Research On Control Method Of Speed ​​Control System Of Brushless DC Motor

Brushless DC motor using electronic commutation to replace the mechanical commutation, can avoid the questions of commutation spark caused by mechanical commutation of traditional DC motor. And Brushless DC motor is widely used in many industrial production and daily life due to the advantages of its large torque, high efficiency, small volume, wide speed range, simple structure, reliable operation, easy maintenance and no rotor losses, etc.Brushless DC motor is commutation controlled by detecting the position of the rotor. Position sensor detection is a traditional detection method. The sensor will increase the size and cost of the motor, and will reduce the reliability of the motor running, so sensorless control method becomes a research hotspot of brushless DC motor control. Sensorless control method of brushless DC motor is used in this paper, and position detection, motor starters and control strategies are the main research.Firstly, the research background and the domestic and foreign research status of the paper are introduced. Mathematical model is built according to the operation principle of a brushless DC motor.Secondly, to discuss sensorless control based on back EMF zero-crossing detection method. Traditional back EMF zero-crossing hardware detection method need to regard the reconstruct motor midpoint as the virtual motor midpoint, but the virtual motor midpoint is not equal to the actual motor point in many practical cases. So a better method called Line Back EMF detection method is used to detect rotor’s position. This method does not need to construct the virtual motor midpoint and can be used to estimate position for any flat top width of trapezoid wave, that has the advantages of simplicity and reliability. PI control is used for speed control of the traditional motor. The PI parameters depend on the mathematical model of motor, so system control performance will be affected when the motor parameters change in the operation process. The fuzzy control has the advantages of fast regulation speed and strong adaptability, due to its accurate mathematical model that does not rely on controlled object. This paper combines PI control and fuzzy control strategy, and fuzzy PI self-tuning control strategy is used for motor speed adjustment, so as to improve the robustness of motor speed control.Finally, the experimental platform is set up, hardware circuit and software design were included. Simulation model is established under MATLAB/Simulink software. The results of experiment and simulation are got and the method used in this article is proved to be correct.