Fast Regulation Method for Commutation Shifts for Sensorless Brushless DC Motors

Sensorless brushless DC (BLDC) motor drive systems are often subjected to inaccurate commutation signals and can produce high current peaks and conduction consumption. To achieve accurate commutation, a fast commutation shift regulation method for sensorless BLDC motor drive systems considering the influence of the inductance freewheeling process is presented to compensate inaccurate commutation signals. The regulation method is effective in both steady speed and variable speed operations. In the proposed method, the commutation error is gained from the line-voltage difference integral in a 60 electrical-degree conduction period and the outgoing phase current before commutation. In addition, the detection precision of the commutation error is improved due to the consideration of the freewheeling period. The commutation error is directly obtained, which avoids successive optimization and accelerates the convergence rate of the proposed method. Moreover, the commutation error features a positive or negative sign, which can be utilized as an indicator of advanced or delayed commutation. Finally, experiments are conducted to validate the effectiveness and feasibility of the proposed method. The results obtained show that the proposed method can accurately regulate commutation signals.