Based on the mathematical model of the surface PMSM, a backstepping controller with sliding mode variable
structure is proposed. Sliding mode variable structure based on exponential reaching law enhances the quick response and
anti-disturbance ability of the control system. The integral action contained in the sliding surface can ensure the steady state
error of tracking velocity zero. At the same time, extended state observer is used to evaluate the load torque of the system
online, so the control process can be adjusted timely, which leads to the parameters of exponential reaching law being more
smaller. Theoretical analysis and Matlab simulation results show the effectiveness of the proposed method.