Abstract: Brushless DC motor has been widely used in the market because of its long life，high reliability and

high torque. The sensorless control method can avoid a series of problems caused by the position sensor and further

expand the application of the brushless DC motor. Compared with the traditional sensorless control methods such as

the back-EMF method，the state observer method and the intelligent control method have better control performance，but they also need a lot of calculation. With the breakthrough of computer technology，these methods have also received more attention. The development of traditional sensorless control methods，state observer methods and intelligent control methods in recent years were analyzed and summarized，and several common starting methods were briefly introduced.

      Key words: brushless DC motor；position sensorless；back-EMF method；state observer；intelligent control