Piezo-actuated stages have become more and more promising in nanopositioning applications due to the excellent advantages of the fast response time, large mechanical force, and extremely fine resolution. Modeling and control are critical to achieve objectives for high-precision motion. However, piezo-actuated stages themselves suffer from the inherent drawbacks produced by the inherent creep and hysteresis nonlinearities and vibration caused by the lightly damped resonant dynamics, which make modeling and control of such systems challenging. To address these challenges, various techniques have been reported in the literature. This paper surveys and discusses the progresses of different modeling and control approaches for piezo-actuated nanopositioning stages and highlights new opportunities for the extended studies.

Modeling and Control of Piezo-Actuated Nanopositioning Stages: A Survey

This book is a companion text to Active Control of Sound by P.A. Nelson and S.J. Elliott, also published by Academic Press. It summarizes the principles underlying active vibration control and its practical applications by combining material from vibrations, mechanics, signal processing, acoustics, and control theory. The emphasis of the book is on the active control of waves in structures, the active isolation of vibrations, the use of distributed strain actuators and sensors, and the active control of structurally radiated sound. The feedforward control of deterministic disturbances, the active control of structural waves and the active isolation of vibrations are covered in detail, as well as the more conventional work on modal feedback. The principles of the transducers used as actuateors and sensors for such control strategies are also given an in-depth description. The reader will find particularly interesting the two chapters on the active control of sound radiation from structures: active structural acoustic control. The reason for controlling high frequency vibration is often to prevent sound radiation, and the principles and practical application of such techniques are presented here for both plates and cylinders. The volume is written in textbook style and is aimed at students, practicing engineers, and researchers.

Active control of vibration, 1st edition

In this paper we review essential aspects in- volved in the design of an active vibration control system. We present a generic procedure to the design process and give selective examples from the literature on relevant ma- terial. Together with examples of their applications, various topics are briefly introduced, such as structure modeling, model reduction, feedback control, feedforward control, con- trollability and observability, spillover, eigenstructure assign- ment (pole placement), coordinate coupling control, robust control, optimal control, state observers (estimators), intelli- gent structure and controller, adaptive control, active con- trol effects on the system, time delay, actuator-structure interaction, and optimal placement of actuators.

Active Structural Vibration Control: A Review

Over the last few decades, extensive use of flexible manipulators in various robotic applications has made it as one of the research interests for many scholars over the world. Recent studies on the modeling, sensor systems and controllers for the applications of flexible robotic manipulators are reviewed in order to complement the previous literature surveyed by Benosman & Vey (Robotica 22:533---545, 2004) and Dwivedy & Eberhard (Mech. Mach. Theory 41:749---777, 2006) . A brief introduction of the essential modeling techniques is first presented, followed by a review of the practical alternatives of sensor systems that can help scientists or engineers to choose the appropriate sensors for their applications. It followed by the main goal of this paper with a comprehensive review of the control strategies for the flexible manipulators and flexible joints that were studied in recent literatures. The issues for controlling flexible manipulators are highlighted. Most of the noteworthy control techniques that were not covered in the recent surveys in references (Benosman & Vey Robotica 22:533---545, 2004; Dwivedy & Eberhard Mech. Mach. Theory 41:749---777, 2006) are then reviewed. It concludes by providing some possible issues for future research works.

Review of Control and Sensor System of Flexible Manipulator

We describe and report first results from PALM-3000, the second-generation astronomical adaptive optics (AO) facility for the 5.1 m Hale telescope at Palomar Observatory. PALM-3000 has been engineered for high-contrast imaging and emission spectroscopy of brown dwarfs and large planetary mass bodies at near-infrared wavelengths around bright stars, but also supports general natural guide star use to V ≈ 17. Using its unique 66 × 66 actuator deformable mirror, PALM-3000 has thus far demonstrated residual wavefront errors of 141 nm rms under ~1'' seeing conditions. PALM-3000 can provide phase conjugation correction over a 6."4 × 6."4 working region at λ = 2.2 μm, or full electric field (amplitude and phase) correction over approximately one-half of this field. With optimized back-end instrumentation, PALM-3000 is designed to enable 10^(–7) contrast at 1" angular separation, including post-observation speckle suppression processing. While continued optimization of the AO system is ongoing, we have already successfully commissioned five back-end instruments and begun a major exoplanet characterization survey, Project 1640.

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PALM-3000: EXOPLANET ADAPTIVE OPTICS FOR THE 5 m HALE TELESCOPE

A compact matrix formulation using the impedance and mobility approach for the analysis of structural-acoustic systems

This paper describes a theoretical and experimental investigation into an active four-mount vibration isolation system, in which electromagnetic actuators are installed in parallel with each of the four passive mounts placed between a three-dimensional piece of equipment and a vibrating base structure. Decentralized velocity feedback control is applied, where each actuator is operated independently by feeding back the corresponding equipment vibration velocity at the same location. Although one end of the actuator acts at the sensor position on the equipment, the system is not collocated because of the reactive force at the other end acting on the flexible base structure, whose dynamics may be strongly coupled with the mounted equipment. The investigation of this actuator installation and its practical implementation are the motivation of this research. Isolation of low-frequency vibration is considered where the equipment can be modeled as a rigid body and the mounts as lumped-parameter springs and dampers. A general theoretical formulation for analysing multiple-mount vibration isolation systems using the impedance method is presented and is used to investigate the control mechanisms involved. Experimental results show that up to 14 dB reduction in the kinetic energy of the equipment can be achieved in practice. If very high gains are used in the experiments, however, instability occurs at low frequencies due to phase shifts in the transducer conditioning electronics.

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Decentralized control for multichannel active vibration isolation

This paper describes an analytical and experimental investigation into the active control of harmonic sound transmission in a structural–acoustic coupled system. A rectangular enclosure is considered that has five acoustically rigid walls and a flexible plate on the remaining side through which a harmonic sound wave is transmitted into the enclosure. The control system is designed to globally reduce the sound field inside the enclosure, and the roles of structural and acoustic actuators are of particular interest. Three control configurations, classified by the type of actuators, are compared and discussed. They are: (i) use of a single point-force actuator, (ii) use of a single acoustic piston source, and (iii) simultaneous use of both a point-force actuator and an acoustic piston source. It is shown both analytically and experimentally that the point-force actuator is effective in controlling plate-dominated modes while the acoustic source is effective in controlling cavity-dominated modes. Since the transmitted sound field is governed by both plate- and cavity-dominated modes, the hybrid use of both types of actuators is shown to be a desirable configuration for the active control of sound transmission into a structural–acoustic coupled system.

Active control of harmonic sound transmission into an acoustic enclosure using both structural and acoustic actuators

In-head localization of sound images is a critical problem in headphone reproduction. The paper investigates the degree of externalization in terms of the distance of auditory images for various synthesis and reproduction cases. An effective binaural headphone system was constructed by way of binaural synthesis using head-related impulse responses and individual headphone equalization using Wiener filter theory. The headphone system designed had an average reproduction performance error of 2.4% for five subjects with a random noise input, and was used to perform some subjective tests with a set of virtual sources equally spaced and distanced from the center of each subject's head in the horizontal plane. The effects of individual and nonindividual binaural syntheses and those of equalized and nonequalized reproductions were separately investigated. In the tests, each subject was instructed to indicate the distance of auditory images. The results obtained demonstrate that individual equalization is important for externalization, and individual synthesis is important for consistent distance perception. Thus, a combined use of both individual equalization and individual synthesis resulted in externalized sound images of a consistent distance.

Sang-Myeong Kim

Papers

A compact matrix formulation using the impedance and mobility approach for the analysis of structural-acoustic systems

Decentralized control for multichannel active vibration isolation

Active control of harmonic sound transmission into an acoustic enclosure using both structural and acoustic actuators

On the externalization of virtual sound images in headphone reproduction: A Wiener filter approach

Dynamic analysis and optimal design of a passive and an active piezo-electrical dynamic vibration absorber