Introducing high-gain internal model to semi-global robust output regulation for minimum-phase nonlinear systems

We consider the assumption of existence of the general nonlinear internal model which is introduced in the design of robust output regulators for a class of minimum-phase nonlinear systems with rth degree (r ¿ 2). The robust output regulation problem can be converted into a robust stabilization problem of an augmented system consisting of the given plant and a high-gain nonlinear internal model, perfect reproducing the bounded including not only periodic but also nonperiodic exogenous signal from a nonlinear system which satisfies some general immersion assumption. The state feedback controller is designed to guarantee the asymptotic convergence of system errors to zero manifold. And the stabilization analysis of the resulting closed-loop systems lead to regional as well as semi-global robust output regulation achieved for some appointed initial condition in the state space, for all possible values of the uncertain parameter vector and the exogenous signal ranging over an arbitrary compact set.