Robust controller design for a class of nonlinear systems with mismatched uncertainties

The problem of robust stabilization for a class of mismatched uncertain nonlinear systems is considered. The required information about uncertainties in the system is merely that the uncertainties are bounded in a Euclidean norm by a known function of the system states. It can be viewed as an extension of the work in Qu (1994). First, the uncertainties are decomposed into matched and mismatched parts. Then based on a Lyapunov method, a robust controller is proposed, which will compensate matched and mismatched uncertainties respectively. In contrast with some previous controllers which can only guarantee practical stability of the systems, the robust controller presented in the paper can guarantee that the resulting closed-loop systems are globally asymptotically stable. The simulation result shows that the method suggested is effective.