Low-Speed Performance Improvement of Permanent Magnet Synchronous Motor Drive Based on Nonlinear Disturbance Torque Observer

When the permanent magnet synchronous motor runs at low speed, the fluctuation of cogging torque and the influence of friction force will cause the change of load torque. With the error and delay of speed detection, the dynamic performance of the system is reduced and the speed of the motor fluctuates. In this paper, a nonlinear disturbance torque observer is used to observe the load torque. In the q-axis current loop which is controlled by field-oriented vector control, the observed load torque is feedforward to the current loop as to suppress the speed fluctuation caused by the disturbance torque. The non-linear disturbance torque observer does not need the second derivative of the position, which reduces the measurement noise disturbance of the system. At the same time, the inertia of the motor parameters in the observer is identified. The simulation and experimental results show that the nonlinear disturbance torque observer has good suppression performance for the velocity fluctuation running at low speed.