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smart structures and materials 1999 Conference

作者： Kan, D Univ Calif Los Angeles Dept Math Los Angeles CA 90024 USA

ISBN: (纸本)0819431419

One important component in the development of many smart structures and microdevices is the growth of thin firms. The control of the growth processes, therefore, is of interest. In the design of a control system for molecular beam epitaxy (MBE), it is important to have simple mathematical models that describe the different growth morphologies that a growing film may exhibit and incorporate atomic-scale information. Of the three types of models currently being considered (atomistic, continuum, and bulk), bulk models have the most interest to control. Still, due to the complexity of such models, however, a model reduction must be carried out to make real-time control possible. A model reduction routine based on a new version of the nonlinear Galerkin methods is proposed and explained for three different bulk models. A total reduction of one-third the number differential equations is obtained.

关键词： model reduction molecular beam epitaxy

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Active vibration control using piezoelectric smart discs

Active vibration control using piezoelectric smart discs

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smart structures and materials 1999 Conference

作者： van Schothorst, G Philips Ctr Mfg Technol NL-5600 MD Eindhoven Netherlands

ISBN: (纸本)0819431419

In high-precision motion systems, like wafer stages and electron microscopes, mechanical vibrations are a major point of concern. Often, these vibrations have small amplitudes (micrometers) and relatively high frequency (> 50 Hz). The so-called smart Disc (a combined piezoelectric actuator and sensor) is a device that might be used to suppress these vibrations actively. The feasibility of the smart Disc concept is investigated, using an experimental set-up, consisting of a double mass-spring system, with two smart Discs. This system has two badly damped resonance modes, to be damped by the smart Disc(s), by means of feedback of the measured local interaction forces to the actuated displacements. The corresponding control problem, is to minimize the vibrations of the two masses, as a result of a disturbing force. With the experimental set-up, some aspects have been investigated. In the modelling phase, the system revealed high-frequent (3 kHz) resonance peaks, which appeared to originate from the smart Disc housings. These dynamics have been identified and taken into account in the control design. Because of these high-frequent dynamics near the Nyquist frequency, and the high gain at that frequency (which is inherent to the smart Disc concept) discrete time effects have been taken into account explicitly. Besides conventional active vibration control strategies, more sophisticated (MIMO H-infinity, discrete time) control design strategies have been applied successfully.

关键词： active vibration control piezoelectric actuators and sensors identification control design digital control

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Crack extension and kinking in piezoceramics

Crack extension and kinking in piezoceramics

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smart structures and materials 1999 Conference

作者： Xu, XL Rajapakse, RKND Univ Manitoba Dept Civil & Geol Engn Winnipeg MB R3E 0V9 Canada

ISBN: (纸本)0819431419

The problem of an isolated crack as well as a crack with a kink in a plane piezoceramic medium is theoretically investigated in this study. The orientation of a crack with respect to the poling direction may be arbitrary. The approaches of Lekhnitskii's complex potentials and distributed dislocation modeling of cracks for elastic solids are extended to formulate the piezoelectric crack problems. For the case of an isolated arbitrarily oriented crack, analytical solutions are obtained for all electroelastic field variables. It is found that a change of crack orientation may alter the trend of toughness variation, and initiate failure along different planes depending on the direction of electrical field. For the case of a kinked crack, it is shown that the problem is reduced to solving three integral equations with the dislocation densities along the kink line as unknowns. The accuracy of the present scheme is confirmed by comparing with the limiting case of elastic solids. The results presented in this study provide important information on electroelastic fields and fracture parameters corresponding to kinked cracks in piezoceramics.

关键词： cracks fracture mechanics kinking piezoelectrics dislocations integral equations stress intensity factors smart structures

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Reduced order modeling for low Reynolds number flow control

Reduced order modeling for low Reynolds number flow control

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smart structures and materials 1999 Conference

作者： Kurdila, AJ Carroll, B Nishida, T Sheplak, M Univ Florida Dept Aerosp Engn Mech & Engn Sci Gainesville FL 32611 USA

ISBN: (纸本)0819431419

This paper presents recent analytical and experimental research to modify and control low Reynolds number flows over prototypical airfoils associated with micro-air-vehicles. The simplified experimental test geometry consists of a meso-scale piezoceramic actuated flap that undergoes peak amplitude displacements of 40 microns. The flap actuator array is designed to modify separation and reattachment location on the airfoil. The location of the reattachment on the upper surface of the prototypical airfoil is measured by an array of MEM's shear stress Sensors located downstream. The focus of this paper is the discussion of the status and applicability of reduced order modeling techniques for the derivation of active feedback flow control strategies for the prototypical active airfoil. Frequently, reduced order models are derived from a library of component fluid. modes which serve as the basis for a low dimensional approximation of the nonlinear Navier Stokes equations. The methdology discussed in this paper differs markedly from these approaches. We derive a technique employing multiresolution and wavelet approximations of nonlinear Volterra series that represent the input-output dynamics of the system. The accuracy of the resultant low-dimensional input-ouput models is validated on a benchmark nonlinear aeroelastic testbed.

关键词： Sensors Microelectromechanical systems Complex systems Wavelets Actuators Performance modeling Systems modeling control systems Feedback control Ferroelectric materials

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Matrix method for analyzing structural-acoustic power efficiency

Matrix method for analyzing structural-acoustic power effici...

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

作者： Cao, Renfang Leo, Donald J. Virginia Polytechnic Inst and State Univ Blacksburg VA United States

This paper describes a general technique to analyze the radiation impedance and actuator power efficiency of an active structure. Using a modal expansion of the structural vibration, the sound power is conveniently expressed as an integration over the surface of the planar structure. Integrating the finite element analysis into the numerical integral makes this technique applicable to any complex geometrical planar structure under arbitrary boundary conditions. As an example, this technique is applied to study of an actuator driving circular plate with an elastic support, which could be used to simulate a rigid piston. The radiation impedance and power efficiency of this active structure are studied using eigenvalue decomposition. Using general eigenvalue decomposition, the efficiency of air acoustic arrays are also analyzed. A dynamic model of the actuator is introduced to above studies by taking into account the coupling of the actuator and its host structure. Numerical results demonstrate that the radiation impedance of rigid-body motion is comparable to the analytical solution of a baffled rigid piston. Power efficiency studies demonstrate that one or two actuators will generate high efficiency when the rigid-body modes are dominant and more actuators are needed to improve the efficiency if the flexible modes are dominant. The efficiency is related to the structure impedance. A relatively soft actuator will generate a higher efficiency at low frequencies and low efficiency at higher frequencies. In contrast, a relatively stiff actuator will have a moderate efficiency at higher frequencies.

关键词： Acoustic variables control

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Active position control of a shape memory alloy wire actuated composite beam

Active position control of a shape memory alloy wire actuate...

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smart structures and materials 1999 Conference

作者： Song, GB Kelly, B Agrawal, BN Univ Akron Dept Mech Engn Akron OH 44325 USA

ISBN: (纸本)0819431419

This paper presents the design and experiment results of active position control of a shape memory alloy (SMA) wires actuated composite beam. The composite beam is honeycomb structured with shape memory alloy wires embedded in one of its phase sheet for active actuation. The potential applications of this experiment include thermo-distortion compensation for precession space structure, stern shape control for submarines, and flap shape control for aeronautical applications. Shape memory alloy wires are chosen as actuating elements due to their high recovery stress (maybe >700 MPa) and tolerance to high strain (up to 8%). However, shape memory alloy wires are inherently nonlinear and pose a challenge for control design. A robust controller is designed and implemented to active control the tip position of the composite beam. The experiment setup consists of the composite beam with embedded SMA wires, a programmable current/voltage amplifier to actuate the SMA wires, an infrared laser range sensor to detect the beam tip displacement, and a real-time data acquisition and control system. Experiments demonstrated the effectiveness of the robust control.

关键词： shape memory alloy position control robust control real-time control nonlinearity compensation composite beam SMA wire actuator

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Nonlinear oscillations of a plate with piezoceramic patches

Nonlinear oscillations of a plate with piezoceramic patches

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smart structures and materials 1999 Conference

作者： Balachandran, B Zhao, MX Univ Maryland Dept Mech Engn College Pk MD 20742 USA

ISBN: (纸本)0819431419

Nonlinear oscillations of a thin, isotropic panel bearing piezoceramic patches are-studied in this. work. The thin panel, which is clamped along all four edges, forms one of the boundaries of an enclosure. Rigid walls form the other boundaries of the enclosure. The piezoceramic patches are located symmetrically on the top and bottom surfaces of the flexible panel. Nonlinear relationship between the free strain experienced by a piezoceramic patch and the applied electric field is considered along with panel nonlinear elasticity to derive the equations of motion of the plate-enclosure system. It is shown that a voltage input into a piezoceramic actuator pair results in both parametric and external excitations to the panel. For harmonic excitations, the features of the nonlinear responses obtained in the simulations show good agreement with related experimental results. It is seen that for the cases considered, the actuator nonlinearities have a stronger influence on the response than the panel nonlinear elasticity.

关键词： nonlinear oscillations piezoceramic actuator acoustics control actuator nonlinearities

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Nonlinear control of PZT actuated trailing edge flaps

Nonlinear control of PZT actuated trailing edge flaps

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smart structures and materials 1999 Conference

作者： Kurdila, A Li, J Fulton, M Webb, G Univ Florida Dept Aerosp Engn Mech & Engn Sci Gainesville FL 32611 USA

ISBN: (纸本)0819431419

While PZT exhibits only mild nonlinear response at low voltage levels, it is well-known that the response can be profoundly nonlinear at high field strengths. Moreover, the use of mechanical linkages and structural design to amplify the stroke of PZT-based actuation likewise can couple with this material nonlinearity:to yield a structural level nonlinearity that is non-negligible. In this paper, we investigate such a nonlinear response in a PZT actuated trailing edge nap attached to a scaled helicopter rotor blade. While the example studied in this paper is quite specific, the methodology derived is generally applicable. We extend the recent results of [18,19] for the derivation of closed loop control for active material actuated devices. In this technique, a compensator derived hem an offline identification of a Krasnoselski-Pokrovski hysteresis operator is cascaded with the plant. We show that the methodology is well-posed for the class of problems under consideration;we derive closed loop stability and robustness conditions that can be associated with the prediction error in the identified hysteresis operator. We study the performance of our methodology in numerical examples and discuss relevant experimental results.

关键词： Actuators Ferroelectric materials Nonlinear control Complex systems control systems Aerodynamics Nonlinear response Feedback control Kinematics Performance modeling

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Robust, compact and inexpensive analog controllers for cabin noise control

Robust, compact and inexpensive analog controllers for cabin...

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smart structures and materials 1999 Conference

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

ISBN: (纸本)0819431419

Active Noise control has been an area of research interest in the recent decades with the goal of providing reduced noise levels in automobile and aircraft enclosures. Although digital controllers are adaptable and efficient, they lack the simplicity of analog controllers due to the requirement of a computer, D/A and A/D boards. Analog controllers on the other hand can be designed to be compact using current IC technology and hence are relatively very cheap. The following paper studies the application of an analog robust controller to abate the noise radiated into a non-reverberant wooden enclosure by a clamped aluminum plate. Since only the odd-odd modes radiate efficiently, a SISO robust analog controller was designed and built inexpensively for a piezoelectric actuator and accelerometer sensor placed at the center of the plate. A reduction of 17dB is observed when the panel is excited at its fundamental frequency, the dominant radiating mode. When the plate is excited with narrowband noise (40-316Hz), the controller reduces the noise levels in the enclosure by 9dB. The experimental results agree well with the controller simulation carried out using MATLAB

关键词： cabin noise control robust control analog controller

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Satellite Ultraquiet Isolation Technology Experiment (SUITE): Electromechanical subsystems

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Proceedings of SPIE - The International Society for Optical Engineering 1999年 3674卷 308-328页

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 United States

ISBN: (纸本)0819431486

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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