Sensorless commutation deviation correction of brushless DC motor with three-phase asymmetric back-EMF

In view of the sensorless commutation deviation of brushless dc motor with asymmetric three-phase back electromotive force (EMF), this article presents a correction method of commutation deviation based on the principle of current consistency before and after commutation to achieve optimal commutation. First, this article analyzes the different factors resulting in the commutation deviation of the motor with asymmetric three-phase back-EMF, and then points out the deviation disadvantage. Based on the analysis, a commutation deviation correction method based on current consistency in ideal optimal commutation is proposed. At the same time, in order to eliminate the influence of waveform distortion caused by winding inductance in the commutation process, dc-link current reconstructor is proposed. Based on the reconstructed current value after commutation, an optimal commutation phase estimator based on commutation current consistency is designed to estimate the position of each commutation point. Finally, experimental results confirm that the proposed method can achieve high-precision deviation correction and optimal commutation at each commutation point in the case of asymmetric three-phase back-EMF.