Modeling And Simulation Of Brushless DC Motor Without Rotor Position Sensor

Brushless DC Motor(BLDCM) has been used widely in many fields such as aerospace, electromobile,medical machine and household appliances etc.The traditional BLDCM gets the changing phase signals to control the speed by assembling position sensors.But it also brings some disadvantages such as too much circuits,size control, high cost and so on.Thus the sensorless control is proposed.The control circuit structure is complicated because Traditional back-EMF zero-crossing detection needs delay circuit and filter circuit.Based on the mathematical model,the paper explains the operation characteristics and control modes.A novel Back-EMF zero-crossing detecting method solving the problems of the traditional BLDCM is planed to avoid the interference of the high frequency noise and gets rid of the generator neutral point and the filter.In addition,the modeling and simulation of the control system of BLDCM based on MATLAB/SIMULINK is a main reserch method. Aiming at the problems which the existing modeling methods have the complex modeling process,a large number of calculation and slow simulating speed,a novel modeling method of the phisical connection according to the electric principle structure of BLDCM is established.It contains inverter, the principle of brushless DC motor,rotor position detector,changing phase logic decoder and pulse width modulator.The simulation results show that the new way is simple and deirect to wiew.The new model also can be used as a standard library for it is convenient to change parameters or update the control systems.More importantly, this pape analysed the reason of BLDCM’s torque fluctuation in detail and set up single close loop PWM speed control system,digital PID control system and fuzzy PID intelligence control system.The results of control systems show that each system’s advantage and disadvantage in controlling of speed and torque,and also prove the model of BLDCM is useful.