Exactly detecting of rotor position was required during the control of brushless DC motor, and back EMF detecting method was a simple, effective way to detect the position-sensorless rotor position of brushless DC motor. A back EMF detecting method based on the H_PWM-L_PWM modulation model by analyzing the freewheeling condition of a non-conducted phase of this model was raised. This back EMF detecting method needed not to detect the center voltage of the three-phase winding, and gained a two times of the back EMF of a non-conducted phase. The simulation under MATLAB software environment and experimental results showed that this method had good performance in low speed control of brushless DC motor.%无刷电机的控制需要准确检测到转子的位置,反电动势法是检测无位置传感器无刷直流电机转子位置的一种简单、有效的方法.采用二相导通星形三相六状态的控制模式,通过分析在H_PWM-L PWM调制方式下不导通相的续流情况,提出了基于该调制方式的反电动势检测方法.该反电动势检测法不需要检测三相绕组中点电压,所获得的是不导通相的两倍的反电动势.MATLAB仿真和试验结果证明,该检测方法具有良好的低速控制性能.
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