The Research Of Six-phase Brushless Direct Current Motor Control System

Brushless DC motor using electronic commutation technology to replace the traditional DC motor brush commutation,retain the superior performance of the DC motor,such as large starting torque,fast speed respone and other characteristics,also has AC motor's advantages such as simple structure,easy maintenance and reliable operation,etc.,And the rotor uses permanent magnet material excitation without excitation loss.With the development of the new permanent magnetic material and electronic technology,the application of Brushless DC motor in the national economy is greatly promoted.At present,there are generally used in many fields such as military equipment,aerospace,amusement facilities,electric vehicles and so on.Therefore,the research and development of high performance brushless DC motor control system has good economic and social benefits.Firstly,this thesis describes the domestic and foreign research significance and research status of the brushless DC motor,and then from the basic structure of the motor,detailed describes its working principle is the research object of this thesis(six-phase asymmetric no brush DC motor)mathematical model,including voltage equation and back EMF equation,electromagnetic torque and mechanical motion equation.Torque ripple is always one of the hot spot of brushless DC motor,which is difficuit to solve,this thesis from the back EMF,cogging,armature reaction,motor technology and motor commutation several aspects analysis of the motor's torque ripple.Focuses on the commutation torque ripple,and through mathematical formula derivation,it is concluded that during commutation,the main reason of commutation torque ripple is that the current decline rate of the off phase and the rise rate of the turn-on phase current are not equal,which cause the non-commutation of the phase current ripple,so that torque ripple appears.Comparison of the effect of six common modulation modes for the commutation torque ripple,and selected an suitable modulation——pwm_on_pwm,then the motor run in the low and high speed condition for phase torque ripple are proposed corresponding suppression strategy:at low middle speed based on pwm_on_pwm modulation mode of the non-commutation phase current hysteresis control method,at high speed additional overlapping commutation control.Followed by Matlab/Simulink software to build the simulation model of six-phase asymmetric BLDCM motor,using the control strategy of speed and current double closed loop control,and the simulation waveform is analyzed in detail,to verify the correctness of the proposed suppression strategy.Finally,on the basis of previous theory and simulation,the controller of the six-phase asymmetric BLDCM is designed with the TMS320F28335DSP chip as the control core,and introduces the controller's hardware,software and the upper computer.The experimental platform of the control system is established,and the system is debugged.The results show that the control algorithm and modulation method are correct and effective.