Brushless Dc Motor Dsp-based Digital Control System

The thesis first expounds the basic component parts, the basic running principle, the running characteristic and transfer function of the Brushless DC Motor(BLDCM). The knowledge on DSP is also simply introduced and the TMS320F240 DSP controller is paid more attention. Then the thesis detailedly dissertates its research pivot: the software realization of sensorless commutation detection based on the method of back electromotive force(Bemf) and open-loop commutation start-up. In this chapter, the method of BLDCM rotor position detection is first discussed. Then the principle and algorithm of Bemf zero crossing point detection is explained. In succession, the chapter dissertates the software realization of the Bemf zero crossing point detection algorithm, the software disturbance filter and the modification of phase displacement, and the software realization of commutation point. Finally, the chapter dissertates the strategy of software open-loop commutation start-up. In the following two chapters, the hardware and software design of the digital control system is dissertated in detail. The chapter of hardware design first expounds the whole design. Then the design of several primary circuits is discussed and the choice of some important electronic components and their parameters in these circuits is analysed emphatically. The chapter of software design also first expounds the whole design. Then some problems on software realization are dissertated. These methods of software realization are the significant embodiment and application of the "software in place of hardware" design thought which is proposed in this thesis. Next a few primary sub routines are expatiated. At last, the whole control strategy of the digital system is presented. After we apply the design scheme of the thesis to a Brushless DC motor, the experimental results indicate that the digital control system based on TMS320F240 DSP chip can make the motor start successfully. The time of startup is less than 3 seconds. And what's more, the digital control system realizes the motor's correct commutation and smooth running. Compared with a pure hardware BLDCM controller, the terminal voltage waveform corresponding to the control system designed in this thesis is smoother and its control effect is even better than that of the pure hardware control system.