The Research On The Control Of BrushLess Direct Current Motor Based On Back-EMF

The thesis first probably explains BrushLess Direct Current Motor (BLDCM), and discusses the related control methods, explains the background and Meaning of back electromotive force(Back-EMF) which is used in the thesis.Then the thesis expounds the basic component parts,the basic running principle,the running characteristic and transfer function of the BLDCM.And then the thesis detailedly dissertates its research pivot: the simulation of BLDCM system in MATLAB based on the method of Back-EMF and the control system of Digital Signal Processor(DSP) based on the method of Back-EMF.About the simulation of BLDCM system,Based on the mathematical model of BLDCM, a novel method for modeling and simulation of BLDCM system in Matlab has been proposed. In Matlab/Simulink, the isolated functional blocks, such as BLDCM block, Hysteresis current controller block, Speed controller block, ect., have been modeled. By the organic combination of these blocks, the model of BLDCM can be established easily. To guarantee the validity and speediness insimulation, the back- EMF is generated using piecewise linear curves. In the double loop of control system, a PI controller is adopted in the speed loop and a hysteresis current controller is adopted in the current loop. The simulation results testify the reasonability and validity of the Back-EMF,and also testify the validity of the method for modeling. In addition, the model can be applied to verify the rationality of other control calculate ways, and offers a new thoughtway for designing and debugging actual motors.About the control system of DSP,the hardware and software design of the control system is dissertated in detail.The part of the hardware design first expounds the whole design.Then the design of several primary circuits is discussed and choice of some important electronic components and their parameters in these circuits is analysed emphatically.The part of software design also first exprounds the whole design.Next, a few primary sub routines are expatiated.At last,the"software in place of hardware"strategy of the whole control system is presented.After we apply the design scheme of the thesis to a BLDCM,the experimental results indicate that the control system of DSP can make the motor start successfully,the time of startup is less than 3 seconds.And what's more,the control system realizes the motor's correct commutation and smooth running.