Automatic Optimization Method of Commutation for Position Sensorless Brushless DC Motor Based on DC-link Voltage

High-precision commutation is an important factor to ensure the high-efficiency operation and smooth torque performance of the brushless DC motor (BLDCM). In order to implement the position sensorless commutation, the commutation error is inevitably introduced from hardware and software implementation. To eliminate the commutation error, a automatic optimization method of commutation based on the DC-link voltage is proposed in this paper. First, the relationship between the commutation position and the voltage deviation of the DC-link voltage sampled before and after the commutation point is analyzed. Then, using the voltage deviation as the feedback quantity, a closed-loop controller is established to compensate the commutation point. Along with the voltage deviation converging to zero, a high-precision commutation is automatically reached. Therefore, the motor efficiency and output torque is optimized. Finally, the verification of the method is given by a magnetically suspended flywheel.