Research On Control System Of Sensorless Brushless DC Motor

The brushless DC motor is widely used in industrial and commercial fields,based on advantages of simple structure,high operating efficiency and convenient maintenance.However,the position sensor of the brushless DC motor increases the cost of the motor and reduces the reliability of the system,and torque ripple reduces the performance and energy utilization of the motor.Therefore,this thesis studies and analyzes the sensorless technology and torque ripple suppression technology.Aiming at the problem of the traditional back-EMF zero-crossing detection method,the back-EMF amplitude is too small at low speed,and it is difficult to detect the rotor position,a hybrid voltage rotor position detection method is adopted under the bipolar modulation method.This method is based on the traditional back electromotive force method,combined with the line voltage difference method to jointly obtain rotor position information,according to the speed adaptive selection of the better method,making the brushless DC motor Stable rotor position detection from low speed to high speed.By building a sensorless brushless DC motor control system model for verification,the results show that the proposed method can make the motor work in a wider speed range,avoiding the difficulty of effectively detecting the back EMF in the low-speed region,and influence of high back-EMF on detection circuit in high-speed area without Distribution by PWM modulation.Aiming at the torque ripple generated during the commutation of the brushless DC motor,a current prediction control method is used to suppress it under the bipolar modulation mode.This method takes the phase current as the control target,and obtains the controller modulation duty cycle through the prediction model,so that the winding current of the turn-on phase and the turn-off phase during the commutation phase change rate is equal,and the non-commutation winding current remains constant.Thereby reducing the torque ripple caused by commutation.The simulation results show that the proposed method can eliminate the freewheeling of the diode on the cut-off phase and avoid the torque ripple caused by the freewheeling of the diode,and can be applied to the full speed range,with strong robustness and fast response speed.Based on the above research,an sensorless brushless DC motor control system based on ARM was designed,the hardware and software were designed and debugged,through the comparative analysis of the operating data of the control system through experiments,the feasibility and effectiveness of this control system are verified.