| This dissertation addresses some important control problems including stabilization, tracking and output regulation for uncertain nonlinear systems, with focus on the global output regulation.; First, we study the partial-state feedback stabilization problem of cascade systems using a nonlinear small gain theorem. We point out that input-to-state-stability (ISS) of zero dynamics with a locally Lipschitz continuous gain function suffices to guarantee the existence of globally stabilizing, smooth partial state feedback control laws for cascade systems. In the second part we show how the adaptive control method developed recently for nonlinearly parameterized systems can be used to solve the problem of global output regulation. For nonlinear systems in the so-called output-feedback form, we achieve the global output regulation without knowing the bounds of parameters and exogenous signals. In this part, tracking problem via output feedback is also solved for a class of nonlinear systems bounded by linear growth condition. In the last part, a time-varying partial-state feedback design approach is proposed for global output regulation of cascade systems with non-polynomial nonlinearity. We show how an adaptive time-varying nonlinear internal model can be designed to achieve the global output regulation without the knowledge of the bounds of exosignals and unknown parameters a priori. We also discuss how the common condition that the exosystem is neutrally stable can be relaxed, so that output regulation of unbounded reference signals is possible. |
