Brushless DC Motor Control System Based On PIC Research

Brushless DC motor with the characteristic of electronic commutation, overcomes the disadvantages of Brushless DC motor with mechanical wear, complicated structure, difficult maintenance, etc. Brushless DC motor widely applied to the high speed performance of CNC machine tools, robots, household appliances, office automation equipments and other fields.The traditional brushless DC motor using Holzer mechanical sensor is used to obtain the rotor position,large volume and high cost,which has some limitations. In recent years, sensorless brushless DC motor has become the focus of researches.In this thesis, the sensorless brushless DC motor control system is studied. The structure and operation mode of Brushless DC motor are analyzed. On this basis, the rotor position detection method of the sensorless brushless DC motor is introduced in detail, including the back EMF zero crossing detection method, the three harmonic detection and so on. Because of the particularity of no position sensor,the three stage mode is selected. The mathematical model of Brushless DC motor is built. On the basis of the traditional PI control, the algorithm is optimized by using neuron adaptive PID and fuzzy variable coefficient PID, and the feasibility of the algorithm is verified by the simulation results. Choosing dsPIC30F4011 as the control core to build the hardware circuit and two sets of double closed loop control schemes are proposed. By contrast, MOSFET is selected as the inverter switching element. A new method for improving the measurement of back EMF is proposed, which does not require 30 degree detection.Through the MATLAB/Simulink simulation and experimental platform, the control system has good control effect and strong practicability.