Disturbance Compensation Sliding Mode Control for Discrete Systems with Unmatched Uncertainties

Aiming to the chattering problem on a class of discrete systems with unmatched uncertainties (DSUU), a sliding mode control (SMC) strategy is considered based on disturbance compensation reaching law in this paper. First, a novel reaching law with disturbance compensation via hyperbolic tangent function is proposed and the dynamic characteristics of sliding mode are analyzed. Then, a sliding mode controller with disturbance compensation is designed via the proposed reaching law and the linear sliding surface function. Furthermore, the reachability of quasi-sliding mode (QSM) is constructed in finite time and the stability of system dynamic trends is obtained by the proposed reaching law for DSUU. Through comparative analysis, the steady performance of system by new controller is better than those systems by traditional reaching laws and its QSM has a narrower bandwidth. Finally, simulation results illustrate that the proposed SMC strategy is feasible and effective.