Research And Designe On Speed Control Of Brushless DC Motor

The brushless DC motor(BLDCM) is a new style motor in recent years whoseelectronic commutator is used instead of mechanical one, which overcomes a seriesof disadvantages of the traditional DC motor caused by the brush friction withelectrical sparkle、motor loss and noise. Furthermore, BLDCM has many advantages,such as small volume, good regulating performance, large output torque and highefficiency. With the development of power electronics and new permanent magneticmaterials, it is widely applied to every field of national industry and people’s dailylives with broad market prospects, therefore, study on the control system forBLDCM has important theoretical and practical significance. The paper chooses thespeed control system of BLDCM as the main object of research, its speed controlmethod has been studied.Firstly, the research background and significance of the brushless DC motorcontrol are elaborated. Then the control technology development history and thecurrent study of domestic and international of the BLDCM are introduced andfocusing on analysis of PID control, variable structure control, fuzzy control andneural network control system and so on.Secondly, the operation principle and speed control method is deduced in detailbased on the structure and mathematical model of BLDCM. BLDCM is a nonlinear,multivariable system, the traditional PID control is difficult to meet itshigh-precision control, therefore, a fuzzy PID controller is designed and applied tothe speed outer loop control of the brushless DC motor system combining with thecharacteristics of fuzzy control and PID control, then the simulation model of theBLDCM speed control system in MATLAB is built. Simulation results show that theuse of fuzzy PID control system make response speed fast, whose dynamic and staticcharacteristics and robust performance is better than that of PID control. As theperformance of fuzzy control is based on the fuzzy rules, the generation andadjustment of rules always rely on expert’experience, To further enhance the overallperformance of control system, combining the neural network adaptive control basedon the improvement of fuzzy PID control, a quadratic single neuron fuzzy adaptivePID controller is designed on the speed outer loop. The simulation results show thatthe quadratic neuron fuzzy PID control achieved good control effectiveness, which is both better than the traditional PID control and fuzzy PID control.Finally, the brushless DC motor speed control system based on DSP2407 onhardware and software has been designed. Meanwhile, studying through experimentsof the system is done, and the experimental results coincide with the theoreticalanalysis. The hardware part mainly includes power driving circuit, rotor positiondetection circuit, the phase current detection circuit, the speed given and displayingcircuit. The software part mainly constitute completion of the main program and theinterrupt service program. The main program achieves system initialization, theprocess of motor starting and calling interrupt service routine in a loop. Theinterrupt service program includes the interrupt subroutine of capturing positionsignal and A/D conversion.