Showing papers on "Actuator published in 2002"

Apparatus and method for performing surgery on a patient

Abstract: The invention provides an apparatus and method for performing surgery on a patient. The surgical apparatus includes an input device, at least one hydraulic amplifier operably attached to the input device, and an actuator operably attached to the hydraulic amplifier. Input to the input device is hydraulically modulated via the hydraulic amplifier to manipulate the actuator. The surgical method includes receiving a mechanical input for an action. The mechanical input is hydraulically modulated. The action is controlled based on the hydraulically modulated input.

Haptic interface for laptop computers and other portable devices

Abstract: A haptic feedback touch control used to provide input to a computer. A touch input device includes a planar touch surface that provides position information to a computer based on a location of user contact. The computer can position a cursor in a displayed graphical environment based at least in part on the position information, or perform a different function. At least one actuator is also coupled to the touch input device and outputs a force to provide a haptic sensation to the user. The actuator can move the touchpad laterally, or a separate surface member can be actuated. A flat E-core actuator, piezoelectric actuator, or other types of actuators can be used to provide forces. The touch input device can include multiple different regions to control different computer functions.

Reliable robust flight tracking control: an LMI approach

Abstract: This paper studies the reliable robust tracking controller design problem against actuator faults and control surface impairment for aircraft. First, models of actuator faults and control surface impairment are presented. Then a reliable robust tracking controller design method is developed. This method is based on the mixed linear quadratic (LQ)//H/sub /spl infin// tracking performance index and multiobjective optimization in terms of linear matrix inequalities. Flight control examples are given, and both linear and nonlinear simulations are given.

Device provided with magnetic position sensor

Abstract: (57) [Problem] To provide an apparatus having a magnetic position sensor. The present invention relates to an actuator having a magnetic field sensor (5), a rod-shaped component (3), particularly an element (M) for generating a magnetic field (4), and a position sensor for measuring a magnetic field strength angle of the magnetic field. For a device having a magnetic position sensor with analytical electronics (7) for linear displacement of the axis of the axis, the electric field angle signal determined by this sensor is used for the displacement path determination. The element generating the magnetic field (4) is an axially magnetized magnet casing (M) surrounding the rod-shaped component (3) of the actuator itself, which is fixedly connected to it and its displacement axis (z ) Can rotate with it.

High bandwidth nano-positioner: A robust control approach

Abstract: This article presents the design, identification, and control of a nano-positioning device suited to image biological samples as part of an atomic force microscope. The device is actuated by a piezoelectric stack and its motion is sensed by a linear variable differential transformer. It is demonstrated that the conventional proportional-integral control architecture does not meet the bandwidth requirements for positioning. The design and implementation of an H∞ controller demonstrates substantial improvements in the positioning speed and precision, while eliminating the undesirable nonlinear effects of the actuator. The characterization of the resulting device in terms of bandwidth, resolution, and repeatability provided illustrates the effectiveness of the modern robust control paradigm.

Fast and Robust

Abstract: Robots to date lack the robustness and performance of even the simplest animals when operating in unstructured environments. This observation has prompted an interest in biomimetic robots that take design inspiration from biology. However, even biomimetic designs are compromised by the complexity and fragility that result from using traditional engineering materials and manufacturing methods. We argue that biomimetic design must be combined with structures that mimic the way biological structures are composed, with embedded actuators and sensors and spatially-varied materials. This proposition is made possible by a layered-manufacturing technology called shape deposition manufacturing SDM. We present a family of hexapedal robots whose functional biomimetic design is made possible by SDM's unique capabilities and whose fast over four body-lengths per second and robust traversal over hip-height obstacles performance begins to compare to that seen in nature. We describe the design and fabrication of the robots and we present the results of experiments that focus on their performance and locomotion dynamics.

Series elastic actuators for high fidelity force control

Abstract: 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.

Wind turbine blade

Abstract: The invention relates to a wind turbine blade with at least one control surface and an actuator inside the main body of the wind turbine blade for moving the control surface, wherein the actuator comprises a fluidic muscle, a controller and a pump, and wherein the fluidic muscle is adapted to change in length and width when the pressure of the fluid within the fluidic muscle is varied.

Limited Data Rate in Control Systems with Networks

Abstract: From the Publisher: This book incorporates data rate issues that arise in control design for systems involving communication networks The general setup is that, given a plant, a communication channel with limited data rate and control objectives, one must find a controller that uses the channel in the feedback loop to achieve the control objectives The theoretical question of interest is to find the minimum data rate necessary for the channel This book is motivated by the recent developments in communication technology and aims at engineers and scientists in this field The use of networks has become common practice in many control applications connecting sensors/actuators to controllers The book therefore provides the fundamentals of the networks used in control systems, based on hybrid systems theory The book focuses on the use of networks in distributed systems and on quantization in messages sent over networks

An adaptive actuator failure compensation controller using output feedback

Abstract: An adaptive control scheme using output feedback for output tracking is developed for systems with unknown actuator failures. Such actuator failures are characterized by some unknown inputs stuck at some unknown fixed values at unknown time instants. An effective output feedback controller structure is proposed for actuator failure compensation. When implemented with true matching parameters, the controller achieves desired plant-model output matching. When implemented with adaptive parameter estimates, the controller achieves asymptotic output tracking. A stable adaptive law is derived for parameter adaptation in the presence of parameter uncertainties. Closed-loop signal boundedness and asymptotic output tracking, despite the uncertainties in actuator failures and plant parameters, are ensured analytically and verified by simulation results.

Stabilizing a linear system by switching control with dwell time

Abstract: The use of networks in control systems to connect controllers and sensors/actuators has become common practice in many applications. This new technology has also posed a theoretical control problem of how to use the limited data rate of the network effectively. In this paper, we consider a system where its sensor and actuator are connected by a finite data rate channel. A design method to stabilize a continuous-time, linear plant using a switching controller is proposed. In particular, to prevent the actuator from fast switching, or chattering, which can not only increase the necessary data rate but also damage the system, we employ a dwell-time switching scheme. It is shown that a systematic partition of the state-space enables us to reduce the complexity of the design problem.

An antiwindup approach to enlarging domain of attraction for linear systems subject to actuator saturation

Abstract: The article considers linear systems subject to actuator saturation. An antiwindup technique is used to enlarge the domain of attraction of the closed-loop system under an a priori designed linear dynamic feedback law. The design of the antiwindup compensation gain is formulated and solved as an iterative optimization problem with LMI constraints. Numerical examples are used to demonstrate the effectiveness of the proposed design technique.

Investigation of wall normal electromagnetic actuator for seawater flow control

Abstract: Electromagnetic (EM) flow control deals with the concept of using in combination ‘wall-flush’ electrodes ( j , dc current supply) and ‘sub-surface’ magnets ( B , magnetic induction origin) to create directly local body forces ( j × B ) within a seawater boundary layer. Analytical, experimental and computational investigations of EM flow control are presented here. This work is intended to provide understanding of the basic mechanisms involved in turbulence intensity and skin friction reductions as well as in coherent structure extinction. First, the EM actuator and its modes of action are described. This description includes some general remarks on the EM actuator, the set of equations suitable for EM control in seawater and a selection of dimensionless parameters analysed in terms of possible mechanisms of action. Second, some experimental investigations and visualizations of wall-bounded flows under EM actuation are presented: the near-wall vortex around the actuator; the suction zone above the actuat...

Tailless aircraft flight control using multiple time scale reconfigurable sliding modes

Abstract: A triple time scale tailless aircraft flight control problem is addressed via continuous sliding mode control. A reconfigurable sliding mode flight controller is designed that achieves robust, high accuracy command angle tracking both before and after damage to an aircraft. Command angles and angular rate commands are robustly tracked in outer and inner loops correspondingly via finite reaching time continuous sliding mode controllers. An optimal control allocation algorithm is employed using nominal mathematical model of an aircraft. Sliding surface boundary layer reconfiguration (direct adaptation) is used in the "very" inner loop to account for actuator dynamics, deflection limits, and rate limits. Online damage identification is not required by this design. The reconfigurable sliding mode flight control technique is applied to a flight dynamics model of a tailless jet fighter that was developed under is the innovative control effectors program. Simulations demonstrate stability and high accuracy tracking performance without violation of actuator limits.

Strain Response from Polypyrrole Actuators under Load

Abstract: The strain generated by an actuator material when subjected to an external force is a key performance parameter. However, very little is known about the performance of polymer actuator materials when subjected to external loads. Increasing external loads were applied to polypyrrole films and the actuator response was found to decrease linearly. Analysis of the effects of the applied load on actuator strain showed that the rate of strain decrease with increasing load depended upon the difference in the Young’s modulus of the polymer in the doped and undoped states. A simple analytical model shows good agreement with the experimental data.

Magnetic position sensor for measuring linear displacement

Abstract: The invention relates to a device with a magnetic position sensor comprising a field sensor ( 5 ) and analysis electronics ( 7 ) for linear displacements of a rod-shaped component ( 3 ), in particular the shaft of an actuator, with an element (M) generating a magnetic field ( 4 ) and a position sensor measuring the magnetic field strength angle of this field, the field angle signal determined by this sensor being used for displacement path determination. The element generating a magnetic field ( 4 ) is an axially magnetized magnet casing (M) which surrounds the rod-shaped component ( 3 ) of the actuator itself, is fixedly connected thereto and can rotate therewith about its displacement axis (z).

Stability and Delay Compensation for Real-Time Substructure Testing

Abstract: Real-time substructure testing is a method for establishing the dynamic behavior of structural systems. The method separates a complex structure into physical and numerically modeled substructures, which interact in real-time allowing time-dependent nonlinear behavior of the physical specimen to be accurately represented. Displacements are applied to the physical specimen using hydraulic actuators and the resulting measured forces are fed back to the numerical substructure. This feedback loop is implemented as a time-stepping routine. One of the key factors in obtaining reliable results using this method is the accurate compensation of the delayed response of the actuator. If this is not accounted for, instability of the feedback loop is likely to occur. This paper presents a method for estimating the delay while a test is in progress and accurately compensating for it during the test. The stability of both linear and nonlinear single-actuator systems is examined and the behavior of twin-actuator systems ...

Microneedle transport device

Abstract: A transdermal transport device (10) includes a reservoir (46) for holding a formulation of an active principle, and an array of needles (12) which have bores in fluid communication with the reservoir to facilitate transporting the formulation to and from the reservoir through the needles. The device also includes a first actuator (24) which drives the array of needles into the body, and a second actuator (38) which pumps the formulation between the reservoir and the body through the needles. The first actuator is reversible to withdraw the needles from the body.

Electromechanical modeling and characterization of ionic polymer benders

Abstract: This paper presents a coupled, electromechanical model of a Nafion-based ionic polymer transducer used in the cantilevered bender configuration. A comparison of simulatedandexperimental responses for a 0.2 mm 5.0 mm 17 mm actuator validates both the form of the model and the empirically determined model parameters. In one of the experiments used for parameter identification, the short circuit current is found to be proportional to the induced actuator velocity, with the constant of proportionality on the order of 104A/(m/s). This dynamic model differs from those presented by other researchers in that it is able to represent the transducer as either a sensor or as an actuator. Also presented is an assessment of the polymer actuators’ ability to perform mechanical work. The results of a series of force versus deflection experiments are outlined, and energy densities are calculated to facilitate comparison with other actuator technologies. The maximum blockedforce with a 1.25 V step input was 1.6 mN (with a ...

Basic properties of magnetic shape memory actuators

Abstract: Magnetically controlled shape memory materials are a new w ay to p roduce motion and force. The material changes s hape in a magnetic field. Shape c hanges are e ven l0 p ercent and response time is less than a millisecond. Usual applications of the material are ac tuators that produce linear motion. In this article several magnetic shape memory actuators are presented and their properties and advantages are discussed.

Current drive methods to extend the range of travel of electrostatic microactuators beyond the voltage pull-in point

Abstract: When a voltage source drives an electrostatic parallel plate actuator, the well-known pull-in instability limits the range of displacement to 1/3 of the gap. Different strategies have been reported to overcome this limitation. More recently, experimental results have been presented using a capacitor in series with the actuator. Nevertheless, this strategy requires higher voltage than the pull-in voltage value to achieve full range of travel. In order to reduce the operating voltage, a switched-capacitor configuration has been also proposed. In this paper, two different approaches are introduced to control charge in the actuator by means of current driving. Theoretical equations derived for each method show that full range of travel can be achieved without voltage penalty. Both approaches are based on the use of current pulses injecting the required amount of charge to fix the position of the movable plate. Experimental measurements, showing that displacement beyond the pull-in point can be achieved, are in good agreement with the theoretical and the predicted simulated behavior.

Actuator Classification and Selection—The Development of a Database

Abstract: Actuators are controllable work-producing devices. A strategy for selecting actuators to meet specified design requirements is described here. A number of considerations enter: the type and characteristics of the actuator, the nature of the power-source (the fuel) that is required to drive it, and the possible need of an interface between the two to convert the energy into a form that the actuator can accept. The strategy is demonstrated by software that includes a database for some 220 actuators drawn from 18 families, and an advanced selection engine. Case studies are used to illustrate its use.

Modeling and control of a magnetostrictive actuator

Abstract: The rate-dependent hysteresis existing in magnetostrictive actuators presents a challenge in control of these actuators. In this paper we propose a novel dynamical model for the hysteresis in a thin magnetostrictive actuator. The model features the coupling of the Preisach operator with an ordinary differential equation (ODE). We prove the well-posedness of the model, study the parameter identification methods, and propose an inverse control scheme. The effectiveness of the identification and inverse control schemes is demonstrated through experimental results.

Characterization and optimization of scan speed for tapping-mode atomic force microscopy

Abstract: Increasing the imaging speed of tapping mode atomic force microscopy (AFM) has important practical and scientific applications. The scan speed of tapping-mode AFMs is limited by the speed of the feedback loop that maintains a constant tapping amplitude. This article seeks to illuminate these limits to scanning speed. The limits to the feedback loop are: (1) slow transient response of probe; (2) instability limitations of high-quality factor (Q) systems; (3) feedback actuator bandwidth; (4) error signal saturation; and the (5) rms-to-dc converter. The article will also suggest solutions to mitigate these limitations. These limitations can be addressed through integrating a faster feedback actuator as well as active control of the dynamics of the cantilever.

Electronic lock control and sensor module for a wireless system

Abstract: A lock system includes a cylindrical door lock having a latching spindle and an opening spindle which are concentrically oriented, and a wireless communication system to transmit signals indicating the relative positions of the latching spindle and the opening spindle. A door lock assembly can include a lock mechanism for placing the lock assembly into an unlocked state or a locked state, an electrically controlled actuator assembly to control the lock mechanism, a transceiver coupled to the actuator assembly, and a communication device to communicate over a two-way wireless network with the electrically controlled actuator. A retrofit actuator assembly adapted to be mounted on an existing lock to control a locking mechanism of the lock, and a two-way communication device to control the retrofit actuator assembly and to receive signals from the retrofit actuator assembly indicating a state of the locking mechanism.

Active vibroacoustic control with multiple local feedback loops.

Abstract: When multiple actuators and sensors are used to control the vibration of a panel, or its sound radiation, they are usually positioned so that they couple into specific modes and are all connected together with a centralized control system. This paper investigates the physical effects of having a regular array of actuator and sensor pairs that are connected only by local feedback loops. An array of 4×4 force actuators and velocity sensors is first simulated, for which such a decentralized controller can be shown to be unconditionally stable. Significant reductions in both the kinetic energy of the panel and in its radiated sound power can be obtained for an optimal value of feedback gain, although higher values of feedback gain can induce extra resonances in the system and degrade the performance. A more practical transducer pair, consisting of a piezoelectric actuator and velocity sensor, is also investigated and the simulations suggest that a decentralized controller with this arrangement is also stable over a wide range of feedback gains. The resulting reductions in kinetic energy and sound power are not as great as with the force actuators, due to the extra resonances being more prominent and at lower frequencies, but are still worthwhile. This suggests that an array of independent modular systems, each of which included an actuator, a sensor, and a local feedback control loop, could be a simple and robust method of controlling broadband sound transmission when integrated into a panel.

Heat transfer analysis and optimization of two-beam microelectromechanical thermal actuators

Abstract: This article investigates rectangular two-beam microelectromechanical thermal actuators and provides a method for their optimization. The thermal actuators investigated consisted of two asymmetric parallel arms,one thin and one wide. Under an electric current load, the thin arm heats and expands more than the wide arm, thereby bending the entire structure. Simplified models of the heat transfer mechanisms are used to determine the temperature profile. From the thermal expressions for expansion of the arms, equations are derived to predict the deflection as well as the buckling loads. Measurements of the actuator deflection as a function of voltage are presented. Design guidelines are introduced for optimization of a thermal actuator.

Robust stabilization of nonlinear uncertain plants with backlash or dead zone in the actuator

Abstract: Actuator nonlinearities are often neglected in control system design, though they can remarkably affect systems performance. This paper presents sliding mode controllers able to robustly stabilize an intrinsically nonlinear uncertain plant, in the presence of dead zone or backlash in the actuator devices. These nonlinearities have been assumed uncertain, too, with known bounds on the parameters. In the case of backlash, two different approaches have been presented, obtained using a "quasistatic" and a "dynamic" description of the nonlinearity. Simulation results for a single input-single output (SISO) plant have been provided, addressing both the stabilization and the servo problem for a mechanical system representing a robot-like system with one link.