Design of a novel speed controller for direct-drive permanent magnet synchronous motor based on reduced-order load torque observer

In order to reduce the speed overshoot of the traditional PI speed controller in direct drive permanent magnet synchronous motor(DD-PMSM), a novel speed controller is presented in this paper. In addition, a reduced-order load torque observer is proposed to reduce the effect of load torque changes and other disturbance factors on the system performances. The observed torque is imported to the input of q-axis current regulator, which is used as the signal compensating for the output reference current of the novel speed controller. Simulation and experimental results show that the speed overshoot can be reduced and the speed response could be improved by adopting the designed novel speed controller. It is also demonstrated that the capacity of anti-load torque disturbance can be improved significantly with the feed-forward compensation. Therefore, the validity and effectiveness of the proposed novel speed controller based on reduced order load torque observer are verified.