Research on the Strategy of BLDC Motor Control Without Rotor Position Sensor

　　Research on the Strategy of BLDC Motor Control Without Rotor Position Sensor
　　A brushless DC motor(BLDCM), though an ac motor, has comparable performance as that of a dc motor, due to such advantages as simple construction, ruggedness, small size, and maintenance free. To control the speed of a BLDCM, hall sensors are usually used for speed sensing and position sensing. However, it would be more economical, if position sensors can be removed from the motor. Thus, this thesis proposes the sensorless control techniques for BLDCMs.This paper describes the operation characteristics and control strategies based on the mathematic neodymium standard state model of BLDC motors. A novel BEMF zero detection method is proposed to avoid the distribution of the high-frequency noise, get rid of the generator neutral point and the filter, solving the problem that exist in the traditional method. And against the difficulty that exist when the motor get started, there are two methods proposed: pre-locating method and zero crossing assisting method. The comparison can prove the validity of the pre-locating method, there’s no reverse rotation and speed fluctuations is small. The torque ripple is a problem needed to be solved too. Against the problem, the reason that cause the ripple is analyzed, and proves the PI controller, realizes the suppressing of the ripple. Here also discuss the speed estimating, too. In this paper the first level method is used to get the accurate speed of the rotor.The http://www.999magnet.com/products/112-neodymium-standard-state strategy above is used to design the BLDCM control system, and it’s studied deeply under the environment of SIMULINK. According to the result of the simulation, it is proved that the designed system is steady and the torque ripple resulting from commutation is limited somehow etc. So the system that studied is feasible.