VARIABLE STRUCTURE ADAPTIVE POLE PLACEMENT CONTROL FOR UNCERTAIN SYSTEMS: AN INTERVAL APPROACH

摘要

This paper presents the design of a robust pole placement controller for linear and time invariant systems described by models whose parameters are unknown but with known bounds, using only plant input and output signals. The main objective is to locate the closed-loop poles within a region specified by an interval characteristic polynomial, chosen based on performance specifications and whose stability is guaranteed by Kharitonov's theorem. The procedure to find a closed interval for each controller parameter is formulated as a nonlinear programming (NLP) problem and switching laws based on the variable structure adaptive pole placement control (VS-APPC) are used to estimate the unknown plant parameters. This innovative strategy gives a fast and non-oscillatory transient, smooth control signal and robustness to large model parameter variations. Moreover, the constraints imposed by the interval controller meet the closed-loop performance requirements. Simulation results are presented for second order nonminimum phase plants, to illustrate the properties of the proposed technique.