals of the design are a high level of actuator integration in order to minimize weight and volume, fault tolerance, and high reliability.
Abstract: This paper looks at the requirements and challenges of designing a permanent-magnet (PM) motor for a directly driven electromechanical actuator for aerospace applications. Having a directly driven system, the intermediate gearbox is eliminated, bringing advantages in terms of lower component count and reduced jamming probability. The design of a low-speed high pole number PM motor will be investigated as a potential solution. The main goals of the design are a high level of actuator integration in order to minimize weight and volume, fault tolerance, and high reliability. The design will be tailored to the requirements of a typical midspoiler actuation system for a large civil aircraft.
TL;DR: A novel electro-active polymer actuator employing the ionic networking membrane of poly(styrene-alt-maleimide) (PSMI)-incorporated poly(vinylidene fluoride) (PVDF) was developed to improve the electrical and mechanical performance of the artificial muscles as discussed by the authors.
Abstract: A novel electro-active polymer actuator employing the ionic networking membrane of poly(styrene-alt-maleimide) (PSMI)-incorporated poly(vinylidene fluoride) (PVDF) was developed to improve the electrical and mechanical performance of the artificial muscles. The main drawback of the previous ionic polymer-metal composite actuator was the straightening-back and relaxation under the constant voltage excitation. The present ionic networking membrane actuator overcomes the relaxation of the ionic polymer-metal composite actuator under the constant voltage and also shows much larger tip displacement than that of the Nafion-based actuator. Under the simple harmonic stimulus, the measured mechanical displacement was comparable to that of the Nafion-based actuator. The excellent electromechanical response of the current polymer actuator is attributed to two factors: the inherent large ionic-exchange capacity and the unique hydrophilic nano-channels of the ionic networking membrane. The electro-active polymer actuator of PSMI-incorporated PVDF can be a promising smart material and may possibly diversify niche applications in biomimetic motion.
TL;DR: A new model for shape memory alloy (SMA) actuators based on the physics of the process is described and control strategies using the model are developed, showing fast and accurate control of the strain in the SMA actuator.
Abstract: This brief describes a new model for shape memory alloy (SMA) actuators based on the physics of the process and develops control strategies using the model. The model consists of three equations - the temperature dynamics described by Joules heating-convectional cooling, the mole fraction distribution with temperature given by statistics to describe a two state system, and a constitutive equation relating the changes in temperature and mole fraction to the stress and strain induced in the SMA. This model is used to develop two control schemes for controlling the strain in an SMA actuator. The first control scheme describes a gain-scheduled proportional-integral (PI) controller, the gains of which are obtained by means of linear quadratic regulator (LQR) optimization. The second control scheme is an Hinfin loop-shaping controller using normalized coprime stabilization which ensures robust stability by minimizing the effect of unmodeled dynamics at high frequencies. Simulation and experimental results show fast and accurate control of the strain in the SMA actuator for both control schemes.
TL;DR: In this article, a 3DOF spherical actuator consisting of a ball-shaped rotor with a full circle of permanent magnet (PM) poles and a spherical-shell-like stator with two layers of circumferential air-core coils is proposed.
Abstract: This paper has proposed a 3-DOF spherical actuator consisting of a ball-shaped rotor with a full circle of permanent- magnet (PM) poles and a spherical-shell-like stator with two layers of circumferential air-core coils. One key feature of this design is the parametrization of PM and coil poles. Based on the torque model of the PM spherical actuator, the relationship between poles' parameters and torque output can be demonstrated. As a result, the actuator design aiming at achieving maximum torque output can be carried out from the relationships. Another advantage of this spherical actuator is its singularity-free workspace, which is verified with the actuator torque model and condition numbers.
TL;DR: In this article, a novel morphing structure concept is studied using non-linear finite element analysis (FEA), where Bi-stable asymmetrical laminates can be snapped between two geometries through a buckling mechanism that is activated by an applied load.
TL;DR: In this paper, the design, optimization, and commutation of a six-degree-of-freedom planar actuator with an active magnetic bearing is discussed, and several topologies are compared.
Abstract: This paper concerns the design, optimization, and commutation of a six-degree-of-freedom planar actuator with an active magnetic bearing. The planar motor has a stationary coil array and a translator with a Halbach magnet array. During movements in the plane, the set of energized coils changes with the position of the translator. In this paper, a method for the electromagnetic design of this type of actuator is discussed, and several topologies are compared. The best performing topology in terms of power dissipation and force and torque ripples has been manufactured and successfully tested.
Patent•
04 Nov 2008TL;DR: In this paper, a method for controlling a powertrain system includes controlling a first power actuator based upon a set of power constraints for the first actuator, and then controlling the second power actuators based upon the set of constraints of the second actuator.
Abstract: A method for controlling a powertrain system includes controlling a first power actuator based upon a set of power constraints for the first power actuator. The method further includes controlling a second power actuator based upon the set of power constraints for the second power actuator.
TL;DR: In this article, a curved pneumatic muscle based rotary actuator for the wearable elbow exoskeleton with joint torque control is proposed, which weakens coupling relationship between the output torque/force and contacting displacement of the PMA.
Patent•
04 Feb 2008TL;DR: In this article, the authors describe a haptic feedback system that includes a controller, a memory coupled to the controller, an actuator drive circuit coupled with the controller and a controller coupled with a memory.
Abstract: A haptic feedback system that includes a controller, a memory coupled to the controller, an actuator drive circuit coupled to the controller, and an actuator coupled to the actuator drive circuit. The memory stores at least one haptic effect that is executed by the controller in order to create a haptic effect.
TL;DR: In this paper, a nonlinear controller for an active heave compensation system using an electro-hydraulic system driven by a double rod actuator is presented, which reduces the effect of the heave motion of the vessel on the response of the riser by regulating the distance from the upper end of the Riser to the seabed.
TL;DR: In this paper, a parametrical analysis with magnetic simulation of a magnetostrictive actuator has been presented, and the performance has been evaluated on an experimental rig with an 8mm diameter Terfenol-D shaft.
Abstract: Several advanced technologies are introduced in automotive applications. Higher energy density and dynamic performance are demanding new and cost-effective actuator structures. Magnetostriction (MS), change in shape of materials under the influence of an external magnetic field, is one of the advanced technologies. Good understanding of specific design constrains is required to define and optimize a magnetostrictive actuator. This paper presents parametrical analysis with magnetic simulation of a magnetostrictive actuator. Proposed actuator has been designed, and the performance has been evaluated on experimental rig. Strain, elongation of the shaft, of 1000 ppm at 10 A and a blocked force over 4500 N has been achieved with shaft of 8 mm diameter, made of Terfenol- D . Furthermore, the effect of pre-stress of the Terfenol- D shaft has been evaluated experimentally. The study shows that excellent features can be obtained by magnetostrictive materials for many advanced applications.