Simultaneous Load Disturbance Estimation and Speed Control for Permanent Magnet Synchronous Motors in Full Speed Range

Permanent magnet synchronous motors (PMSM), which are with the advantages of high torque-to-weight ratio and high efficiency, are widely applied in modern industrial systems. However, existing approaches may fail to accurately track the speed trajectory because of the load disturbances. This paper proposes an equivalent and combined control strategy to mitigate the slow time-varying load disturbances and decrease the overshoot for PMSM in full speed range. First, a state observer is proposed to reconstruct the current variables and speed state in the d-q axis. Hence, one can get the speed and position information without the sensors. Then, the disturbance and the load are estimated by the estimating law. Thus, it can reduce the effect of load and disturbances. Further, the PD control is introduced to weaken the overshoot. As a result, the speed trajectory can be more effectively hold both in high speed and low speed. Finally, numerical examples are presented to demonstrate the validity and effectiveness of the proposed estimation scheme and its robustness under different conditions.