Abstract: In view of the problem that the commutation error of brushless DC motor is difficult to accurately

measure during variable speed operation，the relationship between the integral of line voltage difference and the

motor rotation angle was analyzed，and it was proved that the integral value of the line voltage difference is a fixed

value at the accurate commutation point of the motor under different working conditions. Based on this，a precise

sensorless commutation control strategy for brushless DC motor was proposed. In addition，in order to reduce the

waveform distortion and ensure the accuracy of the integral value，a finite impulse response（FIR）filter with group

delay characteristics was designed. The simulation and experimental results show that the line voltage difference

integral can accurately reflect the commutation error of the motor，and the proposed strategy has good commutation accuracy during variable speed operation.

      Key words: line voltage difference integral；commutation error correction；finite impulse response（FIR）filter；brushless DC motor