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Actuators
Kinds of Actuators Terms modified by Actuators Selected AbstractsNonlinear Modeling and Tracking Control of a Hydraulic Rotary Vane ActuatorPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005Frank Heidtmann Rotary vane actuators as rotational drives provide rotational movements directly because they are constructed as a joint and actuator in one. So it is possible to pass on the disadvantageous transmission kinematics used with the so far usual differential cylinders at the arms of large manipulators. However, the use of hydraulic rotary vane actuators is associated with high internal oil leakage and/or high friction. Therefore, a nonlinear dynamic model for such an actuator, driving a rigid robot arm, as well as its nonlinear control are derived. To achieve tracking control a model based control law is set up using fundamental linear differential equations for the tracking error. The control law is implemented and tested on a testbed, the produced experimental results are presented. The same control algorithm can also be used to realize nonlinear disturbance attenuation for hydraulic rotary vane actuators via tracking control. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Design and Control of a Pneumatic Hybrid ActuatorPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005M. Dhanu Singh To simulate arbitrary force/displacement relationships, a hybrid actuator consisting of a .uidic muscle and a linear pressure spring is presented. Fluidic Muscles are interesting in their use as actuators in robotics, since they have a high power/weight ratio, a slip-stick free motion and a long durability. The operating point is de.ned as the half contracted-stroke of the muscle. The present paper describes a procedure to simulate virtual stiffness of a linear actuator by choosing an operating point of the pre-stressed muscle and applying PID Control to produce desired forces as function of state. The results are presented for a testbed. It is shown how the aforementioned control scheme produces a rapid and .exible stiffnes simulation. The device can be employed for later use in general environments such as motion simulations. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development of a Closed Air Loop Electropneumatic Actuator for Driving a Pneumatic Blood PumpARTIFICIAL ORGANS, Issue 8 2009Gi Seok Jeong Abstract In this study, we developed a small pneumatic actuator that can be used as an extracorporeal biventricular assist device. It incorporated a bellows-transforming mechanism to generate blood-pumping pressure. The cylindrical unit is 88 ± 0.1 mm high, has a diameter of 150 ± 0.1 mm, and weighs 2.4 ± 0.01 kg. In vitro, maximal outflow at the highest pumping rate (PR) exceeded 8 L/min when two 55 mL blood sacs were used under an afterload pressure of 100 mm Hg. At a pumping rate of 100 beats per minute (bpm), maximal hydraulic efficiency was 9.34% when the unit supported a single ventricle and 13.8% when it supported both ventricles. Moreover, pneumatic efficiencies of the actuator were 17.3% and 33.1% for LVAD and BVAD applications, respectively. The energy equivalent pressure was 62.78,208.10 mm Hg at a PR of 60,100 bpm, and the maximal value of dP/dt during systole was 1269 mm Hg/s at a PR of 60 bpm and 979 mm Hg/s at a PR of 100 bpm. When the unit was applied to 15 calves, it stably pumped 3,4 L/min of blood at 60 bpm, and no mechanical malfunction was experienced over 125 days of operation. We conclude that the presently developed pneumatic actuator can be utilized as an extracorporeal biventricular assist device. [source] Approximation and complexity trade-off by TP model transformation in controller design: A case study of the TORA system,ASIAN JOURNAL OF CONTROL, Issue 5 2010Zoltán Petres Abstract The main objective of the paper is to study the approximation and complexity trade-off capabilities of the recently proposed tensor product distributed compensation (TPDC) based control design framework. The TPDC is the combination of the TP model transformation and the parallel distributed compensation (PDC) framework. The Tensor Product (TP) model transformation includes an Higher Order Singular Value Decomposition (HOSVD)-based technique to solve the approximation and complexity trade-off. In this paper we generate TP models with different complexity and approximation properties, and then we derive controllers for them. We analyze how the trade-off effects the model behavior and control performance. All these properties are studied via the state feedback controller design of the Translational Oscillations with an Eccentric Rotational Proof Mass Actuator (TORA) System. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] Contraction Process of an Electroactive Actuator Based on a One Microsecond Atomistic Molecular Dynamics SimulationCHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2007David Zanuy Dr. Abstract The contraction process of an electroactive actuator constituted by calix[4]arene units and quaterthiophene segments has been investigated at the microscopic level by using atomistic molecular dynamics simulations in dichloromethane solution using explicit solvent molecules. Results derived from a 1,,s trajectory of the oxidized and deprotonated actuator indicate that the contraction occurs through a non-concerted mechanism in which each actuating units present in the system behave independently. The efficiency of the contraction process can be reduced by the presence of secondary conformational transitions in the calix[4]arene scaffolds. Accordingly, the drastic reduction of the molecular length expected during the contraction process can be limited by such transitions, which involve the rotational isomerism of a phenolate ring. However, such type of conformational transitions does not compromise the actuator power due to its intrinsic capacity to adopt compact molecular arrangements. On the other hand, the rate of the contraction process is influenced by the presence of solvent molecules, which have been found to reduce it by a factor of about 1000. [source] Carbon Nanotubes: High Electromechanical Response of Ionic Polymer Actuators with Controlled-Morphology Aligned Carbon Nanotube/Nafion Nanocomposite Electrodes (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Mater. Abstract Recent advances in fabricating controlled-morphology vertically aligned carbon nanotubes (VA-CNTs) with ultrahigh volume fraction create unique opportunities for markedly improving the electromechanical performance of ionic polymer conductor network composite (IPCNC) actuators. Continuous paths through inter-VA-CNT channels allow fast ion transport, and high electrical conduction of the aligned CNTs in the composite electrodes lead to fast device actuation speed (>10% strain/second). One critical issue in developing advanced actuator materials is how to suppress the strain that does not contribute to the actuation (unwanted strain) thereby reducing actuation efficiency. Here, experiments demonstrate that the VA-CNTs give an anisotropic elastic response in the composite electrodes, which suppresses the unwanted strain and markedly enhances the actuation strain (>8% strain under 4 V). The results reported here suggest pathways for optimizing the electrode morphology in IPCNCs using ultrahigh volume fraction VA-CNTs to further enhanced performance. [source] High Electromechanical Response of Ionic Polymer Actuators with Controlled-Morphology Aligned Carbon Nanotube/Nafion Nanocomposite ElectrodesADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Sheng Liu Abstract Recent advances in fabricating controlled-morphology vertically aligned carbon nanotubes (VA-CNTs) with ultrahigh volume fraction create unique opportunities for markedly improving the electromechanical performance of ionic polymer conductor network composite (IPCNC) actuators. Continuous paths through inter-VA-CNT channels allow fast ion transport, and high electrical conduction of the aligned CNTs in the composite electrodes lead to fast device actuation speed (>10% strain/second). One critical issue in developing advanced actuator materials is how to suppress the strain that does not contribute to the actuation (unwanted strain) thereby reducing actuation efficiency. Here, experiments demonstrate that the VA-CNTs give an anisotropic elastic response in the composite electrodes, which suppresses the unwanted strain and markedly enhances the actuation strain (>8% strain under 4 V). The results reported here suggest pathways for optimizing the electrode morphology in IPCNCs using ultrahigh volume fraction VA-CNTs to further enhanced performance. [source] High Breakdown Field Dielectric Elastomer Actuators Using Encapsulated Polyaniline as High Dielectric Constant FillerADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Martin Molberg Abstract A novel method allowing rapid production of reliable composites with increased dielectric constant and high dielectric strength for dielectric elastomer actuators (DEA) is reported. The promising approach using composites of conductive particles and insulating polymers generally suffers from low breakdown fields when applied to DEA devices. The present publication shows how to overcome this deficiency by using conductive polyaniline (PANI) particles encapsulated into an insulating polymer shell prior to dispersion. PANI particles are encapsulated using miniemulsion polymerization (MP) of divinylbenzene (DVB). The encapsulation process is scaled up to approximately 20 g particles per batch. The resulting particles are used as high dielectric constant (,,) fillers. Composites in a polydimethylsiloxane (PDMS) matrix are prepared and the resulting films characterized by dielectric spectroscopy and tensile tests, and evaluated in electromechanical actuators. The composite films show a more than threefold increase in ,,, breakdown field strengths above 50 V ,m,1, and increased strain at break. These novel materials allow tuning the actuation strain or stress output and have potential as materials for energy harvesting. [source] A Continuous Flow Synthesis of Micrometer-Sized Actuators from Liquid Crystalline ElastomersADVANCED MATERIALS, Issue 47 2009Christian Ohm We demonstrate the use of a microfluidic setup to prepare monodisperse and spherical beads from a liquid crystalline elastomer. These particles show a strong and reversible shape change into a cigar-like conformation during the transition into the isotropic phase. These properies are a result of the monodomainic alignment of the mesogens in the flow field of the microfluidic setup. [source] Fault-Tolerant Dielectric Elastomer Actuators using Single-Walled Carbon Nanotube Electrodes,ADVANCED MATERIALS, Issue 3 2008W. Yuan Fault-tolerant actuators. Single-walled carbon nanotubes were studied as new compliant electrodes for dielectric elastomers. The spray-coated SWNT electrodes drive electromechanical strains greater than 200,%. When a fault is present due to pin puncture or internal defect in the elastomer films, dielectric breakdown causes localized self-clearing of the SWNT electrodes and isolation of the fault. The increased fault tolerance may enhance the actuation reliability of dielectric elastomers actuators. [source] Study of the Different Types of Actuators and Mechanisms for Upper Limb ProsthesesARTIFICIAL ORGANS, Issue 6 2003Vanderlei O. Del Cura Abstract: Research in the area of actuators and mechanisms has shown steadily growing technological advances in externally activated upper limb prostheses. From among the actuators, advances include the use of piezoelectric materials, special metal alloys, polymers, and new motor applications, while the advances in mechanisms include mechanical designs based on the anatomy of the human hand and improvements in the way these components are combined. These efforts are aimed at meeting the need for anthropomorphic and functional prosthetic devices that enable patients to carry out basic daily tasks more easily and reduce the rejection rate of prostheses. This article technically discusses the several types of actuators and mechanisms, listing their main characteristics, applications, and advantages and disadvantages, and the current state of research in the area of rehabilitation of upper limb functions through the use of active prostheses. Comparisons of these devices are made with regard to the main criteria of construction and operation required to achieve optimal prosthetic performance. [source] Polymeric Actuators for Biological ApplicationsCHEMPHYSCHEM, Issue 12 2007Avishay Pelah Dr. Abstract To shed light on the role of cell rheology and mechanotransduction in various physiological and disease states, different techniques of force application, such as optical tweezers and deformable substrates, are employed. In this present paper we describe a new approach for the deformation of cells based on the temperature-sensitive polymer poly(N-isopropylacrylamide), PNIPAM. In response to temperature changes, PNIPAM gels undergo extensive and reversible changes in volume that allow them to be used as actuators for stretching and compressing cells and tissues. Herein we focus mainly on our experience with the deformation of red blood cells as proof of principle, and demonstrate the wealth of possibilities such stimuli-responsive materials may offer as actuators. [source] Design of an MR-compatible piezoelectric actuator for MR elastographyCONCEPTS IN MAGNETIC RESONANCE, Issue 4 2002Kai Uffmann Abstract Magnetic Resonance (MR) elastography is a method for measuring tissue elasticity via phase images acquired with an MR scanner. The propagation of periodic mechanical waves through the tissue can be captured by means of a modified phase contrast sequence. These waves are generated with a mechanical oscillator (actuator) and coupled into the tissue through the skin. The actuator must be capable of generating a sinusoidal excitation with excellent phase and amplitude stability, while not disturbing the MR imaging process. In this work, an actuator based on a piezoelectric principle was developed. Based on the imaging evaluation of several material samples, the housing for the piezoelectric ceramic was constructed of aluminum. Smaller parts of the housing were manufactured from brass and titanium to fulfill the mechanical constraints. A lever was used to transfer the oscillation generated by the piezoelectric ceramic to the point of excitation. The lever amplifies the piezoelectric motion, allowing for a more compact design. Three different lever designs were characterized by an acceleration sensor both outside and inside the magnet. It was shown that the rigidity of the lever, as determined by its material and form, was decisive in determining the resonant frequency of the system and therefore the maximum practical frequency of operation. It was also shown that the motion of the oscillator is unaffected by the electromagnetic fields of the MR imager. The final design can be placed directly in the magnet bore within a few centimeters of the tissue volume to be imaged without generating significant artifacts. An amplitude range of 0,1 mm in the frequency range from 0 to over 300 Hz was achieved, sufficient for performing most MR elastography applications. © 2002 Wiley Periodicals, Inc. Concepts in Magnetic Resonance (Magn Reson Engineering) 15: 239,254, 2002 [source] Recent Progress in Dielectric Barrier Discharges for Aerodynamic Flow ControlCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-2 2007G. I. Font Abstract Plasma actuators are electrical devices that use an atmospheric pressure dielectric barrier discharge for flow control. They have been employed successfully to promote boundary layer attachment. Simulations have been carried out of a plasma actuator using Direct-Simulation-Monte-Carlo and Particle-in-Cell methods. This work summarizes some recent results including: 1) the method by which force is imparted by the actuator to the neutral flow, 2) the effect of electronegative gasses, such as oxygen, and 3) the effects on the neutral flow of the plasma force. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Real-time hybrid testing using the unconditionally stable explicit CR integration algorithmEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2009Cheng Chen Abstract Real-time hybrid testing combines experimental testing and numerical simulation, and provides a viable alternative for the dynamic testing of structural systems. An integration algorithm is used in real-time hybrid testing to compute the structural response based on feedback restoring forces from experimental and analytical substructures. Explicit integration algorithms are usually preferred over implicit algorithms as they do not require iteration and are therefore computationally efficient. The time step size for explicit integration algorithms, which are typically conditionally stable, can be extremely small in order to avoid numerical stability when the number of degree-of-freedom of the structure becomes large. This paper presents the implementation and application of a newly developed unconditionally stable explicit integration algorithm for real-time hybrid testing. The development of the integration algorithm is briefly reviewed. An extrapolation procedure is introduced in the implementation of the algorithm for real-time testing to ensure the continuous movement of the servo-hydraulic actuator. The stability of the implemented integration algorithm is investigated using control theory. Real-time hybrid test results of single-degree-of-freedom and multi-degree-of-freedom structures with a passive elastomeric damper subjected to earthquake ground motion are presented. The explicit integration algorithm is shown to enable the exceptional real-time hybrid test results to be achieved. Copyright © 2008 John Wiley & Sons, Ltd. [source] Compensation of actuator delay and dynamics for real-time hybrid structural simulationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2008M. Ahmadizadeh 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. Copyright © 2007 John Wiley & Sons, Ltd. [source] Equivalent force control method for generalized real-time substructure testing with implicit integrationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2007Bin Wu Abstract This paper presents a new method, called the equivalent force control method, for solving the nonlinear equations of motion in a real-time substructure test using an implicit time integration algorithm. The method replaces the numerical iteration in implicit integration with a force-feedback control loop, while displacement control is retained to control the motion of an actuator. The method is formulated in such a way that it represents a unified approach that also encompasses the effective force test method. The accuracy and effectiveness of the method have been demonstrated with numerical simulations of real-time substructure tests with physical substructures represented by spring and damper elements, respectively. The method has also been validated with actual tests in which a Magnetorheological damper was used as the physical substructure. Copyright © 2007 John Wiley & Sons, Ltd. [source] Hybrid platform for vibration control of high-tech equipment in buildings subject to ground motion.EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2003Part 1: experiment Abstract This paper presents an experimental study, while a companion paper addresses an analytical study, to explore the possibility of using a hybrid platform to mitigate vibration of a batch of high-tech equipment installed in a building subject to nearby traffic-induced ground motion. A three-storey building model and a hybrid platform model are designed and manufactured. The hybrid platform is mounted on the building floor through passive mounts composed of leaf springs and oil dampers and controlled actively by an electromagnetic actuator with velocity feedback control strategy. The passive mounts are designed in such a way that the stiffness and damping ratio of the platform can be changed. A series of shaking table tests are then performed on the building model without the platform, with the passive platform of different parameters, and with the hybrid platform. The experimental results demonstrate that the hybrid platform is very effective in reducing the velocity response of a batch of high-tech equipment in the building subject to nearby traffic-induced ground motion if dynamic properties of the platform and control feedback gain are selected appropriately. Copyright © 2003 John Wiley & Sons, Ltd. [source] Long-span seek control system for hard disk drive without mode-switchingELECTRICAL ENGINEERING IN JAPAN, Issue 3 2010Shinji Takakura Abstract In hard disk drives (HDD) there are two control modes: the head positioning control mode and the other is the seek control mode. In the head positioning control mode, a feedback controller is optimally designed to suppress disturbances. In the long-span seek mode, a velocity feedback control system is applied in order to move the heads fast. Thus, an HDD has multiple control systems, and the head is moved to the target position while changing from one control system to the other. However, changing the control system causes a discontinuous control signal, which activates the resonant mode of an actuator. Past methods can only decrease discontinuous control, and therefore a single control system that can be used for both a seek control mode and a head positioning control mode is necessary for a narrow track pitch. In the proposed method, the feedback controller is decomposed into an integrator and a phase compensator. The VCM model is updated by the output of the phase compensator, and the integrator and the output of the velocity feedback controller control the VCM. The validity of the proposed method was confirmed by numerical and experimental results using a miniature 2.5-inch hard disk drive. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 51,60, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20935 [source] Precise disturbance modeling for improvement of positioning performanceELECTRICAL ENGINEERING IN JAPAN, Issue 2 2010Masafumi Yamamoto Abstract This paper presents a modeling methodology for unknown disturbances in mechatronics systems, based on disturbance estimation using an iterative learning process. In disturbance modeling, nonlinear frictions are specially handled as disturbances in the mechanisms, which mainly degrade trajectory control performance. Friction can be mathematically modeled by using learned estimation data as a function of the displacement, velocity. acceleration, and jerk of the actuator. This model has the distinctive feature that friction compensation can be achieved with a generalization capability for different conditions. The proposed positioning control approach with disturbance modeling and compensation has been verified by experiments using a table drive system on a machine stand. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(2): 31,39, 2010; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/eej.20928 [source] Development of an electrohydraulic total artificial heart system: Improvement of pump unitELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 9 2010Akihiko Homma Abstract An electrohydraulic total artificial heart (EHTAH) system has been developed. The EHTAH system consists of diaphragm-type blood pumps, and electrohydraulic actuator, an internal control unit, a transcutaneous energy transfer system (TETS), a transcutaneous optical telemetry system (TOTS), and an internal battery. The reciprocating rotation of the impeller generates oil pressure that drives the blood pumps at alternating intervals. The blood pumps and the actuator were successfully integrated into the pump unit without oil conduits. As a result of miniaturizing the blood pumps and the actuator, the displacement volume and weight of the EHTAH system were decreased to 872 ml and 2492 g, respectively. Furthermore, the maximum flow rate and efficiency increased up to 12 L/min and 15.4%. The pump units and the EHTAH systems were successfully implanted in 36 calves weighing from 55 to 87 kg. In the longest case, a calf with the pump unit survived for 87 days and a calf with the EHTAH system survived for 70 days. The EHTAH system was powered by the TETS, and was powered every day by the internal battery for 40 minutes. These results indicate that the EHTAH system has the potential to become a fully implantable cardiac replacement system. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(9): 34,46, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10220 [source] High-Speed and Wide-Angle Deflection Optical MEMS Scanner Using Piezoelectric ActuationIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2010Takayuki Iseki Member Abstract A fast and wide deflection silicon-resonant torsional optical scanner driven by a piezoelectric actuator has been developed and patented. The scanner is composed of a 1-mm square mirror and two pairs of torsion beams and arms fabricated using microelectromechanical system (MEMS) processing of a silicon-on-insulator (SOI) wafer. According to calculations, at the same resonant driving frequency, the maximum principal stress of this structure was about one-third smaller than that of the usual structure having one pair of torsion beams. We achieved high frequency scanning of the optical beam with a large angular deflection up to 54° at 38 kHz with a 5 V peak-to-peak applied voltage using the bulk piezoelectric stack actuator, and up to 17° at 38 kHz with a 25 V peak-to-peak voltage using the unimorph actuator of a zinc oxide (ZnO) thin film. These results show that this scanner has the ability to perform the horizontal scanning for high-resolution extended graphics array (XGA) or super extended graphics array (SXGA) laser display. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Buckled Bridges Using Film Stress for Three-Dimensional Structures: Effects of Lateral Designs on Vertical Profiles and Dynamic CharacteristicsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2010Minoru Sasaki Member Abstract Bridges buckled by film stress can generate a vertical displacement resulting in three-dimensional structures. We have demonstrated a micromirror lifted by buckled bridges and a vertical comb drive actuator. The structures show rounded profiles in a stable manner. The detailed profiles of the bridges and the lifted micromirrors are examined. The relations between the lateral design and its effect on the vertical profile and the dynamic characteristics are studied. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Artifical Muscles: Nanocomposite Hydrogel with High Toughness for Bioactuators (Adv. Mater.ADVANCED MATERIALS, Issue 17 200917/2009) The inside cover shows a nanofibrous hydrogel based on ferritin for a bioinspired nanocomposite actuator, reported in work by Seon Jeong Kim and co-workers on p. 1712. The ferritin-based nanofibrous hydrogels demonstrate synergy between the ferritin protein and a synthetic polymer matrix, as the protein shell of ferritin behaves like an elastic nanospring in the polymer. The actuator is reversibly actuated by chemical energy under external tensile stress, showing improved response speed in comparison to bulk and microfiber hydrogels, coming closer to the goal of mimicking the performance of natural muscle. [source] Nanocomposite Hydrogel with High Toughness for BioactuatorsADVANCED MATERIALS, Issue 17 2009Min Kyoon Shin Ferritin-based nanofibrous hydrogels that demonstrate synergy between the ferritin protein and the synthetic polymer matrix are fabricated. The hybrid hydrogels showed enhanced mechanical properties and repeated expansion and contraction without showing severe creep during pH switching. The ferritin nanoparticles incorporated into the hydrogel nanofibers improved the actuation stability of a hydrogel actuator by acting as elastic nanosprings in a nanoscale polymer. [source] Optoelectrothermic Control of Highly Integrated Polymer-Based MEMS Applied in an Artificial SkinADVANCED MATERIALS, Issue 9 2009Andreas Richter A large-scale integration technology for MEMS based on the optoelectrothermic control of a temperature-sensitive hydrogel is described and exemplified using an imaging array system, a so-called artificial skin. The hydrogel itself acts as active functional unit, i.e., as actuator. The artificial skin comprises more than 4,000 individual actuators and provides both, visual and palpable artificial impressions of a surface. [source] A three-dimensional model describing stress-temperature induced solid phase transformations: solution algorithm and boundary value problemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2004Ferdinando Auricchio Abstract An always increasing knowledge on material properties as well as a progressively more sophisticated production technology make shape memory alloys (SMA) extremely interesting for the industrial world. At the same time, SMA devices are typically characterized by complex multi-axial stress states as well as non-homogeneous and non-isothermal conditions both in space and time. This aspect suggests the finite element method as a useful tool to help and improve application design and realization. With this aim, we focus on a three-dimensional macroscopic thermo-mechanical model able to reproduce the most significant SMA features (Int. J. Numer. Methods Eng. 2002; 55: 1255,1264), proposing a simple modification of such a model. However, the suggested modification allows the development of a time-discrete solution algorithm, which is more effective and robust than the one previously discussed in the literature. We verify the computational tool ability to simulate realistic mechanical boundary value problems with prescribed temperature dependence, studying three SMA applications: a spring actuator, a self-expanding stent, a coupling device for vacuum tightness. The effectiveness of the model to solve thermo-mechanical coupled problems will be discussed in a forthcoming work. Copyright © 2004 John Wiley & Sons, Ltd. [source] Robust diagnosis and fault-tolerant control of distributed processes over communication networksINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2009Sathyendra Ghantasala Abstract This paper develops a robust fault detection and isolation (FDI) and fault-tolerant control (FTC) structure for distributed processes modeled by nonlinear parabolic partial differential equations (PDEs) with control constraints, time-varying uncertain variables, and a finite number of sensors that transmit their data over a communication network. The network imposes limitations on the accuracy of the output measurements used for diagnosis and control purposes that need to be accounted for in the design methodology. To facilitate the controller synthesis and fault diagnosis tasks, a finite-dimensional system that captures the dominant dynamic modes of the PDE is initially derived and transformed into a form where each dominant mode is excited directly by only one actuator. A robustly stabilizing bounded output feedback controller is then designed for each dominant mode by combining a bounded Lyapunov-based robust state feedback controller with a state estimation scheme that relies on the available output measurements to provide estimates of the dominant modes. The controller synthesis procedure facilitates the derivation of: (1) an explicit characterization of the fault-free behavior of each mode in terms of a time-varying bound on the dissipation rate of the corresponding Lyapunov function, which accounts for the uncertainty and network-induced measurement errors and (2) an explicit characterization of the robust stability region where constraint satisfaction and robustness with respect to uncertainty and measurement errors are guaranteed. Using the fault-free Lyapunov dissipation bounds as thresholds for FDI, the detection and isolation of faults in a given actuator are accomplished by monitoring the evolution of the dominant modes within the stability region and declaring a fault when the threshold is breached. The effects of network-induced measurement errors are mitigated by confining the FDI region to an appropriate subset of the stability region and enlarging the FDI residual thresholds appropriately. It is shown that these safeguards can be tightened or relaxed by proper selection of the sensor spatial configuration. Finally, the implementation of the networked FDI,FTC architecture on the infinite-dimensional system is discussed and the proposed methodology is demonstrated using a diffusion,reaction process example. Copyright © 2008 John Wiley & Sons, Ltd. [source] Neural network-based adaptive control of piezoelectric actuators with unknown hysteresisINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2009Wen-Fang Xie Abstract This paper proposes a neural network (NN)-based adaptive control of piezoelectric actuators with unknown hysteresis. Based on the classical Duhem model described by a differential equation, the explicit solution to the equation is explored and a new hysteresis model is constructed as a linear model in series with a piecewise continuous nonlinear function. An NN-based dynamic pre-inversion compensator is designed to cancel out the effect of the hysteresis. With the incorporation of the pre-inversion compensator, an adaptive control scheme is proposed to have the position of the piezoelectric actuator track the desired trajectory. This paper has three distinct features. First, it applies the NN to online approximate complicated piecewise continuous unknown nonlinear functions in the explicit solution to Duhem model. Second, an observer is designed to estimate the output of hysteresis of piezoelectric actuator based on the system input and output. Third, the stability of the controlled piezoelectric actuator with the observer is guaranteed. Simulation results for a practical system validate the effectiveness of the proposed method in this paper. Copyright © 2008 John Wiley & Sons, Ltd. [source] Nonlinear reference tracking control of a gas turbine with load torque estimationINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2008B. Pongrácz Abstract Input,output linearization-based adaptive reference tracking control of a low-power gas turbine model is presented in this paper. The gas turbine is described by a third-order nonlinear input-affine state-space model, where the manipulable input is the fuel mass flowrate and the controlled output is the rotational speed. The stability of the one-dimensional zero dynamics of the controlled plant is investigated via phase diagrams. The input,output linearizing feedback is extended with a load torque estimator algorithm resulting in an adaptive feedback scheme. The tuning of controller parameters is performed considering three main design goals: appropriate settling time, robustness against environmental disturbances and model parameter uncertainties, and avoiding the saturation of the actuator. Simulations show that the closed-loop system is robust with respect to the variations in uncertain model and environ-mental parameters and its performance satisfies the defined requirements. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||||||||