High order sliding mode control for a PMSM with disturbance torque estimation

Disturbance torque estimation is crucial to the performance of a permanent magnet synchronous motor (PMSM). In this paper, a high order sliding mode (HOSM) controller with a differentiator is utilized for the first time for estimating the disturbance torque. Such a controller can eliminate chattering existing in a standard sliding mode controller. We first analyzed the nonlinear model of the motor, and derived the expression of its torque. Then we estimated the unknown uncertain disturbance torque, and input the estimated torque to the system. In this way, the system is improved. The result of simulation indicates that the disturbance torque has been estimated online successfully. In addition, the angle position tracking error of the nonlinear PMSM is less than 0.12rad.