Abstract
In this paper, we study a robust adaptive output feedback tracking control for uncertain nonlinear systems violating existence of a well-defined relative degree. For this control scheme, the uncertain nonlinear systems are first remodeled into a class of approximate nonlinear models with parametric uncertainty and system uncertainty on some essential assumptions. Then, without causing no overparameterization of unknown parameters, a feedback nonlinear control law and a parameter update law are determined from an approximate linear model and a state observer system via approximate input-output feedback linearization with additional properties. By using this technique, it can be confirmed that both boundedness of all the states and adaptive output tracking objective of the closed-loop system are rendered.
