Computer-aided optimisation of simplified discrete models for control systems

Abstract

A computer-aided method for the computation of optimal discrete models with reduced orders for control systems is presented in this paper. The method used for simplification utilises a time-domain-optimisation technique to search for optimum values for the parameters of prespecified reduced-order discrete-time models for control systems. The measure of success of simplification is taken to be the minimum integral squared error between the step responses of the simplified discrete-time models and that of the actual system at sampling instants. Two examples are considered to illustrate the usefulness of the method in simplifying control systems given in various forms. One of the examples considered was to obtain reduced-order discrete-time models for a fourth-order Butterworth filter. The method proved to be powerful in finding the optimal discrete models with reduced orders for both short and long sampling periods.