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smart structures and materials 1994: Passive Damping

作者： Schmitz, E. Richards, K.E. Voth, C.T. Martin Marietta Astronautics Group P.O. Box 179 DenverCO80201-0179 United States

A general design methodology to integrate active control with passive damping has been demonstrated on the NASA LaRC CSI Evolutionary Model (CEM), a ground testbed for future large, flexible spacecraft. A limited bandwidth active controller is designed with a frequency-shaped H2 algorithm which minimizes the response of a Line-of-Sight (LOS) measurement system. Using the Modal Strain Energy (MSE) method, a passive damping treatment is designed based on damping level requirements for a set of targeted modes in the high-frequency band, beyond the active control bandwidth. The damping levels are selected to achieve robustness as well as the same level of performance in the high frequency band as in the active control band with. A set of 60 viscoelastic damped struts were designed and fabricated for the CEM. Identified damping levels from 3% to 5% were achieved for the dominant targeted modes;about twice the targeted levels and an order of magnitude larger than for the untreated structure. Using measured impedance data for the individual damped struts, analytical predictions of the damping levels were very close to the experimental values in the frequency range where the undamped open-loop model matched the experimental data. An integrated active/passive controller was successfully implemented on the CEM and was evaluated against an active-only controller. A two-fold increase in the effective control bandwidth and further reductions of 30% to 50% in the LOS root mean-square (RMS) outputs were achieved compared to an active-only controller. © 1994 SPIE. All rights reserved.

关键词： controllers

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Collocated independent modal control with self-sensing orthogonal piezoelectric actuators (theory and experiment)

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smart materials and structures 1994年第3期3卷 277-284页

作者： Tzou, H.S. Hollkamp, J.J. Department of Mechanical Engineering University of Kentucky Lexington KY 40506-0046 United States Wright Laboratory Flight Dynamics Directorate WL/FIBG Dayton OH 45433 United States

Distributed self-sensing piezoelectric actuators provide perfect collocations of sensors and actuators in closed-loop structural controls. To achieve independent control of various natural modes, spatially distributed self-sensing orthogonal piezoelectric actuators are proposed in this study. A generic spatially shaped orthogonal sensor/actuator theory is derived first, followed by an application to a Bernoulii-Euler beam. Spatially distributed orthogonal sensors/actuators are designed based on the modal strain functions and they are fabricated using a 40 μm piezoelectric polymer. A cantilever beam laminated with these self-sensing orthogonal piezoelectric actuators combined with a self-sensing feedback control circuit is tested. Collocated independent modal control of the cantilever beam with spatially distributed self-sensing orthogonal actuators is demonstrated and control effectiveness studied. © 1994 IOP Publishing Ltd.

关键词： Piezoelectric actuators

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Bending-vibration control of composite and isotropic plates through intelligent constrained-layer treatments

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smart materials and structures 1994年第1期3卷 59-70页

作者： Shen, I.Y. Univ of Washington Seattle United States

In this paper intelligent constrained-layer (ICL) damping treatments are applied to control bending vibration of composite and isotropic plates. The ICL damping treatment consists of a viscoelastic shear layer sandwiched between a piezoelectric constraining cover sheet and the structure to be damped. According to the measured vibration response of the structure, the feedback controller regulates axial deformation of the piezoelectric layer to perform active vibration control. The equation of motion and boundary conditions governing the bending vibration of a composite plate processing bending-stretching coupling stiffness with ICL damping treatments are derived. Two examples are illustrated in this paper. The first example considers an infinite composite plate consisting of a ±45° angle ply laminate subjected to plane harmonic wave excitations. An ICL treatment with an idealized, distributed sensor and a proportional-plus-derivative feedback controller is used to control the bending vibration of the composite plate. Compared with existing passive constrained layer treatments, numerical results show that the ICL damping treatment can produce significant damping. In addition, there are certain orientations, determined by the structures of the composite laminate, along with the vibration amplitude can be reduced to a minimum. The second example considers bending-vibration control of a simply supported rectangular, isotropic classical plate through use of ICL treatment. The equation of motion is first obtained from that of the composite plate with the bending stiffness matrix, the extensional stiffness matrix, and the bending-extension coupling stiffness matrix replaced by isotropic elastic constants. A four-mode Galerkin approximation shows that the vibration amplitude of the first bending-vibration mode can be reduced significantly through ICL. The second bending-vibration mode, though uncontrollable for a simply-supported rectangular plate, will have finite amplitude

关键词： Composite structures

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Active control of far-field sound radiation by a beam with piezoelectric control transducers: Physical system analysis

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smart materials and structures 1994年第4期3卷 476-484页

作者： Wang, Bor-Tsuen Department of Mechanical Engineering National Pingtung Polytechnic Institute Pingtung 91207 Taiwan

This paper analytically demonstrates the use of piezoelectric actuators and PVDF sensors to actively control the far-field sound radiation from a simply-supported beam in an infinite rigid baffle. The beam is assumed to be subjected to a harmonic point force. The piezoelectric patches which are attached to the beam serve as actuators to control the sound radiated from the beam into the far-field, while the PVDF films serve as structural error sensors. A minimization process is used to calculate the optimal input voltages into the piezoelectric actuators so as to minimize the cost function which is the least mean square value of the error sensor signals. Radiation directivity patterns are plotted, and the wavenumber analysis is performed to evaluate the control effectiveness. Results show that the use of the compact distributed types of actuators and sensors can efficiently attenuate the far-field sound radiation. The reduction of sound pressure level for on-resonance cases is over 20-50 dB;however, little attenuation can be achieved or even spillover may occur for off-resonance cases due to the arbitrary location of actuators and sensors. This work demonstrates the use of structural actuators and near-field sensors for far-field sound radiation control and leads to the inherent application of an intelligent material structure system. © 1994 IOP Publishing Ltd.

关键词： Piezoelectric actuators

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BOUNDARY DIFFUSION-controlLED CREEP MODEL IN NANOCRYSTALS

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AIAA JOURNAL 1994年第2期32卷 436-438页

作者： KANIARIS, KP LYRINTZIS, CS SAN DIEGO STATE UNIV DEPT AEROSP ENGN & ENGN MECHSAN DIEGOCA 92182

Nanocrystalline materials (NCMs) by definition are single or multiphase polycrystals with a crystal size on the order of 1-10nm. NCMs seem to permit the alloying of components, which results in alloys with properties attractive to the aerospace industry. The research around nanocrystals adds a few more difficulties. There is a smaller size and very random arrangement of atoms. Such uncontrollable characteristics are related to the viscosity model by Herring. The focus of this paper is to improve the creep model accepted today along with its diffusivity parameters. By using both the Coble and Herring models and Coffey's assumptions for grain boundary sources and by adjusting the vacancy concentration gradient one can derive a more accurate nanocrystalline creep equation.

关键词： Creep Nanocrystals smart materials and structures Harmonic Oscillator Stress Distribution Cantilever Beam Vortices Diffusion Coefficient Active Vibration control Distributed Parameter System

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The application of multi-channel design methods for vibration control of an active structure

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smart materials and structures 1994年第3期3卷 329-343页

作者： Prakah-Asante, Kwaku O. Craig, Kevin C. Department of Mechanical Engineering Aeronautical Engineering and Mechanics Rensselaer Polytechnic Institute Troy NY 12180 United States

In conjunction with appropriate control architecture techniques, an active structure is typically designed to modify its dynamic response to reduce vibration by changing its dynamic properties, such as damping and stiffness, and its disturbance rejection characteristics. To obtain effective vibration minimization, it is advantageous to cancel vibrations at multiple locations on the structure. This paper presents multi-channel control methods for actively controlling vibration transmission of disturbances in a typical finite beam structure bonded with piezoelectric sensors and actuators. The control architecture is geared towards disturbance rejection and enhanced performance, while maintaining robustness to the active structure plant variations and modeling uncertainties. The methods investigated include linear/non-linear rate feedback control, linear quadratic Gaussian/loop transfer recovery control with augmented states to obtain disturbance accommodation, H∞ optimization control, and adaptive feedforward multi-channel control based on the least-mean-squares algorithm. The effectivenes of the control schemes is evaluated and the advantages and disadvantages in their application are discussed. A hybrid multi-channel control formulation is developed to account for both steady state and transient vibrations. Numerical and experimental results from the application of the control strategies to obtain vibration minimization are presented. © 1994 IOP Publishing Ltd.

关键词： Disturbance rejection

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Active beam vibration control using PZT actuators

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Integrated Ferroelectrics 1994年第3 PT 2期4卷 281-291页

作者： Wu, S.Y. Tran, B.N. Davis, F.Y. Trent, C.L. Edberg, D.L. Geideman, W.A. McDonnell Douglas Aerospace Huntington Beach United States

smart materials of lead-zirconate-titanate (PZT) piezoelectric ceramics have attracted attention in recent years for active vibration control, acoustic noise suppression, health monitoring and damage assessment. We at McDonnell Douglas Aerospace have been studying these ceramics for use as sensors and actuators in various space and aircraft structures. In this paper, we will report results of a recent study on active vibration control using monomorph PZT actuators. The experiments were performed on thin aluminum cantilever beams. Collocated and non-collocated sensors and actuators were employed. Two control techniques: the classical velocity feedback and adaptive feedback controls, were investigated. We have obtained significant damping and broadband vibration attenuation of greater than 30 dB using the classical control with the single-input single-output feedback approach. A 24 dB reduction has also been achieved using the adaptive control with the multiple-input single-output approach. Detailed experimental methods and results will be described.

关键词： Actuators

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218 smart structures and materials systems

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control Engineering Practice 1994年第3期2卷 542-542页

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Modeling and robust control of smart structures

Modeling and robust control of smart structures

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smart structures and materials 1993: mathematics in smart structures

作者： Tebbe, Chris D. Schroeder, Tim G. Butler, Robert K. Rao, Vittal S. Koval, Leslie R. et.al. Univ. of Missouri/Rolla Rolla MO USA

ISBN: (纸本)0819411523

The design and implementation of control strategies for large, flexible smart structures presents challenging problems. One of the difficulties arises in the approximation of high-order finite element models with low order models. Another difficulty in controller design arises from the presence of unmodeled dynamics and incorrect knowledge of the structural parameters. In this paper, the balance-truncation reduced-order models are employed in deriving lower-order models for complex smart structures. These methods do not introduce any spill-over problems in the closed-loop response of the system. The simplified analytical models are compared with models developed by structural identification techniques based on vibration test data. To minimize the effects of uncertainties on the closed-loop system performance of smart structures, robust control methodologies have been employed in the design of controllers. The reduced order models are employed in the design of robust controllers. To demonstrate the capabilities of shape-memory-alloy actuators, we have designed and fabricated a three-mass test article with multiple shape-memory-alloy (NiTiNOL) actuators. Generally, the non-collocation of actuators and sensors presents difficulties in the design of controllers. controllers for a test article with non-collocated sensors and actuators are designed, implemented and tests. The closed-loop system response of the test article with two actuators and sensors has been experimentally determined and presented in the paper.

关键词： Shape memory effect

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APPLICATION OF DESIGN OPTIMIZATION TECHNIQUES FOR VIBRATION control OF structures USING PIEZOELECTRIC DEVICES

APPLICATION OF DESIGN OPTIMIZATION TECHNIQUES FOR VIBRATION ...

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1993 smart structures AND materials CONF : smart structures AND INTELLIGENT SYSTEMS

作者： CHATTOPADHYAY, A SEELEY, CE Arizona State Univ. (United States)

ISBN: (纸本)0819411507

Active vibration control of structures using piezoelectric materials is a new approach for damping unwanted vibrations in structures lacking sufficient stiffness or passive damping. The finite elements method is used to model active damping elements which are piezoelectric actuators bonded to a box beam. Efficient implementation of these actuators requires that their optimal locations on the structure be determined and that the structure be designed to best utilize the properties of the piezoelectrics. A formal optimization procedure has been developed to address both of these issues. Multiobjective optimization techniques are used to minimize multiple and conflicting design objectives such as mass and energy dissipated by the piezoelectric actuators.

关键词： Actuators Intelligence systems smart structures Structural design Vibration control control systems Finite element methods Ferroelectric materials Optimization (mathematics) Sensors

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