ASYMPTOTIC REGULATION OF MINIMUM-PHASE NONLINEAR-SYSTEMS USING OUTPUT-FEEDBACK

We consider a single-input/single-output (SISO) nonlinear system which has a well-defined normal form with asymptotically stable zero dynami cs, We allow the system's equation to depend on constant uncertain par ameters and disturbance inputs which do not change the relative degree , Our goal is to design an output feedback controller which regulates the output to a constant reference, The integral of the regulation err or is augmented to the system equation, and a robust output feedback c ontroller is designed to bring the state of the closed-loop system to a positively invariant set, Once inside this set, the trajectories app roach a unique equilibrium point at which the regulation error is zero , We give regional as well as semiglobal results.