Commutation Error Correction Strategy for Sensorless Control of Brushless DC motor based on Back EMF

For sensorless control of brushless DC (BLDC) motor, the accuracy of commutation point identification has a vital impact on performance and load capacity. The relationship between terminal voltage waveform and deviation of commutation point is analyzed in the case of advanced or lagging commutation. The detection error of zero-crossing due to the voltage spike is analyzed. Therefore, a new commutation error correction strategy based on back-EMF is presented. By means of keeping the symmetry of the waveform of terminal voltage, the commutation point is corrected by controlling the delay angle of the zero-crossing signal in a closed loop. This strategy offers some useful benefits: 1) it doesn’t need non-essential extra hardware; 2) it ensures correctness and reliability of control strategy in a wide speed range. The above-mentioned method is verified experimentally on a 2-pair-pole BLDC motor.