ABSTRACT
In the past few decades, sliding mode control (also known as variable structure control) has been extensively studied because of its advantage of strong robustness against model uncertainties, parameter variations and external disturbances. In sliding mode control, trajectories are forced to reach a sliding manifold in finite time and then stay on the manifold for all future time. It is worth mentioning that, in the existing literature concerning the sliding mode control (SMC) problem for nonlinear systems, the nonlinearities and uncertainties taken into consideration are mainly under matching conditions; that is to say, the nonlinear and uncertain terms enter the state equation at the same point as the control input and consequently the motion on the sliding manifold is independent of those matched terms. However, in engineering practice, a large part of external nonlinear disturbances and parameter uncertainties cannot be treated as a matched type of nonlinearities. In recent years, since most control strategies are implemented in a discrete-time setting (e.g., networked control systems), the SMC problem for discrete-time systems has gained considerable research interest and many results have been reported in the literature.
