Research On Sensorless Brushless DC Motor Control Technology

The role of the motor is to convert electric energy into mechanical energy through electromagnetic reaction.Its appearance accelerates the development of human society.At the same time,the rapid advancement of society and the rapid development of the motor have led to the emergence of a variety of motor types.Motor play an important role in various field.Among them,the brushless DC motor has become a star in contemporary motors because of its high conversion efficiency,low noise,small size,long service life and low maintenance cost.The appearance of the position sensorless brushless DC motor further improves the adaptability of the ordinary brushless DC motor and can meet the application requirements of special fields.It plays an important role in industrial automation,robotics,automobiles,etc.In future brushless DC motors will take up a large share of the motor marketThe research focus of this thesis is on the algorithm of detecting the rotor position and stable operation by the non-position sensor brushless DC motor through the back electromotive force zero-crossing comparison.By understanding the principle of the basic structure of the brushless DC motor and mathematical modeling,observe the characteristics of the change of the back electromotive force of the motor during operation,and determine how to use the back electromotive force zero-crossing comparison to detect the rotor position instead of the position sensor feedback rotor position.,allowing the motor to operate without a position sensor.Then introduce the simulation circuit diagram through the Simulink simulation platform in MATLAB,and check the running effect of the brushless DC motor using the back electromotive force zero-crossing comparison detection rotor position algorithm.By studying the three-stage starting method,the problem that the position-free sensor brushless DC motor has zero back-EM potential when it is at rest can not be activated.Introduced PID control to form a double closed loop system of brushless DC motor speed loop and current loop.Finally,with STM32F302R8 as the main control,the software and hardware of the double closed-loop control system of the position sensorless brushless DC motor are designed.The actual waveform diagram is analyzed to verify the reliability of the control algorithm and the stability of the double closed loop system.