Chattering-free and fast-response sliding mode controller

A new chattering-free and fast-response sliding-mode controller with a smooth control law (SMCS) is proposed. Unlike the conventional sliding-mode controller (SMC), or sliding-mode controller with boundary layer (SMCB), which obeys the variable-structure control principle by adopting a switching control term, the proposed SMCS uses a continuously varying term instead which takes the distance of the system state from the sliding surface into account. As a result, chattering is eliminated, and the control performance is improved in contrast to the popularly used SMCB in terms of system response, robustness, adaptability and maximum steady-state error. Both theoretical analysis and simulation studies have been carried out to verify the superiority of SMCS over SMCB. A step-by-step systematic design procedure for SMCS is presented and applied to speed control of a PMSM drive system.