Robust output feedback stabilization for two new uncertainty structures

In this technical note, we provide two new uncertainty structures for linear systems which admit robust output feedback stabilization. These structures are characterized by having poles or zeros at the origin. Ourmethod is motivated by the fact that high-gain control results available to robust output feedback stabilization of an uncertain minimum phase plant G(s,q) do not readily extend to plants of the form s^mG(s,q). We also show that upper and lower triangular uncertainty structures in the state space, considered by many authors in the context of recursive construction of Lyapunov functions and state feedback controls, are special cases of the structures considered in this technical note.