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smart structures and materials 2000 - mathematics and control in smart structures

作者： Brueckner, Steffen Rudolph, Stephan Universitaet Stuttgart Stuttgart Germany

For nonlinear and adaptive control of smart structures direct and indirect neural network control strategies have been suggested. In indirect neural network control the identified plant models are usually implemented as black-box neural networks using no a priori knowledge. Designing a neural network for system identification using dimensional analysis results in neural networks, where in contrary to black-box solutions no dimensionally inhomogeneous states can occur. Furthermore, the generalization and learning properties of neural networks designed using dimensional analysis are usually improved compared to conventional black-box networks. This work describes a technique of using neural networks for system identification and control, where the neural network has been constructed according to a dimensional analysis of the governing equations.

关键词： Intelligent structures

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Electromagnetic forces for a new vibration control system: experimental verification

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smart materials & structures 2000年第2期9卷 127-131页

作者： Matsuzaki, Y Ikeda, T Nae, A Sasaki, T Nagoya Univ Dept Aerosp Engn Chikusa Ku Nagoya Aichi 4648603 Japan

In our previous work we proposed a new concept of the control system in which vibrations of a partially magnetized thin beam are actively suppressed using electromagnetic forces induced by an electric current conducted through the beam. In this experimental study we will demonstrate the effectiveness of the electromagnetic force which plays a major role in our new vibration control system. As a partially magnetized beam is not available at the present moment, a magnetic field generated by a permanent magnet is used to control the motion of a thin elastic beam on which an electric current is conducted through an electric wire glued onto the beam's surface across its breadth. The objective of the present study is to examine if an actually induced electromagnetic force acting on the electric wire is effective in suppressing the beam's vibrations. A feedforward control analysis of the corresponding experiment is performed to confirm experimental results.

关键词： Beams and girders

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Closed-loop hover test results with a neurocontroller on piezoactuated smart rotor blades

Closed-loop hover test results with a neurocontroller on pie...

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smart structures and materials 2000 Conference

作者： Spencer, MG Sanner, RM Chopra, I Univ Maryland Dept Aerosp Engn Alfred Gessow Rotorcraft Ctr College Pk MD 20742 USA

ISBN: (纸本)0819436038

On-blade smart structure actuators are capable of actively altering the aerodynamic loads on rotor blades. With a suitable feedback control law, such actuators could potentially be used to counter the vibrations induced by periodic aerodynamic loading on the blades with lower weight penalties than the previous actuation methods and without the bandwidth constraints. This paper covers the development and testing of a new, robust individual blade control (IBC) methodology for rotor vibration suppression using piezo actuated trailing edge flaps and active twist tip rotors. The controller uses a neural network to learn to actuate the trailing edge flap thus adaptively suppressing the blade or hub vibrations. In this application, no offline training is performed. Instead, a neural network is used in real time to adaptively command the actuator deflections thus reducing vibrations. Closed loop experimental tests with piezo actuated scale rotor systems were conducted on the University of Maryland hover test stand. The results include two different Mach scale smart rotor systems (trailing edge flaps and active tip twist) that were controlled by the same adaptive neurocontrol algorithm. These tests demonstrate the controller's robust ability to successfully learn to control the rotor vibrations with no a priori information about the blade/actuator structure or the aerodynamic loading.

关键词： Actuators Neural networks Aerodynamics control systems Algorithm development Filtering (signal processing) Data acquisition Vibration control smart structures Servomechanisms

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Detecting damage in non-uniform beams using the dereverberated transfer function response

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smart materials & structures 2000年第4期9卷 429-444页

作者： Purekar, AS Pines, DJ Univ Maryland Dept Aerosp Engn Smart Struct Lab College Pk MD 20742 USA

Delamination damage in composite rotorcraft flexbeams caused by excessive vibratory and fatigue loads can lead to degradation in flapwise and lagwise performance of the rotor blade. In addition, delaminations can result in rapid fatigue failure of these tailored composite elements leading to catastrophic results. A novel damage detection strategy is evaluated in this work which attempts to exploit the dereverberated transfer function response of beams with tapered geometries. This approach avoids high fidelity finite element models of damaged one-dimensional beams with non-uniform geometries. To obtain the dereverberated transfer function response, a virtual control force is applied to the reverberated transfer function response to remove resonant and anti-resonant dynamics associated with the beam's boundary conditions. Magnitude and phase characteristics between each actuator and sensor can then be used to infer changing structural properties. Analytical and experimental results suggest that this approach can be used to quantitatively and qualitatively infer delamination damage in non-uniform beams. Experimental results are displayed for beams with varying thickness and width tapers.

关键词： Composite beams and girders

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Modeling of smart composites controlled by thin piezoelectric fibers

Modeling of smart composites controlled by thin piezoelectri...

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smart structures and materials 2000 - mathematics and control in smart structures

作者： Gabbert, Ulrich Koeppe, Heinz Fuchs, Karl Seeger, Falko Univ of Magdeburg Germany

Recently, thin piezoelectric fibers with diameters between 10μm and 30μm have been manufactured and used as sensor/actuator components of smart composite structures. The paper deals with the mathematical analysis, numerical simulation and optimal design of smart structures controlled by such thin piezoelectric fibers, where two different approaches are investigated. At first a smeared concept is applied. Each active layer consisting of piezoelectric fibers embedded in a matrix material is modeled as an anisotropic coupled electro-mechanical continuum and analyzed by recently developed special finite shell elements. At second a discrete concept is used, where the piezoelectric fibers are modeled as one-dimensional truss like finite elements which are embedded into conventional finite elements by a penalty technique. These two approaches are discussed and compared.

关键词： Intelligent structures

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Modeling and experimentation of a positioning system of SMA wires

Modeling and experimentation of a positioning system of SMA ...

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smart structures and materials 2000 Conference

作者： Lei, KF Yam, Y Chinese Univ Hong Kong Dept Mech & Automat Engn Intelligent & Control Syst Lab Shatin Hong Kong Peoples R China

ISBN: (纸本)0819436046

This work reports two modeling and control attempts performed on a positioning system comprising of linking SMA wires and an overlooking video system for on-line measurements. The first attempt takes the model by Ikuta and identifies experimentally the parameters of the SMA wire. The identified single wire model is then extended to a system of two SMA wires joining together at their tips, based upon which open loop position control of the linkage is then conducted. The approach, however, becomes too complicated when more SMA wires are involved. The second attempt utilizes a neuro-fuzzy based approach for positioning control of a linkage point joining together four SMA wires. The second approach involves four ANFIS neuro-networks with hybrid learning algorithm trained to model the currents to the SMA wires as functions of present and target positions of the linkage point. Experimentation for both the two-wires and four-wires system yield quite satisfactory performance.

关键词： SMA ANFIS

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Active control of composite box beams using in-plane piezoelectric actuation and structural coupling with optimization

Active control of composite box beams using in-plane piezoel...

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smart structures and materials 2000 Conference

作者： Koldoff, J Chattopadhyay, A Nam, C Arizona State Univ Dept Mech & Aerosp Engn Tempe AZ 85287 USA

ISBN: (纸本)0819436038

An integrated structures/controls optimization is developed for vibration suppression of a composite box beam with surface bonded piezoelectric actuators. The penalty approach is used to perform the multi-objective hybrid optimization to enhance damping of the first lag, flap, and torsion modes while minimizing control input. The objective functions and constraints include damping ratios, and natural frequencies. The design variables include ply orientations of the box beam walls, and the location and size of the actuators. Two box beam configurations are investigated and the results are compared. In the first, piezoelectric actuators are bonded to the top and bottom surfaces and in the second, actuators are bonded to all four walls for additional in-plane actuation. Optimization results show that significant reductions in control input and tip displacement can be achieved in both cases, however, improved response trends are obtained with in-plane actuation.

关键词： adaptive structures integrated design structures/controls optimization

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Active noise suppression of smart panels including piezoelectric devices and absorbing materials

Active noise suppression of smart panels including piezoelec...

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smart structures and materials 2000 - mathematics and control in smart structures

作者： Kim, Jaehwan Im, Byoung-Soo Lee, Joong-Guen Univ of Inha Korea Republic of

In this paper, noise reduction performance of piezoelectric smart panels is experimentally studied. Piezoelectric smart panel is comprised of plate structure on which piezoelectric sensor/actuators are bonded and sound absorbing materials. The concept of piezoelectric smart panels is to combine passive and active strategies such that the noise reduction can be effectively achieved over a broad frequency range. The noise reduction performance is tested on an acoustic tunnel. The tunnel is made of a guided tube having a square cross section and loud speaker is installed at one end as a sound source while nonreflection terminator is attached at the other end. The panels can be mounted in the middle of the tunnel and the transmission as well as reflection of panels can be measured. Noise reduction performance of a single plate with absorbing material shows a good result at mid frequency region but little effect in the resonance frequencies. When the active control scheme is activated, a remarkable noise reduction is observed at the resonance. The combined use of absorbing materials and piezoelectric active devices brings the simultaneous noise reduction in mid and low frequency regions. It can be concluded that piezoelectric smart panels incorporating passive absorbing material and active piezoelectric devices, is a promising technology for noise reduction in a wide band frequency.

关键词： Intelligent structures

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smart fluid damping: Shaping the force/velocity response through feedback control

Smart fluid damping: Shaping the force/velocity response thr...

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smart structures and materials 2000 Conference

作者： Sims, ND Stanway, R Johnson, AR Peel, DJ Bullough, WA Univ Sheffield Dept Engn Mech Sheffield S1 3JD S Yorkshire England

ISBN: (纸本)0819436038

It is now well known that smart fluids (electrorheological (ER) and magnetorheological (MR)) can form the basis of controllable vibration damping devices. With both types of fluid, however, the force / velocity characteristic of the resulting damper is significantly non-linear, possessing the general form associated with a Bingham plastic. In a previous paper the authors showed that by using a linear feedback control strategy it is possible to produce the equivalent of a viscous damper with a continuously variable damping coefficient. In the present paper the authors illustrate an extension of the technique, by showing how the shape of the force / velocity characteristic can be controlled through feedback control. This is achieved by using a polynomial function to generate a set point based upon the damper velocity. The response is investigated for polynomial functions of zero, 1(st) and 2(nd) order. It is shown how the damper can accurately track higher order polynomial shaping functions, whilst the zero order function is particularly useful in illustrating the dynamics of the closed-loop system.

关键词： smart fluids electrorheological magnetorheological feedback damping linearisation

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control and response characteristics of a magneto-rheological fluid damper for passenger vehicles

Control and response characteristics of a magneto-rheologica...

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smart structures and materials 2000 Conference

作者： Choi, SB Lee, HS Hong, SR Cheong, CC Inha Univ Dept Mech Engn Inchon 402751 South Korea

ISBN: (纸本)0819436038

This paper presents control characteristics of a semi-active magneto-rheological (MR) fluid damper for a passenger vehicle. A cylindrical MR damper is devised and its governing equation is derived. After verifying that the damping force of the MR damper can be continuously tuned by the intensity of the magnetic field, PID controller is employed to achieve the desired damping force. The proposed MR damper is then applied to a full-car model and performance characteristics of the full-car such as vertical acceleration of the body are evaluated via hardware-in-the-loop-simulation(HILS).

关键词： MR damper vibration control vehicle suspension HILS

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