Mutual torque ripple suppression of surface-mounted permanent magnet synchronous motor

The mutual torque ripples generated by surface-mounted PMSM would degrade the motor performance at load condition. This paper gives a systematic way to suppress the mutual torque ripples using a MRAS-based flux linkage estimator and a LS-based harmonic selective filter. The mutual torque ripples are suppressed by modifying the motor current reference. A test fixture is specially designed to accurately measure the small torque ripples at high load torque condition. A verification test is conducted. The result shows good effectiveness of suppression control.

I. Introduction

Permanent Magnet Synchronous Motors (PMSMs) are often used in high demanding applications such as high performance servo drive, robotics, etc due to its high torque capabilities. High level of torque smoothness is normally required in many such applications. The torque ripples produced by the surface-mounted PMSM are normally classified into two categories: Cogging Torque Ripples and Mutual Torque Harmonics. The Cogging torque ripples are generated by the interaction of the rotor magnetic field and the angular variations in the stator magnetic reluctance which has been discussed in many publications. The mutual torque harmonics are resulting from the interaction of the stator current MMF and the harmonics of the rotor magnetic flux. Unlike the cogging torque ripples, the mutual torque harmonics appear only at load condition, so they are sometimes called additional torque ripples at load. The resultant motor torque ripples could get bigger when the load increases due to the existence of mutual torque harmonics. This phenomenon degrades servo performance especially at high load condition.