Identification of frequency domain models for nonlinear systems
ABSTRACT This paper presents a computer-aided engineering approach for identification of linear models from a set of frequency response data. The approach is based on a new system identification technique. The primary intention of the developed system identification technique and the associated software is to identify linear models for nonlinear systems whose input/output behaviour is characterized by their corresponding sinusoidal-input describing function models. However, the technique may also be applied to identification of linear models from experimental frequency response data. At present, the identification approach and the associated software is limited to single-output, linear, deterministic, and time-invariant systems. A computer-aided engineering environment based on the developed system identification technique has also been developed. The software is developed on a Harris-800 super-minicomputer and a Tektronix 4115B high resolution, raster, and color graphics terminal.
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ABSTRACT: In this paper, a systematic procedure for design of a combustion chamber pressure control system is presented. The procedure is applied to a typical liquid propellant engine and the performance of the resulting new control system is compared with that of the present one. In this research, the nonlinear and dynamic mathematical model of the engine, which includes both soft and hard nonlinearities, is used. The systematic controller design procedure is based on describing function models of the engine coupled with the factorization theory.
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ABSTRACT: A new versatile software utility for synthesis of linear PID controllers is described, and the software listing is presented. The software is in the MATLAB environment. Closed-form PID controller gain design equations are developed. The design approach is systematic, and it is based on frequency matching technique with a model matching criteria. The objective is to design a closed-loop feedback system with a PID controller whose dynamic and static behavior would mimic a user-defined reference linear model. The design procedure is automated via a new MATLAB command. The software also has applications in synthesis of nonlinear PID controllers. Because the design equations are of a closed form, the speed of calculations is high; therefore, design software may be used in designing self-tuning adaptive PID controllers.Advances in Engineering Software 09/2003; 34(9):551-557. DOI:10.1016/S0965-9978(03)00062-0 · 1.42 Impact Factor
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ABSTRACT: In this paper a new systematic controller synthesis methodology for use with highly nonlinear multivariable and nonautonomous systems with application to a class of multivariable nonlinear aerospace systems is presented. The procedure is applied to a typical liquid propellant engine, and the performance of the resulting new control system is presented. In this research, the nonlinear dynamic model of the engine, which includes both soft and hard nonlinearities, is developed. The systematic controller design procedure is based on describing function models of the engine coupled with a new multivariable exact model matching procedure.Journal of Dynamic Systems Measurement and Control 09/2004; 126(3). DOI:10.1115/1.1789975 · 1.04 Impact Factor