Showing papers on "Actuator published in 2010"

Dielectric Barrier Discharge Plasma Actuators for Flow Control

Abstract: The term plasma actuator has now been a part of the fluid dynamics flow-control vernacular for more than a decade. A particular type of plasma actuator that has gained wide use is based on a single–dielectric barrier discharge (SDBD) mechanism that has desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control is through a generated body-force vector field that couples with the momentum in the external flow. The body force can be derived from first principles, and the effect of plasma actuators can be easily incorporated into flow solvers so that their placement and operation can be optimized. They have been used in a wide range of internal and external flow applications. Although initially considered useful only at low speeds, plasma actuators are effective in a number of applications at high subsonic, transonic, and supersonic Mach numbers, owing largely to more optimized actuator designs that were developed through better understanding and modeling of...

Surgical system instrument sterile adapter

Abstract: A sterile adapter, a drape including the adapter, and a method of draping a manipulator arm are provided. In one embodiment, the sterile adapter includes a housing configured to receive a distal face of an instrument manipulator having a plurality of manipulator actuator outputs, and a membrane interface disposed at a distal end of the housing, the membrane interface including a plurality of actuator interfaces. The adapter further includes a pair of supports coupled to the housing, the pair of supports configured to retain a surgical instrument having a plurality of instrument actuator inputs so that the plurality of instrument actuator inputs are positioned opposite to corresponding manipulator actuator outputs with an actuator interface between each corresponding instrument actuator input and manipulator actuator output.

Vehicle Control System

Abstract: A vehicle control system which can ensure high reliability, real-time processing, and expandability with a simplified ECU configuration and a low cost by backing up an error through coordination in the entire system without increasing a degree of redundancy of individual controllers beyond the least necessary level. The vehicle control system comprises a sensor controller for taking in sensor signals indicating a status variable of a vehicle and an operation amount applied from a driver, a command controller for generating a control target value based on the sensor signals taken in by the sensor controller, and an actuator controller for receiving the control target value from the command controller and operating an actuator to control the vehicle, those three controller being interconnected via a network. The actuator controller includes a control target value generating unit for generating a control target value based on the sensor signals taken in by the sensor controller and received by the actuator controller via the network when the control target value generated by the command controller is abnormal, and controls the actuator in accordance with the control target value generated by the control target value generating unit.

The high potential of shape memory alloys in developing miniature mechanical devices: A review on shape memory alloy mini-actuators

Abstract: Shape memory alloys (SMAs) are a well-known class of smart materials. When subjected to certain thermal cycles, they are able to generate mechanical work by recovering a predetermined shape. Due to their high mechanical performances, their compactness and lightness, SMAs can be easily included in mechanical devices of small dimensions and used as actuating elements. There are rather few companies worldwide that deal in SMA mini-actuators; we can find, nonetheless, quite a large number of studies about them. In this paper, we illustrate the state of art of SMA mini-actuators, in the meaning of mini-modular-mechanical devices activated by SMA materials; particular attention is granted to the commercial SMA mini-actuators and to the most recent and relevant publications and patents in this field. Ferromagnetic shape memory alloys are presented as well.

An Asymmetrically Surface-Modified Graphene Film Electrochemical Actuator

Abstract: It is critically important to develop actuator systems for diverse needs ranging from robots and sensors to memory chips. The advancement of mechanical actuators depends on the development of new materials and rational structure design. In this study, we have developed a novel graphene electrochemical actuator based on a rationally designed monolithic graphene film with asymmetrically modified surfaces. Hexane and O2 plasma treatment were applied to the opposite sides of graphene film to induce the asymmetrical surface properties and hence asymmetrical electrochemical responses, responsible for actuation behaviors. The newly designed graphene actuator demonstrated here opens a new way for actuator fabrication and shows the potential of graphene film for applications in various electromechanical systems.

The Actuator With Mechanically Adjustable Series Compliance

Abstract: Running is a complex dynamic task that places strict requirements on both the physical components and software-control systems of a robot. This paper explores some of those requirements and, in particular, explores how a variable-compliance actuation system can satisfy many of them. We present the mechanical design and software-control system for such an actuator system. We analyze its performance through simulation and bench-top experimental validation of a prototype version. In conclusion, we demonstrate, through simulation, the application of our proof-of-concept actuator to the problem of biped running.

A novel actuator with adjustable stiffness (AwAS)

Abstract: This paper describes the design and development of a new actuator with adjustable stiffness (AwAS) which can be used in robots which are necessary to work close to or physically interact with humans, e.g. humanoids and exoskeletons. The actuator presented in this work can independently control equilibrium position and stiffness by two motors. The first motor controls the equilibrium position while the second motor regulates the compliance. The novelty of the proposed design with respect to the existing systems is on the principle used to regulate the compliance. This is done not through the tuning of the pretension of the elastic element as in the majority of existing system but by controlling the fixation of the elastic elements (springs) using a linear drive. An important consequence of this approach is that the displacement needed to change the stiffness is perpendicular to the forces generated by the springs, thus this helps to minimize the energy/power required to change the stiffness. This permits the use of a small motor for the stiffness adjustment resulting in a lighter setup. Experimental results are presented to show the ability of AwAS to control position and regulate the stiffness independently.

Delay-Adaptive Predictor Feedback for Systems With Unknown Long Actuator Delay $ $

Abstract: Stabilization of an unstable system with an unknown actuator delay of substantial length is an important problem that has never been attempted. We present a Lyapunov-based adaptive control design, prove its stability and regulation properties for the plant and actuator states, and present a simulation example inspired by the problem of control of pitch and flight path rates in the unstable X-29 aircraft.

Nanopositioning System With Force Feedback for High-Performance Tracking and Vibration Control

Abstract: In this study, the actuator load force of a nanopositioning stage is utilized as a feedback variable to achieve both tracking and damping. The transfer function from the applied actuator voltage to the measured load force exhibits a zero-pole ordering that greatly simplifies the design and implementation of a tracking and damping controller. Exceptional tracking and damping performance can be achieved with a simple integral controller. Other outstanding characteristics include guaranteed stability and insensitivity to changes in resonance frequency. Experimental results on a high-speed nanopositioner demonstrate an increase in the closed-loop bandwidth from 210 Hz (with an integral controller) to 2.07 kHz (with a force-feedback control). Gain margin is simultaneously improved from 5 dB to infinity.

Wireless Sensor and Actuator Networks: Algorithms and Protocols for Scalable Coordination and Data Communication

Abstract: A mixture of theory, experiments, and simulations that provide qualitative and quantitative insights into the technology The important new technology of wireless sensor and actuator networks provides radically new communication and networking paradigms with many new applications. Wireless Sensor and Actuator Networks is a timely text that presents a fault-tolerant, reliable, low-latency, and energy-aware framework for wireless sensor and actuator networks, enabling readers to fulfill the ultimate goals of the applicationssuch as protecting critical infrastructures, achieving timely emergency responses, and monitoring the environment. Taking a problem-oriented approach, this resource discusses a wide range of computing and communication problems and solutions that arise in rapidly emerging wireless sensor and actuator networks, striking a balance between theory and practice. Discusses backbones as subsets of sensors or actuators that suffice for performing basic data communication operations or area sensing coverage Surveys existing data communication schemes (broadcasting, routing, multicasting, anycasting, geocasting) for sensor-actuator coordination Reviews the location service techniques Addresses the problem of energy-efficient data gathering by mobile sinks/actuators Describes protocols for coordination and topology control in sensor, actuator, and robot networks Reviews existing solutions to the sensor placement problem in wireless sensor and actuator networks This book is unique in that it addresses sensor and actuator networking in a comprehensive mannercovering all the aspects and providing up-to-date informationso that industry operators and academics from various areas can learn more about current networking trends, become aware of the possible architectures, and understand the advantages and limits in future commercial, social, and educational applications. Wireless Sensor and Actuator Networks is appropriate for graduate students in computer science, electrical engineering, and telecommunications, as well as practitioners working as engineers, programmers, and technologists.

Pinion Blade Drive Mechanism for a Laparoscopic Vessel Dissector

Abstract: A surgical instrument comprises a handle assembly including an actuator mounted for manipulation through an actuation stroke. An elongate shaft extends distally from the handle assembly and defines a longitudinal axis. A reciprocating member extends at least partially through the elongate shaft, and is mounted for longitudinal motion through the elongate shaft in response to manipulation of the actuator through the actuation stroke. A drive mechanism includes a first rotating component coupled to the actuator about a first circumference to induce rotational motion in the first rotating component. A second rotating component is coupled to the first rotating component such that rotational motion in the first rotating component induces rotational motion in the second rotating component. The second rotating component is coupled to the reciprocating member about a second circumference such that rotational motion of the second rotating component induces longitudinal motion in the reciprocating member. The second circumference is greater than the first circumference.

Technical Notes and Correspondence Delay-Adaptive Predictor Feedback for Systems With Unknown Long Actuator Delay

Abstract: Stabilization of an unstable system with an unknown actuator delay of substantial length is an important problem that has never been attempted. We present a Lyapunov-based adaptive control design, prove its stability and regulation properties for the plant and actuator states, and present a simulation example inspired by the problem of control of pitch and flight path rates in the unstable X-29 aircraft. Index Terms—Adaptive control, delay systems, distributed parameter systems.

Method of providing tactile feedback and apparatus

Abstract: A method includes detecting a query gesture and actuating, in response to the query gesture, an actuator to provide tactile feedback including information associated with the query gesture. The query gesture may be detected on a touch-sensitive display of a portable electronic device.

Design, analysis and simulation of magnetostrictive actuator and its application to high dynamic servo valve

Abstract: Flapper–nozzle type Electro Hydraulic Servo Valve (EHSV) operated by conventional torque motor actuators has been used in wide range of industrial applications. As their bandwidths are limited, they are not suitable for high-speed applications. The work presented in this paper deals with the mechatronic approach for the design of a magnetostrictive actuator with flexure amplifier and a magnetically biased magnetostrictive actuator for application in high frequency flapper–nozzle servo valve. A magnetostrictive actuator has been designed, built and integrated into an existing flapper–nozzle servo valve by replacing the torque motor. Incorporating the dynamics of the magnetostrictive actuator, the dynamics of the valve was simulated. Necessary parameters for the actuator have been arrived by finite element model. No load flow characteristics are analyzed and compared with experimental values. Step response has been compared with conventional valve. The results show that the valve has satisfactory static and dynamic characteristics for applications in high-speed actuation systems.

Frequency Self-tuning Scheme for Broadband Vibration Energy Harvesting

Abstract: The recent proliferation of microscale devices has raised the issue of energy harvesting for replacing batteries that present maintenance and recycling problems. Particularly, piezoelectric seismic microgenerators offer the advantages of easy maintenance and high power output, but are very sensitive to frequency drifts that can dramatically decrease their performance. The purpose of the present article is to expose a technique to ensure that the harvester resonance frequency matches the base motion frequency, without any external intervention. The principles of the proposed method rely on ultralow-cost frequency sensing combined with an energy-efficient stiffness tuning, through the use of an additional actuator. Experimental results carried out to validate the model show that such an approach permits increasing the effective bandwidth of the structure by a factor of 4 in terms of mechanical vibrations and having a 100% frequency band gain in terms of total power output of the device (i.e., taking into ac...

Method For Feeding Staples In a Low Profile Surgical Stapler

Abstract: A method for feeding a fastener including the step of providing a device having a housing, at least one fastener within the housing, wherein the fastener is disposed within the housing in a first plane, an elongated actuator disposed within the housing, the actuator comprising a shaft substantially parallel to a longitudinal axis of the housing and rigidly spaced from the fastener in a second plane the actuator comprising at least one radially extending advancer disposed along a length thereof. The method further includes the step of rotating the actuator so to engage the fastener, and longitudinally moving the actuator to advance the fastener.

Large Effective-Strain Piezoelectric Actuators Using Nested Cellular Architecture With Exponential Strain Amplification Mechanisms

Abstract: Design and analysis of piezoelectric actuators having over 20% effective strain using an exponential strain amplification mechanism are presented in this paper. Piezoelectric ceramic material, such as lead zirconate titanate (PZT), has large stress and bandwidth, but its extremely small strain, i.e., only 0.1%, has been a major bottleneck for broad applications. This paper presents a new strain amplification design, called a “nested rhombus” multilayer mechanism, that increases strain exponentially through its hierarchical cellular structure. This allows for over 20% effective strain. In order to design the whole actuator structure, not only the compliance of piezoelectric material but also the compliance of the amplification structures needs to be taken into account. This paper addresses how the output force and displacement are attenuated by the compliance involved in the strain amplification mechanism through kinematic and static analysis. An insightful lumped parameter model is proposed to quantify the performance degradation and facilitate design tradeoffs. A prototype-nested PZT cellular actuator that weighs only 15 g has produced 21% effective strain (2.5 mm displacement from 12-mm actuator length and 30 mm width) and 1.7 N blocking force.

Design, testing and control of a magnetorheological actuator for assistive knee braces

Abstract: This paper is aimed at developing a smart actuator for assistive knee braces to provide assistance to disabled or elderly people with mobility problems. A magnetorheological (MR) actuator is developed to be used in assistive knee braces to provide controllable torque. The MR actuator can work as a brake or a clutch. When active torque is needed, the DC motor works and the MR actuator functions as a clutch to transfer the torque generated by the motor to the leg; when passive torque is desired, the DC motor is turned off and the MR actuator functions as a brake to provide controllable passive torque. The prototype of the developed MR actuator is fabricated and experiments are carried out to investigate the characteristics of the MR actuator. The results show that the MR actuator is able to provide sufficient torque needed for normal human activities. Adaptive control is proposed for controlling the MR actuator. Anti-windup strategy is used to achieve better control performance. Experiments on the MR actuator under control are also performed to study the torque tracking ability of the system.

Method and apparatus for localization of haptic feedback

Abstract: In an embodiment, a haptic feedback system includes a plurality of actuators to provide tactile feedback associated with an input surface. Each actuator is adapted to be activated independently of the other actuators. The system further includes a controller to activate a first actuator of the plurality of actuators to induce a first vibration at a selected input location of the input surface and to activate one or more additional actuators to induce at least a second vibration to localize the first vibration at the selected input location.

Simple piezoelectric-actuated mirror with 180 kHz servo bandwidth.

Abstract: We present a high bandwidth piezoelectric-actuated mirror for length stabilization of an optical cavity. The actuator displays a transfer function with a flat amplitude response and greater than 135 masculine phase margin up to 200 kHz, allowing a 180 kHz unity gain frequency to be achieved in a closed servo loop. To the best of our knowledge, this actuator has achieved the largest servo bandwidth for a piezoelectric transducer (PZT). The actuator should be very useful in a wide variety of applications requiring precision control of optical lengths, including laser frequency stabilization, optical interferometers, and optical communications.

Design of a Large Range XY Nanopositioning System

Abstract: Achieving large motion range (> 1 mm) along with nanometric motion quality (< 10 nm), simultaneously, has been a key challenge in nanopositioning systems. Practical limitations associated with the individual physical components (flexure bearing, actuators, and sensors) and their integration, particularly in the case of multi-axis systems, have restricted the range of current nanopositioning systems to about 100 μm. This paper presents a novel physical system layout, with a parallel-kinematic XY flexure mechanism at its heart, that provides a high degree of decoupling between the two motion axes by avoiding geometric over-constraints, provides actuator isolation that allows the use of large-stroke single-axis actuators, and enables a complementary end-point sensing scheme that employs commonly available sensors. These attributes help achieve an unprecedented 10 mm × 10 mm motion range in the proposed nanopositioning system. Having overcome the physical system design challenges, a dynamic model of proposed nanopositioning system is created and verified via system identification methods. In particular, dynamic non-linearities associated with the large displacements of the flexure mechanism and resulting controls challenges are identified. The physical system is fabricated, assembled, and tested to validate its simultaneous large range and nanometric motion capabilities. Preliminary closed-loop test results, which highlight the potential of this new design configuration, are presented.Copyright © 2010 by ASME

Hydrogel sensors and actuators

Abstract: General Properties of Hydrogels.- Synthesis of Hydrogels.- Swelling-Related Processes in Hydrogels.- Modelling and Simulation of the Chemo-Electro-Mechanical Behaviour.- Hydrogels for Chemical Sensors.- Hydrogels for Biosensors.- Hydrogels for Actuators.- Polymer Hydrogels to Enable New Medical Therapies.

Large deformation and electromechanical instability of a dielectric elastomer tube actuator

Abstract: This paper theoretically analyzes a dielectric elastomer tube actuator (DETA). Subject to a voltage difference between the inner and outer surfaces, the actuator reduces in thickness and expands in length, so that the same voltage will induce an even higher electric field. This positive feedback may cause the actuator to thin down drastically, resulting in electrical breakdown. We obtain an analytical solution of the actuator undergoing finite deformation when the elastomer obeys the neo-Hookean model. The critical strain of actuation is calculated in terms of various parameters of design. We also discuss the effect of the strain-stiffening on electromechanical behavior of DETAs by using the model of freely joined links.

Team Consensus for a Network of Unmanned Vehicles in Presence of Actuator Faults

Abstract: In this paper, performance analysis of a team of unmanned vehicles (agents) that are subject to actuator faults is investigated. The team goal is to accomplish a cohesive motion in a modified leader-follower architecture by using a semi-decentralized optimal control strategy. The controller, which is recently proposed by the authors, is designed based on minimization of individual cost functions by using the available information from the neighboring sets. It is shown that a loss of effectiveness (LOE) fault in an actuator does not deteriorate the stability nor the consensus seeking goal of the team. This fault would only result in a different transient behavior, e.g., a change in the agent's convergence rate, without a change in the consensus value. On the other hand, if the fault in one or more of the agents is of the float type, either in the leader or the followers, the team could not maintain its consensus any longer, however the stability of the team can still be guaranteed. Moreover, the leader and the healthy followers adapt themselves to the follower's change when a float fault occurs in one of the agents. Finally, the behavior of the team in presence of the lock-in-place (LIP) actuator fault is also investigated. Simulation results are provided to demonstrate the performance of the team subject to the above three actuator fault scenarios.

Tracking control of pneumatic artificial muscle actuators based on sliding mode and non-linear disturbance observer

Abstract: The dynamic properties and non-linear control of the pneumatic muscle actuator (PMA) were investigated in this study for use in a specially designed hand rehabilitation device. The phenomenological model of PMA was established in the lower pressure range applicable for hand rehabilitation. The experimental results show that PMA's characteristics can be approximated by piecewise functions. In order to improve the performance and robustness of control for accurate trajectory tracking, a sliding mode control based on non-linear disturbance observer (SMCBNDO) was designed. The simulation and experimental results demonstrated that the model and the sliding mode control achieved the desired performance in tracking a desired trajectory within guaranteed accuracy. The work indicates that the model and the non-linear control proposed in this study can be applied in PMA-driven hand function rehabilitation devices requiring lower pressures.

Disk drive employing comb filter for repeatable fly height compensation

Abstract: A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of tracks. The disk drive further comprises a fly height actuator operable to adjust a fly height of the head. A fly height measurement (FHM) is generated for the head, and a fly height error (FHE) is generated as a difference between the FHM and a target fly height. A comb filter is used to generate fly height compensation values in response to the FHE, and a fly height control signal is generated in response to the FHE and the fly height compensation values, wherein the fly height control signal is applied to the fly height actuator.