Adaptive quasi-sliding-mode tracking control for discrete uncertain input-output systems

In this paper, a discrete robust adaptive quasi-sliding-mode tracking controller is presented for input-output systems with unknown parameters, unmodeled dynamics, and bounded disturbances. The robust tracking controller is comprised of adaptive control and a sliding-mode-based control design. The bounded motion of the system around the sliding surface and the stability of the global system in the sense that all signals remain bounded are guaranteed. The adaptive algorithm, in which the deadzone method is employed even though the upper and lower bounds of the disturbances are unknown, is the extension of the authors' previous work for the state-space systems. An example and its simulation results are presented to illustrate the proposed approach.