Robust semi-global output tracking for nonlinear singularly perturbed systems

In this work, a robust controller design methodology for a broad class of singularly perturbed nonlinear systems with time-varying uncertainties is developed. When the fast subsystem is stabilizable and the slow subsystem is input/output linearizable with ISS inverse dynamics, the developed state feedback controller guarantees boundedness of the trajectories of the closed-loop system and robust output tracking with arbitrary degree of asymptotic attenuation of the effect of uncertainty on the output, for initial conditions, uncertainties and their derivatives, in an arbitrarily large compact set, as long as the singular perturbation parameter is sufficiently small. The controller is a continuous function of the state of the system and its construction requires the knowledge of bounding functions on the size of uncertainty.