Efficiency Improvement of a Double-Stator Permanent Magnet Vernier Machine for Direct-Drive Robotics

Abstract

This paper proposes an efficiency improvement operation of a new double-stator permanent magnet vernier (DS-PMV) machine for direct-drive robotics. The high torque density, low power loss and low torque ripple are expected for the direct-drive machines in robotic application. First, the staggered-teeth and electric offset (ST-EO) modulations are artfully incorporated for the torque density improvement and torque ripple reduction. By this mean, the average torque increases from 27.1 Nm to 43.2 Nm, and torque ripple decreases from 21.7% to 3.5%. Second, the model predictive torque control (MPTC) with maximum torque per ampere (MTPA) operation is integrated for fast dynamic response and power loss reduction. In this way, under the rated load condition, the armature current decreases by 20% and the copper loss reduces by 36%. Also, the efficiency of the proposed DS-PMV machine is up to 86%, which can be a preferred alternative for the direct-drive robotic application. Finally, the demonstration is performed to verify the validation of the proposed high-efficiency DS-PMV machine.