On the step wise Hurwitz property: a new tool for robust output feedback stabilization

A new theoretical concept is introduced for polynomials: the stepwise Hurwitz property. Subsequently, it is shown how this concept can be used to systematically achieve robust output feedback stabilization for large classes of uncertainty structures. A principal motivation for this paper is the fact that the state feedback controller construction methods do not readily admit modifications to handle the output feedback case. One of the fundamental technical issues addressed in this paper involves the handling of poles and zeros at the origin. For example, high-gain control results which are available to robustly stabilize an uncertain minimum phase plant G(S,q) via output feedback, do not readily extend to plants of form s/sup m/G(s,q).