Rotor Position Detection for Brushless DC Motor Based on Line Voltage Difference

The primary problem of brushless DC motor control without position sensor is that six key rotor position signal can be detected for electronic commutation in each electric cycle.The back-EMF method is currently the most mature technology,the most effective and the most widely used method of rotor position detection.Based on back-EMF method principle one kind detection method based on the line voltage difference calculation was proposed.The rotor position was estimated through the calculation of two phase line voltage difference to get back-EMF zero-crossing point.The relationship between motor neutral voltage and half DC voltage was analyzed then the follow current situation of non conduction phase in different modulation was obtained.This method was compared with traditional back-EMF zero-crossing fictional neutral point detection method has the advantages of simple structure,no need to reconstruct motor neutral point and have higher sensitivity.Through the theoretical analysis and simulation results indicate that,the back-EMF method based on line voltage difference is easy to control and can effectively identify the rotor position.