Three phase brushless DC motor has the characteristics of high power density, simple structure and excellent speed regulation performance, which is widely used in the field of electric drive. Open-end winding brushless DC motor has no neutral point, and each phase winding is electrically isolated, which can realize the independent control of each phase winding. Compared with Y-connected brushless DC motor, the open-end winding brushless DC motor has a wider range of speed regulation under the same voltage, and has certain fault-tolerant performance, which is suitable for the application of low voltage and large current. Compared with the multiphase fault-tolerant motor, open-end winding brushless DC motor has simpler structure and higher winding utilization rate. However, the open-end winding brushless DC motor still has torque ripple, among which the cogging torque is related to the motor body structure, while commutation torque ripple is affected by the mutual inductance of the winding and the current freewheeling loop. The commutation process of the open-winding brushless DC motor is analyzed, and it is concluded that the current change rates of the turn-off phase and turn-on phase are equal under the ideal back electromotive force(back-EMF), which can ensure that the non-commutation phase current and the electromagnetic torque kept constant. The overlapping commutation with phase current closed-loop method is proposed to suppress the commutation torque ripple of open-end winding BLDC motor, and the applied voltage on turn-off phase and delayed time of turn-off phase in overlapping commutation are derived, the sliding mode observer is used to calculate the electromagnetic torque. MATLAB simulation and experimental results verify the effectiveness of this method.

三相无刷直流电机具有功率密度高、结构简单、调速性能优良等特点，广泛应用于电力驱动领域。开端绕组无刷直流电机无中性点，各相绕组电气隔离，可实现各相绕组独立控制。与Y接无刷直流电机相比，开端绕组无刷直流电机在相同电压下的调速范围更广，并具有一定的容错性能，适用于低压大电流的应用。与多相容错电机相比，开端绕组无刷直流电机结构更简单，绕组利用率更高。然而，开端绕组无刷直流电机仍然存在转矩脉动，其中齿槽转矩与电机本体结构有关，换向转矩脉动受绕组互感和电流续流环的影响。对开式绕组无刷直流电机的换向过程进行了分析，得出在理想反电动势(back-EMF)下关断相和导通相电流变化率相等的结论。确保非换相相电流和电磁转矩保持恒定。提出了相电流闭环重叠换相方法来抑制开端绕组BLDC电机的换向转矩脉动，并推导出重叠换相时关断相的外加电压和关断相的延迟时间，滑模观测器用于计算电磁转矩。MATLAB仿真和实验结果验证了该方法的有效性。