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作者： Chantalakhana, Chak University of Sheffield

学位级别：博士

In this thesis, the author presents a numerical and experimental study of the application of active constrained layer damping to a clamped-clamped plate. Piezoelectric actuators with modal controllers are used to improve the performance of vibration suppression from the passive constrained layer damping treatment. Surface damping treatments are often effective at suppressing higher frequency vibrations in thin-walled structures such as beams, plates and shells. However, the effective suppression of lower frequency modes usually requires the additional of an active vibration control scheme to augment the passive treatment. Advances in the technologies associated with so-called smart materials are dramatically reducing the cost, weight and complexity of active structural control and make it feasible to consider active schemes in an increasing number of applications. Specifically, a passive constrained layer damping treatment is enhanced with an active scheme employing a piezoceramic (PZT) patch as the actuator. Starting with an established finite element formulation it is shown how model updating and model reduction are required to produce a low-order state-space model which can be used as the basis for active control. The effectiveness of the formulation is then demonstrated in a numerical study. Finally, in the description of the experimental study it is shown how modes in the frequency range from 0 to 600 Hz are effectively suppressed: the two lowest modes (bending and torsional) through active control, the higher modes (around ten in number) by the passive constrained damping layer. The study'S original contribution lies in the experimental demonstration that given a sufficiently accurate model of the plate and passive constrained damping layer, together with a suitable active feedback control algorithm, spillover effects are not significant even when using a single sensor and single actuator. The experimental traces show, in some instances, minor effects due to s

关键词： Piezoelectric actuators Vibration suppression

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Adaptive structures and coupled multi-field problems

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Stahlbau 2000年第6期69卷 446-454页

作者： Grohmann, Boris A. Wallmersperger, Thomas Kröplin, Bernd Leiter Instituts Statik/Dynam. L. Stuttgart Germany

The present paper deals with adaptive structures from the perspective of coupled multi-field problems. First, the characteristic capabilities of adaptive structures in aerospace engineering are introduced. Subsequently, four basic mechanisms of adaptive structures applications are given, namely shape adaptation, counteraction, energy absorption and active control of the energy exchange with the environment. Furthermore, adaptive materials are presented and compared concerning potential application areas and limitations. Thereafter, stimulated polymer gels are discussed in consideration of their application as artificial muscles or actuators with large active strains. The corresponding electro-chemo-mechanical multi-field problem and a suitable coupling strategy for its numerical solution are presented. Finally, the application of active materials to the adaptive camber control of helicopter rotor blades is treated. Coupled numerical simulations of the aeroelastically unbalanced smart structure concept are conducted.

关键词： Intelligent structures

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Localized Effects of Piezopolymer Devices on the Dynamics of Inflatable Space-Based structures

Localized Effects of Piezopolymer Devices on the Dynamics of...

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作者： Robert Brett Williams Virginia Polytechnic Institute and State University

学位级别：硕士

Inflatable space-based devices have become popular over the past three decades, as they offer minimized launch-mass and launch-volume. Since some satellites have mirror sections over fifty feet in diameter and struts with lengths over ninety feet, inflation while in orbit has become a necessary procedure. Once inflated, these space structures are subject to two types of vibrations: those induced mechanically by guidance systems and space debris and those induced thermally from variable amounts of direct sunlight as they orbit about earth. controlling vibrations of spaced-based structures is critical to ensuring optimal performance. The focus of this research is derived from an Air Force program to develop and model an active control system using smart materials to suppress the vibrations of inflatable communication satellites. When small piezoceramic devices are attached to an aluminum or steel structure, the effects of the piezo on the dynamic properties of the host are typically ignored. However, the inflatable satellites of interest to this project are manufactured from Kapton, a thin, light polyimide film. Therefore, even a piezopolymer film actuator, such as PVDF, could greatly change the mass and stiffness values in the area under and around the patch, altering the dynamic behavior of the satellite. Thin-walled pressure vessel theory was employed to assess the state of stress at any location on an inflated torus. A flat, rectangular coupon was selected at a general point on the structure and modeled as a membrane. The equation of motion for this membrane with clamped edges was derived and a closed-form solution for the natural frequencies and mode shapes was presented. The Rayleigh-Ritz and finite element methods were then seen to numerically approximate the natural frequencies and mode shapes for the bare membrane with a high degree of accuracy. A passive PVDF patch was then attached to the base membrane and the equation of motion derived using an energy appr

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Dynamic responses of smart composites using a coupled thermo-peizoelectric-mechanical model

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AIAA JOURNAL 2000年第10期38卷 1939-1948页

作者： Zhou, X Chattopadhyay, A Gu, HZ Arizona State Univ Dept Mech & Aerosp Engn Tempe AZ 85287 USA

A completely coupled thermo-piezoelecltic-mechanical theory is developed to model the dynamic: response of composite plates with surface-bonded piezoelectric actuators. A higher-order laminate theory is used to describe the displacement fields of both composite laminate and piezoelectric actuator layers to accurately model the transverse shear deformation, which is significant in moderately thick constructions. A higher-order temperature field is used to accurately describe the temperature distribution through the thickness of composite plates. A finite element model is developed to implement the theory. Thermal and piezoelectric loads are considered. The results obtained using this coupled theory are compared with those obtained using an uncoupled theory. Numerical results indicate that the thermo-piezoelectric-mechanical coupling has significant effect on the dynamic response of composite plates. Furthermore, coupling also affects the control authority of piezoelectric actuators.

关键词： Structural Damping Piezoelectric Actuators Stiffness Matrices Piezoelectric materials Electric Potential Vibration Amplitude Permittivity Thermal Conductivity Transverse Shear Thickness Ratio

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control of beam resonance response by non-uniformly distributed wave resistance

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Shock and Vibration Digest 2000年第1期32卷 43-43页

作者： Kovinskaya, S. Amromin, E. Khozikov, V.

The feasibility of controlling beam resonance using a non-uniform distribution of mass-rigidity properties is explored for beams in longitudinal motion. Using a numerical analysis, the authors show that the variations in wave resistance from the nonuniformly distributed cross-sectional areas along the beam can change the eigenfrequencies of the beams significantly. The variations in wave resistance can be made by changing the thickness of the beam or employing smart materials and structures that can influence the rigidity distribution.

关键词： Beams and girders

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Miniature vibration isolation system (MVIS)

Miniature vibration isolation system (MVIS)

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IEEE Conference on Aerospace

作者： C. Brackett K. Denoyer J. Jacobs T. Davis Space Vehicle Directorate Air Force Research Laboratory Kirtland NM USA Satellite Systems Operation Honeywell Inc. Glendale AZ USA

In recent years, there has been a significant interest in, and move towards using highly sensitive, precision payloads on space vehicles. In order to perform tasks such as communicating at extremely high data rates between satellites using laser cross-links, or searching for new planets in distant solar systems using sparse aperture optical elements, a satellite bus and its payload must remain relatively motionless. The ability to hold a precision payload steady is complicated by disturbances from reaction wheels, control moment gyroscopes, solar array drives, stepper motors, and other devices. Because every satellite is essentially unique in its construction, isolating or damping unwanted vibrations usually requires a robust system over a wide bandwidth. The disadvantage of these systems is that they typically are not retrofittable and not tunable to changes in payload size or inertias. The technology of smart materials enables an unprecedented level of integration of sensors, actuators, and structures; this integration provides the opportunity for new structural designs that can adaptively influence their surrounding environment. The Air Force Research Laboratory along with its partner DARPA, have initiated a program to develop a Miniature Vibration Isolation System (MVIS) (patent pending) for space applications. The MVIS program is a systems-level demonstration of the application of advanced smart materials and structures technology that will enable programmable and retrofittable vibration control of spacecraft precision payloads. The current effort has been awarded to Honeywell Satellite Systems Operation. AFRL is providing in-house research and testing in support of the program as well. The MVIS program will culminate in a flight demonstration that shows the benefits of applying smart materials for vibration isolation in space and precision payload control.

关键词： Payloads Artificial satellites Isolation technology Space technology Aerospace materials Vibration control Space vehicles Ultraviolet sources Planets Solar system

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Localized Effects of Piezopolymer Devices on the Dynamics of Inflatable Space-Based structures

Localized Effects of Piezopolymer Devices on the Dynamics of...

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作者： Williams, Robert Brett Virginia Tech | University

Thin-walled pressure vessel theory was employed to assess the state of stress at any location on an inflated torus. A flat, rectangular coupon was selected at a general point on the structure and modeled as a membrane. The equation of motion for this membrane with clamped edges was derived and a closed-form solution for the natural frequencies and mode shapes was presented. The Rayleigh-Ritz and finite element methods were then seen to numerically approximate the natural frequencies and mode shapes for the bare membrane with a high degree of accuracy. A passive PVDF patch was then attached to the base membrane and the equation of motion deriv

关键词： layered membrane PVDF satellites inflatable patch Thesis

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Active structural acoustic control within the German Adaptronik project

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smart materials Bulletin 2000年第10期2000卷 5-13页

作者： Holger Hanselka Bernd Vogl Dirk Mayer Institut für Mechanik Lehrstuhl für Adaptronik Otto-von-Guericke-Universität Magdeburg Universitätsplatz 2 D-39106 Magdeburg Germany

In 1997 the German federal ministry for education and research (BMBF), within the framework of an idea competition for future-oriented key technologies and their industrial utilisation, called for project proposals from industries and research for so-called “Leitprojekts” (“guiding” projects). An independent group of experts selected a few project proposals from the many submitted, and proposed them to BMBF for promotion. One of these projects is the “BMBF-Leitprojekt Adaptronik”, which is introduced in this article. The Leitprojekt Adaptronik, which is conducted under the responsibility of the Deutsches Zentrum für Luft- und Raumfahrt eV (DLR) in Braunschweig, focuses on the structure-conforming integration of piezoelectric fibres and patches in structures for lightweight construction. It is aimed at active vibration and noise reduction, contour deformation and micropositioning in terms of adaptronics in various industrial applications. The project targets are prototype assemblies from the fields of the automotive industry, rail vehicles, mechanical engineering, medical engineering, and aerospace. One special part of the project is active structural acoustic control (ASAC).

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Strategies for smart control of large structures

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Proceedings of SPIE - The International Society for Optical Engineering 1999年 3667卷 604-613页

作者： Klein, Richard E. Univ of Illinois Urbana United States

Several decades ago, the principles of dynamic systems and controls were directed towards large engineering structures. In more recent years, the use of feedback control systems technology has been introduced to cause a structure to be `smart,' or to be semi-actively controlled. As structural control matures, and such things as `intelligent' structures and `smart' systems methodology become understood and accepted in the broader scientific and technical circles, the uttering of some thoughts in reflection becomes appropriate. The paper recounts the author's personal role and experiences, examines trends and underlying issues in structural control, and concludes with admonitions, recommendations and visions concerning future directions in structural control.

关键词： Intelligent structures

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control design which respects characteristic length scales in smart systems and smart structures

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Proceedings of SPIE - The International Society for Optical Engineering 1999年 3667卷 202-210页

作者： Baillieul, J. Boston Univ Boston United States

Although there is a mature and continually growing body of knowledge concerning the ways in which the dynamics of fluids and solids depend on characteristic length scales, current theories governing control design do not take explicit account of length scales. Recent research has demonstrated the need to take such considerations into account in designing control systems for smart materials and smart structures in which the goal is to employ small-scale actuators and sensors with characteristic length scales in the micron to millimeter range. For many applications, sensors and actuators will need to be separated by considerable distances (in terms of characteristic length scales). Closed loop feedback designs in this setting may involve communications delays, and both the communications channels and the sensors themselves will typically be relatively noisy. Hence traditional approaches to the design of feedback control laws need to be rethought and modified to work effectively in the noisy, nonlinear, bandlimited world of microelectromechanical systems (MEMS). This paper discusses one approach to a robust, length-scale respecting theory of control based on oscillatory actuation. It includes a brief outline of recent developments in the control of mechanical systems using oscillatory actuation, emphasizing the dependence on characteristic length scales. The principal applications with which we are working are micro-pendulum designs, micro-piston actuators for deformable mirrors as well as micro-valves for the control of fluid-structure boundary layer control.

关键词： Intelligent structures

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