Sliding mode control for permanent-magnet synchronous motor based on a double closed-loop decoupling method

Permanent-magnet synchronous motor (PMSM) is a multivariable nonlinear system with strong coupling. In this paper, a new decoupling method is proposed for a double closed-loop system with the speed feedback in external loop and the current feedback in internal loop, in which the sampling time of external speed loop is much longer than that of internal current loop. When the calculation of the current loop is carried out using sliding mode control (SMC), the speed in external loop is made as a constant. In this case, the SMC controller is a multi-input multi-output system with variable coefficients. Compared with conventional PID control, the proposed approach demonstrates strong robustness against disturbance and has a rapid response.