An Improved Low Speed Control Strategy for Permanent Magnet Synchronous Motor with Low Resolution Encoder

In this paper, a composite speed control strategy is proposed to achieve a smooth speed response for the PMSM which is running at the low-speed range with a low encoder resolution. Under these preconditions, the encoder pulses may not exist in each sampling period. Therefore, there is a large lagging between instantaneous speed and measured speed. An extended state observer is designed to estimate the instantaneous speed. To improve the anti-disturbance ability and get a stable speed performance, a generalized model predictive speed control was applied. Based on the predict speed, a cost function is designed, and the q-axis is derived through minimizing the cost function. Considering the dead-time effect under low current amplitude, the parasitic capacitance cannot be ignored. Therefore, a voltage compensation model is re-established in this paper. The proposed control algorithm is verified through simulation and experimental results.