Sensorless Brushless DC Motor Controller

With the wide use of DC motor in industrial manufacturing and living appliances,the traditional DC motor with sensor is more and more limited.So sensorless brushless DC motor came into being.Study of brushless motor in Sensorless DC,starting algorithm,rotor position detection and control algorithm is a research hotspot.Good starting performance,accurate position detection and good speed regulation are the control objectives of the sensorless brushless DC motor.As a result,it is necessary to develop an effective controller for Sensorless Brushless DC motor.Based on the analysis of the operation principle and mathematical model of the brushless DC motor,the theory back EMF zero crossing detection and circuit are studied in details.Then present a new method to detect the rotor position--AD sampling back EMF and a new startup algorithm--the closed loop start.This paper designed a contrast experiments.One group uses AD sampling BEMF position detection and closed-loop startup,which adopts PWM-OFF modulation method to replace the diode freewheeling.Another group uses the traditional back EMF zero crossing detection and three starts startup.Both of the experiments' hardware and software design have been finished.Since the back EMF in low speed is easy to be submerged in the continuous flow of the diode.The first group of experiments uses special modulation mode to suppress the influence of freewheeling diode and AD sampling back EMF is more accurate.As a result,the first group has better performance and stability.In this paper,we take a research on error and interference of the sensorless control of the brushless DC motor and propose the error compensation method and less interference.Finally,this system uses STM32F051 controller as the hardware platform of the sensorless control system for brushless DC motor and KEIL as the software integrated development environment.The experimental results show that the hardware and software platform of the system can well complete the control function of the sensorless brushless DC motor,and the platform has simple structure,good speed regulation performance and good stability.