New sliding surface design for a class of nonlinear sliding mode control systems

A new sliding surface design for sliding mode control of a class of nonlinear plants is proposed in this paper. The plants may involve the matched and unmatched uncertainties. In order to obtain the stable dynamics of the states with the unmatched uncertainties, the sliding surface that includes the unmatched uncertainties, whose values are assumed to be measurable, but structures are unknown, is constructed. The reaching phase is designed to ensure the stability of the closed loop with such a uncertain sliding surface. This result generalizes the robust design of the sliding mode control though the sliding surface may be uncertain.