ROBUST OUTPUT-FEEDBACK STABILIZING CONTROL FOR DISCRETE UNCERTAIN SISO SYSTEMS

Given a discrete-time uncertain single-input\single-output (SISO) syst em, matched uncertainties, and a measured output, a necessary and suff icient condition is given for the existence of a min-max output feedba ck stabilizing controller. The existence problem of an output stabiliz ing controller for uncertain systems was treated extensively and solve d for the continuous case, but it remained open for the discrete-time case. It turns out that in contrast to the continuous case, the discre te-time system is required to be neither discrete strictly positive re al nor even minimum phase and still may satisfy the existence conditio ns. The paper also contains some new results on discrete positive real functions.