Research And Implementation Of Brushless DC Motor Driver And Position Sensorless Control Technology

Brushless DC motor(BLDCM)has the advantages of high efficiency,large output torque,small size and good dynamic performance,making it widely used in the military industry,new energy electric vehicle industry,industrial automation and household appliances.In this paper,a750 W brushless DC motor is used as the research object,and a brushless DC motor driver with311 V DC bus voltage based on position sensorsless is designed.The driver hardware circuit of this project consists of: main circuit module,control module and auxiliary power supply module.In view of the problems of sensorless control in traditional BEMF(back electromotive force method),such as the phase lag caused by filtering circuit,the difficulty in detecting counter electromotive force at startup,and the influence of commutation continuous current at heavy load,This paper analyzes a sensorless control method for brushless DC motor using terminal voltage detection and comparison on non-conducting phase to conduct direct commutation.This method overcomes many defects of conventional BEMF,improves the accuracy of phase change,and realizes direct phase change of brushless DC motor position sensorless.The main content of this paper is as follows:(1)The working principle,mathematical model and corresponding knowledge are briefly explained,hereby the sensorless control method of brushless DC motor based on non-conducting terminal voltage detection is elaborated and the relationship and working characteristics on the startup between the non-conducting terminal voltage and the corresponding commutation point are analyzed.(2)The analysis of the main circuit module and control module of the brushless DC motor driver.The driving module hardware circuit comprises a three-phase inverter bridge circuit,an optocoupler isolation circuit and a driving circuit;the control module hardware circuit mainly comprises the STM32F103c8t6 minimum system circuit,resistance based current sampling circuit,speed input given circuit and terminal voltage detection circuit.(3)The analysis of auxiliary power module of the driver.The flyback converter is selected as the topology of the auxiliary power module and the design of the rectifier circuit,high-frequency transformer,voltage feedback circuit,absorption suppression circuit of auxiliary power module are completed,furthermore,the common problems of the auxiliary power module power supply during the debugging process are analyzed and solved.(4)The control system software programming is completed on the basis of the IAR development environment and the key technology of the system software implementation process is introduced in detail.Finally,build corresponding experimental platform.Through analyzing the power supply voltage waveform,drive waveform,commutation point contrast waveform,on-load velocity waveform and phase current waveform of the system,the reliability of the driver hardware circuit and the feasibility of the sensorless control method of brushless DC motor based on terminal voltage detection are verified.