Research And Design Of Sensorless BLDCM Control System

With the rapid development of electronic technology,brushless BLDCM is becoming more and more widespread,and is gradually replacing brushed motors in many fields,especially in the electric vehicle industry.In order to solve the problem that the hall sensor used in electric vehicles is easy to be damaged,this topic focuses on designing a brushless BLDCM control system without hall sensors in the electric vehicle industry.This project first demonstrates the method of positioning the rotor using the back-EMF zero-crossing detection method.This solution observes the back-EMF for rotor positioning and speed measurement.the back-EMF Undetectable problems have been designed with a three-stage start-up scheme.In addition,the subject discusses the principle of using fuzzy-control to complete parameter self-tuning based on the traditional PID algorithm.The hardware design includes the minimum system circuit,power supply circuit,drive circuit,back-EMF zero-crossing detection circuit,current detection and protection circuit,and other hardware circuits.The system is controlled by the main state machine on the software,and multiple software modules are independently designed for different functions performed by different states of the motor,including the start module,commutation module,speed detection module,speed control module,and wireless communication module.The module uses the fuzzy-PID algorithm to improve the speed control performance when designing the speed control software.This design selected the STM32 series microprocessor,and used the ESP8266 module to expand the system’s WiFi wireless communication function,designed the communication protocol between the upper computer and the lower computer,wrote the Android mobile phone APP,and realized the remote control of the mobile phone.The system can monitor the status of the motor in real time.The BLDCM control system developed in this paper has verified its three-stage start-up function without hall sensor through actual tests.The start-up time is controlled within 200ms to meet the needs of practical applications.The back-EMF zero-crossing detection method is adopted The rotor positioning is reliable and stable,and it performs well in the speed range of 200-3000 rpm;the fuzzy-PID control of the motor speed is achieved,and its performance is improved compared with the traditional PID control;the WiFi wireless communication of the control system expansion is stable.