Study of speed control algorithm in four phase BLDC vehicle cooling fan controller

This paper presents a speed control algorithm of the vehicle cooling fan driven by four phase bifilar winding brushless direct current motor (BLDCM). The related algorithms including rotor position detection of the four-phase BLDCM, speed update and field weakening control are described and analyzed in detail. In the design sensorless BEMF zero-crossing detection algorithm is used to realize the correct commutation so that the speed of the motor can be controlled. At the low or intermediate speed, combined with the related parameters gained from repeated experiments, the commutation period algorithm is produced. At the high speed, the motor takes advantage of conduction angle extending algorithm to increase the speed with the help of field weakening effects. All the algorithms mentioned in this paper have been proved in the vehicle cooling fan controller system based on the four phase bifilar winding BLDCM.