Discrete-Time Position Tracking Control for Multimotor Driving Systems via Multipower Terminal Sliding-Mode Technique

With the popularization of computerized digital control systems, the discrete-time control design has attracted increasing attention. This article presents a novel discrete-time second-order multipower terminal sliding-mode control (DSMTSC) for the position tracking of multimotor driving servo systems. Instead of the traditional dynamic model, a discrete-time characteristic model, which possesses lower order and fewer parameters, is built based on the system input-output data. In the DSMTSC design, a multipower sliding function is constructed fitting different convergence stages, which achieves faster convergence rate and higher tracking precision than conventional terminal sliding functions. Furthermore, an improved reaching law is designed to avoid the integral saturation, and the high-order sliding-mode approach is utilized to reduce the chattering. The finite-step boundedness of both the sliding functions and the tracking error is proved by rigorous theoretical analysis. Comparative experiments are conducted on a four-motor driving servo turntable, and the results verify the advantages of the DSMTSC, which are particularly suitable for practical application.