High stabilization control of sensorless brushless DC motor on high speed

In the absence of position sensor, the brushless DC motor controller often used back electromotive force (EMF) zero crossing detection method to obtain the rotor position and speed during operation. Back EMF detection circuit noise and interference introduced by the PWM signal will affect the Back EMF zero-crossing detection signal, resulting in fluctuations and drift, using conventional MT solution method to extract rotor speed information can not effectively filter out interfering signals, and achieve high stability speed control. To improve speed stability control performance, accurate information to extract the rotor speed is needed as the feedback of controller. This paper designed a second-order state observer based on the speed of detection, compared with the conventional speed demodulation algorithm can effectively filter the back EMF zero-crossing signal interference, and accurately extract the rotor speed information. Experimental results show that the speed detection using this method, can achieve high stability control of motor speed.