Sensorless Control of Brushless DC Motor by Zero-crossing Back EMF Detection

According to brushless DC motor rotor position detection of positionless sensor control,this paper points out a rotor position detection method based on zero-crossing point back EMF,back EMF zero-crossing point signal is received via analysis and calculation of mathematical model of brushless DC motor and by comparison of the voltage difference detection between the floating phase terminal and the midpoint in DC bus.This method does not need the virtual midpoint of motor,low pass filtering circuit and voltage-dividing circuit but needs zero-crossing point back EMF signals in a specific PWM modulation mode and then delays 30 degree electric angle to implement commutation.MATLAB/SIMULINK simulation experiment results show that this method can reasonably and effectively detect rotor position and that this method has the advantages such as simple structure,wide application rage and so on by comparing with traditional back EMF zero-crossing virtual midpoint detection method.