Observer-based Control of Uncertain Linear Systems: Recovering State Feedback Robustness Under Matching Condition

In this paper we study the problem of observer design for a class of state-feedback controllers that includes high-gain linear control, continuous approximations of min-max control and continuous approximations of variable structure control. Assuming that the state-feedback controller robustly stabilizes the system in the presence of matched parametric uncertainties, we are to design the observer such that the observer-based control recovers the stability robustness of the state-feedback-control. We will show that it is possible to design such an observer, if the nominal, system is left-invertible and minimum-phase.