A Fast Commutation Error Correction Method for Sensorless BLDC Motor Considering Rapidly Varying Rotor Speed

Accurate commutation point is essential to ensure the ideal torque performance and low power consumption for brushless DC (BLDC) motor. In order to achieve the precise sensorless commutation at a constant or the rapidly varying speed, a fast commutation error correction method is proposed in this article. First, it is pointed out that the controlled variable variation, the high rate of commutation error relative to the low speed and the nonlinearity of the correction loop are the main origins of commutation error when the speed varies rapidly. Then, a novel commutation error correction method is proposed through the following three aspects: first, constructing a controlled variable first utilized for commutation correction, which keeps constant at the rapidly varying speed; second, incorporating feedforward compensation for the phase shift caused by low-pass filter; third, using feedback linearization to reduce the nonlinearity of the correction loop. The proposed commutation error correction method not only corrects the commutation error fast at a constant speed, but also achieves precise commutation when the rotor speed changes rapidly. Moreover, the proposed method is based on the principle of closed-loop control, thus, it also has the advantage of anti-interference. At last, the experimental results are shown to validate the effectiveness of the proposed method.