The Research On Control System Of The Four-phase Permanent Magnet Brushless DC Motor

In recent years, as a new type of motor, permanent magnet brushless DC motor developed rapidly with the rapidly expand of the permanent magnetic materials, the electronic technology and the microelectronic technology. Because of the using of the electronic commutation to replacing the mechanical commutation, it has many merits, such as the good performance of the starting and speeding, the simple control method, the high reliability and the small environmental impact, which overcomes commutation sparks ills caused by the mechanical commutation of the general brush DC motor. It obtained the widespread application in many industrial fields such as in space, artificial intelligence robot, CNC machine tools, medical equipment, electric vehicles and many other industries.In order to detect the rotor position signal, the position sensor was attached to conventional brushless DC motor. which enhanced the cost and reduce the reliability of the motor, at the same time it enhanced the difficulty of the electrical machinery maintenance; Meanwhile the torque pulsation question existing in the movement process of the electrical motor greatly limited the application scope of the permanent magnet brushless DC. So the torque pulsation suppressing question and the non-position transducer control technology on the permanent magnet brushless DC motor have become a hot research at home and abroad. This paper will carry on the thorough analysis discussion about the torque pulsation suppressing question and the non-position transducer control technology on the permanent magnet brushless DC motor.This paper will focus on the following aspects to analysis and research the permanent magnet brushless DC motor control system:(1)This paper takes the four-phase permanent magnetism brushless DC motor as the example to analyze its work principle, build the electrical machinery mathematical model, use MATLAB/Simulink software to build system simulation model of the four-phase half bridge permanent magnet brushless DC motor.(2)The corresponding suppress method was proposed for brushless DC motor focusing on the different torque pulsation roots. After the analysis, the idea of the unideal counter electromotive force and the unideal current waveform as the primary cause created the brushless DC motor's torque pulsation was stated. This article mainly obtains from the control policy, through improving the counter electromotive force and the electric current profile to suppressing the electromagnetism torque pulsation in the phase change process. Overlap phase change law and the PWM pulse-duration modulation as the mainly methods were used and was confirmed effectively through the MATLAB simulation.(3)This paper describes several broader application non-position transducer rotor position signal detection methods of the permanent magnet brushless DC motor. By analyzing their basic principles, implementation methods, good and bad characteristics, finally this paper closes the most mature, most effective and most widely used "anti-EMF" complementing with "the three-stage" start method to achieve the four-phase brushless DC motor without position sensor detection technology. The simulation model was established in the MATLAB / Simulink software and the simulation results verify the rationality of the system.(4)The current and the speed double-loop structure was built in the simulation model, the current loop as the inner current loop used the hysteresis comparator control and the speed loop as the outer ring used the PI regulator control.