| Brushless DC motor (BLDCM) is a new type of motor which is developed due to the development of the power electronics, control theory and motor control technology.BLDCM has been widely used in industrial applications because this motor not only has the merit of the AC induction motor for simple structure, reliable operation and easy maintenance but also has the merit of the DC motor for high performance and easy control. The brushless DC motor without using position sensors can reduce the extra cost and system size, and it also can enhance the reliability of the system.On the basis of the summary for developments and applications of brushless DC motor control system, the thesis introduces the structure and operational principle of BLDCM, then presents the mathematical models, and discusses the method of BLDCM rotor position detection which test the Back-EMF signal.Besides these the circuitry design of detecting rotor position is also presented in this thesis.In this thesis, the hardware and software design of the digital control system is dissertated in detail. The controller of the hardware of the system is built by using the TMS320LF2407 as the microprocessor. The design of detail circuit includes: the Back-EMF signal detection circuit, current detection circuit, rotor position and speed detection circuit. Besides, the drive circuit of the brushless DC motor is designed with IR2130.The software of the system includes: initialization program of DSP, open-loop commutation start-up program, the phase switching program and so on. Those programs achieve that the PWM generating, the open-loop commutation start-up, the phase switching, the control of current, speed, position.Finally, the thesis presents the simulation model of a BLDCM control system by using MATLAB/SIMULNK. By the model, the electromagnetic torque, rotate speed and back electromotive force cures are presented. The simulation results testify validity of the Back-EMF detection and prove the rationality of the control system.
|
PDF Full Text Request