INTERACTIVE CONTROL-SYSTEM DESIGN BY A MIXED H-INFINITY-PARAMETER SPACE METHOD

This paper presents an interactive graphical method to determine sets of stabilizing controllers satisfying any combination of constraints o n the sensitivity, complementary sensitivity, and input sensitivity tr ansfer functions. The method is limited to single-input/single-output systems but offers significant advantages over current H-infinity meth ods. It can handle pure time delays in an exact manner. The weighting functions need not be rational. By virtue of producing the required pa rameter space region for the frequency response criteria, subsequent d irect time-domain optimization is possible. The controllers obtained a re of lower order for comparable performance than those produced by cu rrent H-infinity techniques. The method is particularly well suited to robust control problems, where frequency-domain constraints emerge fr om the analysis of uncertainties in the system, and also to suboptimal problems, where the frequency-domain loop shaping is used to achieve time-domain specifications.