Nonlinear Output Regulation: Robust and Adaptive Approach

Output regulation is one of the most fundamental control problems and it aims to design a feedback controller to achieve asymptotic tracking and disturbance rejection in an uncertain plant. It distinguishes from other problems/approaches in that it can handle a class of reference inputs and disturbances generated by an autonomous system called exosystem. The key technique in handling the output regulation is the Internal Model Principle which was originated in the 1970s when the linear robust output regulation problem was studied. This talk will focus on the output regulation problem of nonlinear systems. The key for tackling the nonlinear output regulation problem relies on a full extension of the concept of the internal model from linear domain to nonlinear domain. Such extension took place in early 1990s and has been in a process of constant evolving. In this talk will first characterize the internal model in such a way that it is a dynamic compensator that together with the original plant constitutes an augmented system with the property that the stabilizability of the augmented system implies the solvability of the output regulation of the original plant. Then we further proceed to the concept of the adaptive internal model which arises from handling the output regulation problem of nonlinear systems subject to uncertain exosystems.