Torque ripple suppression in non-commutation interval of the coreless brushless DC motor based on unipolar PWM predictive control

Abstract

Aiming at the torque ripple caused by significant current ripple and non-ideal back-electromotive force (back-EMF) of coreless brushless DC motor (BLDCM), an incremental predictive control strategy based on unipolar pulse width modulation (PWM) is proposed in the non-commutation interval. Firstly, the unipolar PWM scheme is used to double the current ripple frequency, which can reduce the current ripple. On this basis, the current prediction equations of adjacent control periods are subtracted to obtain the incremental current prediction equation, and the influence of non-ideal back-EMF on torque ripple suppression is eliminated. Finally, combined with the author's previous research on the commutation torque ripple suppression strategy, an integrated suppression strategy for non-commutation and commutation interval is proposed. The experimental results show that, compared with the PI control strategy, the total torque ripple of the proposed strategy is reduced to less than 35%, and the current ripple is reduced. Meanwhile, the commutation time is shortened, and the advantages of coreless motor rapid response are retained. The strategy is universal, not limited by motor parameters and operating conditions, and has theoretical and engineering value.