Observer based sliding mode control of PMSM speed regulation system with a novel reaching law

A novel reaching law based sliding mode control of PMSM speed regulation system with uncertainties and unknown external disturbance is proposed in this paper. The proposed reaching law mainly consists of a time‐varying gain and a fractional power term of the sliding variable. And the time‐varying gain is auto‐tuned by the sliding variable such that it is large when the sliding variable is far away from the sliding surface to speed‐up the reaching process, and vice versa. Unlike the existing auto‐tuning power rate reaching law (PRRL), the proposed reaching law provides a guaranteed reaching time independently on initial conditions. Moreover, the reaching time can be effectively reduced by tuning the gains of the reaching law. Based on this new reaching law, a disturbance observer is designed to estimate the unknown total disturbance and a sliding mode controller is designed for the robust control of PMSM speed regulation system based on the estimated disturbance. Simulations and experiments are carried out to verify the effectiveness of the proposed control method.