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smart structures and materials 1999 Conference

作者： Ramanathan, S Zhu, B Chang, W Varadan, VV Varadan, VK Penn State Univ Res Ctr Engn Elect & Acoust Mat CEEAM University Pk PA 16802 USA

ISBN: (纸本)0819431427

Electro-active polymer actuators (EAPA) have been a topic of research interest in the recent decades due to their ability to produce large strains under the influence of relatively low electric fields as compared to commercially-available actuators. This paper investigates the feasibility of Electro-Active Polymer Actuators (EAPA) for active and passive cabin noise control. The passive damping characteristics of EAPA were determined by measuring the transmission loss of four samples of various thickness and composition in an anechoic chamber in the 200-2000Hz frequency range. This was then compared to that of Plexiglas and silicone rubber sheets of comparable thickness. The transmission loss of EAPA and Plexiglas were observed to be the about the same. The transmission loss of EAPA was greater than that of silicone rubber, of the same thickness. The experimental and theoretical results computed using the mass law agree well. EAPA produces a strain of 0.006 for an applied field of 1 Vm. The ability of EAPA to potentially provide active as well as passive damping in the low to intermediate frequency range, along with being light-weight, pliable and transparent, makes it attractive for noise control applications as active/passive windows or wall papers.

关键词： electro-active polymer actuators transmission loss cabin noise control

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Wavelet control model of suppressing vibration of beam-plates with piezoelectric sensors and actuators

Wavelet control model of suppressing vibration of beam-plate...

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Proceedings of the 1999 smart structures and materials - mathematics and control in smart structures

作者： Zhou, You-He Wang, Jizeng Zheng, Xiaojing Jiang, Qing Lanzhou Univ Gansu China

A dynamic control model of suppressing external disturbance to beam-plates with piezoelectric sensors and activators is developed by means of the scaling function transform of the Daubechies wavelet theory. By virtue of this new mathematical tool, an explicit formulation of identification of deflection configuration is expressed in terms of electric charge/current signals measured from piezoelectric sensors. After a control law of negative feedback of the identified deflection and velocity signals is employed, the wavelet Galerkin method or wavelet weighted residual method is used to determine a distribution of control voltage applied on the piezoelectric actuators. Due to that the scaling function transform is like a low-pass filter which can automatically filter out high-order signals of vibration or disturbance from the measurement and the controller employed here, this model does not lead to those undesired phenomena of control instability which is often appeared in a control system and caused by the spilling over of high-order signals from measurement and controller if no special technique is taken in the control system. Finally, a numerical simulation is carried out to show the efficiency and ability of the control programme proposed in this paper. It is found that this control model is more efficient than a control program of convention to the example.

关键词： Intelligent structures

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Whole-spacecraft vibration isolation system for the GFO/Taurus mission

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Proceedings of SPIE - The International Society for Optical Engineering 1999年 3672卷 175-185页

作者： Johnson, Conor D. Wilke, Paul S. Grosserode, Patrick J. CSA Engineering Inc Mountain View United States

ISBN: (纸本)081943146X

A whole-spacecraft isolation system for the GFO/Taurus mission was designed, fabricated, tested, and subsequently flown on February 10, 1998. This isolation system was designed to reduce dynamic responses on the GFO spacecraft caused by the resonant burn dynamic load introduced by the Castor 120 solid rocket motor. Longitudinal (flight direction) response of the GFO spacecraft center of gravity, due to the resonant burn load, was reduced by a factor of seven. The isolation system design was very nonintrusive to existing hardware, lightweight, and effective. Flight data indicates that the isolation system performed as designed. The GFO spacecraft had a successful launch and is currently operational on-orbit. A second flight of this type of isolation system occurred in October 1998. Similar isolation systems are planned for other flights in 1999 and 2000. This whole-spacecraft isolation technology was highly successful for the GFO/Taurus mission.

关键词： Vibration control

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Effects of modeling assumptions on loss factors predicted for viscoelastic sandwich beams

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Proceedings of SPIE - The International Society for Optical Engineering 1999年 3672卷 251-262页

作者： Austin, Eric M. Inman, Daniel J. Virginia Polytechnic Inst & State Univ Blacksburg United States

The concept of enhancing energy dissipation in thin beams and panels by adding viscoelastic materials to a structure dates back at least to the early 1950's. Kerwin in 1959 was the first to present a general analysis of viscoelastic material constrained by another metal layer. He made several key simplifying assumptions in the mathematics, as did DiTaranto (1965) and Mead and Markus (1969) in follow-up studies: 1) the constraining layer bends in the transverse direction exactly as the base layer, 2) the viscoelastic layer undergoes pure shear, and 3) the viscoelastic layer does not change its thickness during deformation. While appropriate for damping problems of that time, the role of passive, and now active, damping has expanded in the decades since to the point that many problems of practical engineering interest are no longer represented well by these mathematical models. This paper explores a few pitfalls of simplified modeling through some trade studies using benign-looking sandwich beams. The Mead and Markus assumptions are implemented using finite elements and are compared to a beam comprised entirely of higher order elements. A sandwich beam is also modeled using Euler-Bernoulli beams (acting independently) as facesheets and a linear element for the viscoelastic material, similar to how a sandwich might be modeled using standard elements in a commercial code. The accuracy of damping predictions is inferred from the accuracy of strain energy distributions.

关键词： Vibration control

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Design of flextensional transducers using the homogenization design method

Design of flextensional transducers using the homogenization...

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Proceedings of the 1999 smart structures and materials - mathematics and control in smart structures

作者： Silva, Emilio C.N. Nishiwaki, Shinji Kikuchi, Noboru Universidade de Sao Paulo Sao Paulo Brazil

Flextensional transducers consist of a piezoceramic (or a stack of piezoceramics) connected to a flexible mechanical structure that converts and amplifies the output displacement of the piezoceramic. Among the applications, they can be used as actuators and sonars. The transducer performance in these applications depends on the distribution of mass, stiffness, and flexibility in the coupling structure domain, which is related to the coupling structure topology. By designing other types of coupling structures connected to the piezoceramic, we can obtain new types of flextensional transducers with enhanced performance for a desired application. In this work, we extended the method for designing flextensional transducers in static and low-frequency applications to dynamic applications by introducing the inertia effect in the optimization problem. The method applies topology optimization technique based on the homogenization design method, which consists of finding the optimal material distribution in a perforated design domain with infinite microscale voids. The problem is posed as the design of a flexible structure coupled to the piezoceramic that produces high output displacements in a specified point of the domain and direction, in a specified frequency. Therefore, it consists of designing a flexible structure with a specified mode shape in a desired resonance frequency. As a result, designs of flextensional transducers are presented.

关键词： Intelligent structures

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Hubble Space Telescope solar array damper

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Proceedings of SPIE - The International Society for Optical Engineering 1999年 3672卷 186-197页

作者： Maly, J.R. Pendleton, S.C. Salmanoff, J. Blount, G.J. Mathews, K. CSA Engineering Mountain View United States

This paper describes the design of a solar array damper that will be built into each of two new solar arrays to be installed on the Hubble Space Telescope (HST) during Servicing Mission 3. On this mission, currently scheduled for August, 2000, two `rigid' solar array wings will replace the `flexible' wings currently providing power for HST. In addition to increased power, the new arrays will provide the capability for HST to survive re-boost to a higher orbit. The objective of the damper is to reduce the dynamic interaction of these new wings with the Telescope spacecraft. The damper, which is integral to the mast of the solar array, suppresses the fundamental bending modes of the deployed wings at 1.2 Hz (in-plane) and 1.6 Hz (out-of-plane). With the flight version of the damper, modal damping of 2.3% of critical is expected over the temperature range of -4 °C to 23 °C with a peak damping level of 3.9%. The unique damper design, a combination of titanium spring and viscoelastic damper, was developed using a system finite element model of the solar array wing and measured viscoelastic material properties. Direct complex stiffness (DCS) testing was performed to characterize the frequency- and temperature-dependent behavior of the damper prior to fixed-base modal testing of the wing at NASA/Goddard Space Flight Center (GSFC).

关键词： Vibration control

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Satellite Ultraquiet Isolation Technology Experiment (SUITE): Electromechanical subsystems

Satellite Ultraquiet Isolation Technology Experiment (SUITE)...

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Proceedings of the 1999 smart structures and materials - Industrial and Commercial Applications of smart structures Technologies

作者： Anderson, Eric H. Evert, Michael E. Glaese, Roger M. Goodding, James C. Pendleton, Scott C. Camp, Donald Fumo, John Jessen, Marty Cobb, Richard G. Erwin, R.Scott Jensen, Jonathan CSA Engineering Inc Mountain View CA United States

Spacecraft carry instruments and sensors that gather information from distant points, for example, from the Earth's surface several hundred kilometers away. Small vibrations on the spacecraft can reduce instrument effectiveness significantly. Vibration isolation systems are one means of minimizing the jitter of sensitive instruments. This paper describes one such system, the Satellite Ultraquiet Isolation Technology Experiment (SUITE). SUITE is a piezoelectric-based technology demonstration scheduled to fly in 2000 on PICOSat, a microsatellite fabricated by Surrey Satellite Technology, Ltd. control from the ground station is planned for the first year after launch. SUITE draws on technology from previous research programs as well as a commercial piezoelectric vibration isolation system. The paper details the features of SUITE, with particular emphasis on the active hexapod assembly. A description of the PICOSat spacecraft and the other considerations preceding the development of the flight hardware begins the paper. Experiment goals are listed. The mechanical and electromechanical construction of the SUITE hexapod assembly is described, including the piezoelectric actuators, motion sensors, and electromagnetic actuators. The data control system is also described briefly, including the digital signal processor and spacecraft communication. The main features of the software used for real-time control and the supporting Matlab software used for control system development and data processing are summarized.

关键词： Intelligent structures

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Whole-spacecraft vibration isolation system for the GFO/Taurus mission

Whole-spacecraft vibration isolation system for the GFO/Taur...

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Proceedings of the 1999 smart structures and materials - Passive Damping and Isolation

作者： Johnson, Conor D. Wilke, Paul S. Grosserode, Patrick J. CSA Engineering Inc Mountain View CA United States

关键词： Vibration control

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Effects of modeling assumptions on loss factors predicted for viscoelastic sandwich beams

Effects of modeling assumptions on loss factors predicted fo...

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Proceedings of the 1999 smart structures and materials - Passive Damping and Isolation

作者： Austin, Eric M. Inman, Daniel J. Virginia Polytechnic Inst & State Univ Blacksburg VA United States

关键词： Vibration control

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smart structures and materials 1998: mathematics and control in smart structures

Smart structures and materials 1998: Mathematics and control...

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smart structures and materials 1998 mathematics and control in smart structures

The proceedings contains 67 papers from the Conference on smart structures and materials 1998: mathematics and control in smart structures. The topics discussed include: smart structure research at the University of Stuttgart;design of fluid-loaded piezoelectric transducers for acoustic power considerations;improved aircraft roll maneuver performance using smart deformable wings;modeling of polarization switching in piezoceramics and stress intensification due to polarization switching.

关键词： Intelligent structures

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