Brushless DC Motor Without Position Sensor Speed Control Research Based On Predictive PI Method

Brushless DC motor uses power electronic devices instead of the traditional mechanical commutation means to overcome many drawbacks of the mechanical commutation means, and has as superior as DC motor speed performance, so it is widely used. At present, for brushless DC motors, hotspot research mainly focused on permanent magnet materials, control chip, without position sensor detection method, speed control method and torque ripple reduction. This paper mainly studied the without position sensor detection method and speed control methods of brushless DC motor to overcome the shortcomings of traditional without-position sensor detection and to further improve the effect of the brushless DC motor speed control.No position sensor detection method can save space inside the motor, and the advantage is very significant. However, the method based on voltage and current signals is widespread used now. That is, the rotor position is calculated through indirect detection through each phase voltage or current signal of brushless DC motor. This not only increases the hardware and wiring, and easily disturbances the system. Moreover, the issue of the motor start should to be considered. For this, this paper presents the method that direct taking use of brushless DC motor speed of control system to detect rotor position. The angular displacement as intermediate amount connects the rotor speed and the rotor position. This method not only detects high precision and overcomes the shortcomings of traditional methods.In the control method, because brushless DC motors are strongly coupled nonlinear systems, it is difficult to establish a precise mathematical model. Therefore, the effect of the classical PID control is not ideal. Intelligent control performance better, but its principle complex, computationally intensive, the static error large. Combined with intelligent and PID control, the parameters are difficult to set up. This paper proposes a predictive PI control method. That is, predict the next time motor speed according to the previous time and the current rotational speed, with it to direct current PI control. The multi-stage incremental speed forecast method was used to predictive speed. It overcomes many shortcomings of traditional control methods and can be set the appropriate order and prediction steps according to actual needs.According to brushless DC motor speed control system established based on the speed rotor position detection methods and predictive PI control method. By MATLAB simulation contrast, the advantages of high precision, stable operation of speed rotor position detection methods were verified. At the same time with the classic PID control and fuzzy control of contrast, the predictive PI control advantages of overshoot, settling time, overshoot, anti-disturbance and static errors were verified.