Suppression technique for torque ripple of brushless DC motor caused by PWM mode switching

In view of the current variation characteristics of brushless DC motors under different modes of PWM, it is necessary to select an appropriate PWM mode under different power assistance conditions to improve the smoothness in the process of power assistance and the returnability of EPS system. A scheme of maintaining the average current slope constant proposed in this paper effectively suppresses the torque ripple caused by the switching of PWM modes. In addition, current variation tendency remaining consistent before and after switching is also conducive to the swift tracking of assistance current, enhancing the response speed of system. The results of simulation and tests verify the effectiveness of the scheme.