Funnel Transformation Function-Based Discrete-Time Sliding-Mode Control with Reaching Law for Servo Systems

This paper proposes a funnel transformation function-based discrete-time sliding-mode control with reaching law for the discrete-time servo systems with unknown frictions and disturbances. Taking into account the unknown parameters of the system model and friction model, a recursive least square algorithm is designed to estimate the unknown parameter vector. Based on the identified system model, a novel discrete-time sliding-mode control is proposed to constrain the tracking error within a predefined funnel region and address overlarge initial control inputs in equivalent control-based discrete-time slidingmode control. The stability of the closed-loop system has been theoretically verified, and experimental results have further illustrated the effectiveness of the proposed method.