Robust Adaptive Tracking by Measurement Feedback for a Class of Nonlinear Systems

Abstract

We address the tracking or regulation problem for a class of nonlinear systems with uncertain constant parameters and unknown timevarying disturbances, when the variable to be controlled is allowed to be different than the measured variable. The goal is to achieve asymptotic tracking or regulation when disturbances are zero and to guarantee bounded closed loop signals in any case. The class of systems are assumed to be transformable into an observable form with nonlinearities depending only on the measured variable, and are minimum phase with respect to the measured output. Under additional restrictions on the vector field multiplying the uncertain parameter (which vanish when the variable to be controlled is measured) we show how to solve the posed regulation problem for nonmimimum phase systems and the tracking problem for minimum phase ones (with respect to the variable to be controlled).