Dynamic output feedback sliding mode control for nonlinear systems with mismatched uncertainty

In this paper, the robust stabilization problem for a class of nonlinear uncertain systems is studied using sliding mode techniques. Matched and mismatched uncertainties are both considered. By employing the sliding surface proposed by Zak and Hui [7], the stability of the sliding mode is shown first. Then, an asymptotic observer is established to estimate the system state variables based on a constrained Lyapunov equation, and a variable structure controller is proposed to stabilize the system by exploiting the estimated state and system output. The two major limitations of [7] are eliminated. Finally a numerical example is presented to show the approach in detail.