Design and Analysis of a New Inverted-T Shape Permanent Magnet Servo Motor With Irregular Flux Barriers for Low Torque Ripple

Abstract

Permanent magnet (PM) motors should have ultralow torque ripple when used in robot joints with high positioning accuracy. For this reason, to decrease the torque ripple of the conventional inverted-T shape PM (ITSPM) motor, an irregular flux barrier (IFB) is designed on the top of the spoke PM, achieving an ultralow torque ripple. On this basis, a method that combines the qualitative analysis-area difference and the quantitative calculation-angle difference is proposed, demonstrating the design mechanism of lowering the torque ripple. More importantly, the proposed method applies to all motors. This proposed method consists of the following two steps: first, the main harmonics contributing to the torque ripples are analyzed to be the 13th and 35th harmonics based on the flux modulation theory; and then, the optimal parameter values of the IFBs that make these two harmonics the smallest are calculated using the principle of flux equivalence. In addition, the validity and feasibility of the proposed motor are verified by FEA and experimental tests.