In this paper we develop and present new convex synthesis conditions for robust performance in linear time-varying systems, subject to time-varying perturbations. In particular, these results are exact for sensitivity minimization in the presence of multiplicative perturbations. The methods apply to a number of additional robust performance problems and are always both necessary and sufficient when the system plant is periodic. Otherwise, the conditions provided are always sufficient, and a controller can be directly constructed when this condition holds. Key words. uncertain system, time-varying system, discrete-time system, controller synthesis, convex methods, linear matrix inequality AMS subject classifications. 93D09, 93C55, 93B35 PII. S0363012900369630
Carol Pirie, Geir E. Dullerud