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smart structures and materials 1999 Conference

作者： Kim, YS Kim, I Lee, C Moon, CY Kumoh Natl Univ Technol Sch Mech Engn Kumi 730701 Kyungbuk South Korea

ISBN: (纸本)0819431419

This paper presents a methodology to suppress the vibration of thin rectangular plate clamped all edges. Intelligent materials such as the piezoelectric ceramic are used as actuators and sensors. The experimental modeling technique, i.e., the state-space frequency domain identification, is introduced to model the complex shaped structures bonded with noncollocated actuators/sensors. This method is much free from the Multi-Input Multi-Output (MIMO) model order problem caused at the digital implementation and also reduces distortion of the signal. In control scheme, the adaptive feedforward with feedback control algorithm is adopted since it is robust for both the transient and persistent external disturbances. The adaptive feedforward control uses the well known Multiple filtered-x LMS(least mean square) algorithm. The MIMO error path dynamics is controlled by the feedback loop which is constructed by multivariable digital LQG(Linear Quadratic Gaussian) controller composed of the regulator and Kalman filter. Experiment results demonstrate the effective reduction of the vibration label and the robustness for both the transient and persistent external disturbances.

关键词： active control piezoelectric optimal control feedforward Kalman filter

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Optimal vibration control of adaptive-aircraft wings carrying externally mounted stores and exposed to blast loading

Optimal vibration control of adaptive-aircraft wings carryin...

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smart structures and materials 1999 Conference

作者： Na, S Librescu, L Korea Polytechn Univ Dept Automat Engn Keongki Do 429450 South Korea

ISBN: (纸本)0819431419

A study of optimal vibration control of aircraft wings carrying externally mounted stores and exposed to blast loading is presented. The wing structure is modelled as a thin-walled beam of closed cross-section contour, and a number of non-classical features such as transverse shear, secondary warping, and anisotropy of the constituent materials are included. The wing structure can carry underwing and/or tip stores. The control is achieved via the use of actuating and sensing-capabilities provided by piezoelectric devices which are bonded or embedded into the host structure. The cases of piezoactuators spread over the entire span of the structure, or in the form of a patch are considered, and issues related with the influence of patch location and size upon the vibration control efficiency of wings carrying external stores are discussed. Other issues related with the minimization of the required input power and of those generated by the inclusion/discard in the quadratic performance index of time-dependent external excitations are also addressed.

关键词： optimal control dynamic response aircraft wings external stores piezopatch piezoactuators

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Matrix method for analyzing structural-acoustic power efficiency

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Proceedings of SPIE - The International Society for Optical Engineering 1999年 3667卷 512-523页

作者： Cao, Renfang Leo, Donald J. Virginia Polytechnic Inst and State Univ Blacksburg 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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Stiffness of smart composites with shape memory alloy fibers in the presence of matrix cracks

Stiffness of smart composites with shape memory alloy fibers...

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smart structures and materials 1999 Conference

作者： Birman, V Univ Missouri Engn Educ Ctr St Louis MO 63121 USA

ISBN: (纸本)0819431419

The paper presents a methodology for evaluating the effective stiffness of unidirectional composite materials with shape memory alloy (SMA) fibers in the presence of matrix cracks. The solution is obtained for the case where SMA fibers in the intact composite are in the austenitic phase. However, elevated stresses in the sections of SMA fibers adjacent to the crack planes cause the martensitic transformation affecting the stiffness of the material. The solution has to account for thermal residual stresses in SMA and "ordinary" fibers and in the matrix. The order of magnitude of these stresses is calculated in the paper for two representative composite systems. As follows from the numerical examples, thermal residual stresses in the SMA fibers increase proportionally to their volume fraction but remain relatively small. However, thermal stresses in the matrix may reach rather high values reducing the strength of the matrix by a significant factor.

关键词： shape memory alloy composites matrix cracks stress-induced phase transformation residual thermal stresses

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Dynamic model reduction for control of molecular beam epitaxy

Dynamic model reduction for control of molecular beam epitax...

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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

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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