A Current Index Approach to Compensate Commutation Phase Error for Sensorless Brushless DC Motors with Nonideal Back EMF

Commutation phase errors during implementation are inevitable in the sensorless drive of the brushless dc (BLDC) motor. This paper analyzed the current waveform during the conducting phase under commutation phase error and nonideal back electromotive force (EMF). The relation between the elapsed time of the commutation phase error with the current waveform, the supplied voltage, and the nonideal back-EMF is derived. Based on this relationship, a reliable optimization method for commutation phase errors compensation is presented. Such method is to minimize the elapsed time of the commutation phase error with robustness properties with respect to parameter variations. In such a way, the peak values of the current at the front and back of the current waveform at each conducting period become more identical, which leads to minimum torque ripple. A digital signal processor-based sensorless BLDC motor controller to implement the proposed method is developed to verify its effectiveness experimentally. Experiment results showed that the proposed sensorless drive is capable of running in different speed and load torque with good performance.