An important problem in the applications is the controllability for perturbed systems. A special kind of perturbed systems, depending on a small parameter (epsilon) is the wave equation when the coefficients are rapid...
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ISBN:
(纸本)0819411523
An important problem in the applications is the controllability for perturbed systems. A special kind of perturbed systems, depending on a small parameter (epsilon) is the wave equation when the coefficients are rapidly oscillating or when posed in periodically perforated domains. Then a limit system (in the homogenization theory sense) can be defined. We present here a review of some recent results for exact and approximate controllability in these situations.
The ACTEX flight experiment is scheduled for launch and to begin its on orbit operations in early 1994. The objective of the ACTEX experiment is to demonstrate active vibration control in space, using the smart struct...
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ISBN:
(纸本)0819411507
The ACTEX flight experiment is scheduled for launch and to begin its on orbit operations in early 1994. The objective of the ACTEX experiment is to demonstrate active vibration control in space, using the smart structure technology. This paper discusses primarily the hardware development and program management issues associated with delivering low cost flight experiments.
An electromechanical surface damping (EMSD) technique is proposed. The technique is a combination of the constrained layer damping and the shunted piezoelectric methods, where the viscoelastic layer attached to the su...
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ISBN:
(纸本)0819411523
An electromechanical surface damping (EMSD) technique is proposed. The technique is a combination of the constrained layer damping and the shunted piezoelectric methods, where the viscoelastic layer attached to the surface of the vibrating substructure is constrained by a shunted piezoelectric ceramic element. A mathematical model of the dynamic behavior of the coupled piezoelectric/constrained layer/substructure (EMSD element) is developed, implemented into a finite element algorithm, and used to investigate the effect of some of the system parameters on the dynamic characteristics (the first three natural frequencies and modal loss factors) of a generic cantilever beam. The effect of the following system parameters is considered: storage modulus ratios, material loss factors, thickness ratios, and the axial location of the EMSD element. The algorithm is also used to demonstrate the effectiveness of the proposed EMSD technique in controlling the peak vibration amplitudes at the first two natural frequencies of the cantilever beam.
An integrated means for active controller design and structure redesign is presented. The techniques of covariance control are used to parametrize all possible combinations of active controllers/structure redesign par...
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ISBN:
(纸本)0819411523
An integrated means for active controller design and structure redesign is presented. The techniques of covariance control are used to parametrize all possible combinations of active controllers/structure redesign parameters which can stabilize the plant, and achieve certain closed-loop performance.
A control methodology integrating sliding mode control, distributed parameter systems theory, and fuzzy control is presented for the vibration damping of flexible structures. The method reduces the theoretically infin...
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ISBN:
(纸本)0819411523
A control methodology integrating sliding mode control, distributed parameter systems theory, and fuzzy control is presented for the vibration damping of flexible structures. The method reduces the theoretically infinite-order system to a second-order representation, still capturing its vibratory nature in a series of decentralized input/output loops. A sliding controller is then designed with fuzzy control gain weighting to increase the performance of the system off the sliding surface. The results of computer simulations are presented including comparisons demonstrating superior damping performance to output velocity feedback.
The application of shape memory alloy materials as actuators and sensors in the active control of flexible structures has been extensively reported in the literature. The design of active controllers plays an importan...
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ISBN:
(纸本)0819411523
The application of shape memory alloy materials as actuators and sensors in the active control of flexible structures has been extensively reported in the literature. The design of active controllers plays an important role in the overall development of smartstructures for a given application. To design active controllers for flexible structures, a mathematical representation of the system is needed. The process of constructing a model to describe the vibration properties of a structure based on experimental test data is known as structural identification method. To account for any uncertainties in the structural models and to accomplish good closed loop system performance and noise suppression properties, we have developed robust control design methodologies for flexible structures. We have utilized the eigensystem realization algorithm (ERA) for system identification and linear quadratic Gaussian with loop transfer recovery (LQG/LTR) method for designing robust controllers for a simple cantilever beam test article. The shape memory alloy, NiTiNOL, is used as an actuator. The LQG/LTR method has been modified to accommodate the limited control force provided by the actuators. The closed loop performance of the cantilever beam is experimentally determined for various types of uncertainties. The properties of robust controllers are demonstrated.
Low Authority Threshold control (LATC) is an active control strategy resulting in a piecewise continuous, with respect to time, constant gain control law which may be used for the vibration control of flexible structu...
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ISBN:
(纸本)0819411523
Low Authority Threshold control (LATC) is an active control strategy resulting in a piecewise continuous, with respect to time, constant gain control law which may be used for the vibration control of flexible structures. The LATC optimal control law gains are dependent on the state vector at the time the gains are applied and are defined by a two-point boundary value problem and a set of integral equality constraints. Because an iterative solution technique is required to determine the optimal gains, the real-time implementation of this control law presented certain difficulties. In this work, a neural network system is trained to determine the optimal gains in real-time for each of two experiments: a cantilevered beam and a nonlinear Duffing oscillator. The optimal gains generated by the neural network system are utilized in an LATC rate feedback control law for the vibration control of these systems.
Using an Artificial Neural Network (ANN) trained with the Least Mean Square (LMS) algorithm we have designed a robust linear quadratic regulator for a range of plant uncertainty. Since there is a trade-off between per...
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ISBN:
(纸本)0819411523
Using an Artificial Neural Network (ANN) trained with the Least Mean Square (LMS) algorithm we have designed a robust linear quadratic regulator for a range of plant uncertainty. Since there is a trade-off between performance and robustness in the conventional design techniques, we propose a design technique to provide the best mix of robustness and performance. Our approach is to provide different control strategies for different levels of uncertainty. We describe how to measure these uncertainties. We will compare our multiple strategies results with those of conventional techniques e.g. H∞ control theory. A Lyapunov equation is used to define stability in all cases.
A parallel processor that is optimized for real-time linear control has been developed. This modular system consists of A/D modules, D/A modules, and floating-point processor modules. The scalable processor uses up to...
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ISBN:
(纸本)0819411523
A parallel processor that is optimized for real-time linear control has been developed. This modular system consists of A/D modules, D/A modules, and floating-point processor modules. The scalable processor uses up to 1,000 Motorola DSP96002 floating-point processors for a peak computational rate of 60 GFLOPS. Sampling rates up to 625 kHz are supported by this analog-in to analog-out controller. The high processing rate and parallel architecture make this processor suitable for computing state-space equations and other multiply/accumulate-intensive digital filters. Processor features include 14-bit conversion devices, low input-to-output latency, 240 Mbyte/s synchronous backplane bus, low-skew clock distribution circuit, VME connection to host computer, parallelizing code generator, and look-up-tables for actuator linearization. This processor was designed primarily for experiments in structural control. The A/D modules sample sensors mounted on the structure and the floating-point processor modules compute the outputs using the programmed control equations. The outputs are sent through the D/A module to the power amps used to drive the structure's actuators. The host computer is a Sun workstation. An OpenWindows-based control panel is provided to facilitate data transfer to and from the processor, as well as to control the operating mode of the processor. A diagnostic mode is provided to allow stimulation of the structure and acquisition of the structural response via sensor inputs.
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