Load torque observer based sliding mode control method for permanent magnet synchronous motor

Considering the control performance requirements of high-performance printing press, a sliding-mode speed controller with torque feed-forward compensation is proposed in this paper. First, a sliding mode control method is presented for the permanent magnet synchronous motor(PMSM) of the printing press. Then, in order to reduces chattering phenomenon caused by system parameter variations and external time-varying load torque disturbances, by using a cascade observer design technique based on the sliding mode control, a load torque observer and a load torque derivatives observer are designed respectively. Since the estimated load torque and its derivatives are considered as the feed-forward compensation part to compensate sliding mode speed controller, the sliding mode controller may take a smaller gain for switching functions without sacrificing load disturbance rejection performance. The stability of the proposed scheme is verified using the Lyapunov method to determine the observer gain. The simulation result shows that the observer-based control scheme can decrease the chattering phenomenon effectively and improve control performance of PMSM remarkably.