Fast Self-Correction Commutation Method for High-Speed Sensorless BLDCMs With Nonideal Asymmetric Back EMF

As a space application, the brushless dc motor (BLDCM) configured in a magnetically suspended control moment gyroscope has extremely high requirements for reliability and power consumption, where accurate commutation control is the key point. However, inevitable nonideal factors, especially the nonideal asymmetric back-electromotive force (back EMF) characteristics, would dramatically reduce commutation accuracy. In order to meet the requirements, this article proposes a fast self-correction commutation method for the sensorless BLDCMs with nonideal asymmetric back EMF. First, it analyzes the influence of nonideal asymmetrical back EMF characteristics on commutation accuracy and obtains the commutation point through the zero-crossing points of line-to-line voltages. Second, a novel phase shifter is proposed for the commutation error correction based on the amplitude transformation of back EMF. Finally, based on the relationship between the voltage difference and the commutation error, a closed-loop voltage adjuster with feedforward compensation is proposed to correct the commutation error using the phase shifter. Both simulation and experimental results validated the effectiveness of the proposed method.