Research On Control System Of Low Torque Ripple Permanent Magnet Brushless DC Motor

Since the 1980 s,permanent magnet brushless DC(PMBLDC)motors have become an important branch of variable speed motors and have found wide applications in various fields.However,with the development of science and technology,people are more and more demanding on control.The inherent torque ripple problem of PMBLDC motor has seriously affected its development in the field of high-precision control,and has drawn wide attention.Although many literatures provide a method to suppress the torque ripple of PMBLDC motor,most of them are only based on theoretical analysis and simulation.In this paper,the PM rotational angular acceleration sensor is used to measure the torque ripple waveform of the typical product of the PMBLDC motor.which not only shows that the pulsation problem is still serious,but also found that its waveform is very close to the sine wave.This is a completely new finding from previous simulation studies,and provides a new way to solve this problem.This is quite different from the previous simulation studiesIn response to this situation,this paper analyzes the principle of PMBLDC motor and its torque ripple generation mechanism,and theoretically verifies that the torque ripple waveform is a symmetrical waveform close to the sine wave.On this basis,a method of suppressing torque ripple of PMBLDC motor based on the principle of complementary peaks and valleys is proposed,that is,two torque ripples with the same amplitude,the same frequency and the opposite phase are generated by the motor,then,the two torque ripple waveforms are suppressed by the peak-valley complementation,based on this technical idea,the PMBLDC motor model with low torque ripple constituted by wo stator and rotor systems is proposed;The control system of the motor was developed,while controlling the two stator and rotor systems,considering the discrepancy of the mechanical characteristics of the two motor systems consisting of two stators and rotors,it is impossible to control the two sets of stator and rotor systems respectively to achieve the same load rate,constant torque operation under the same speed.Therefore,a control drive system is proposed to control the two motor systems through the current coordination control method,and the two drive systems form a current coordination.The two motors are controlled to work at close mechanical characteristics,so as to realize the control of the two motor systems at the same speed,the same speed and the same load rate,and control the two average torque generated by the two motor systems to mutually superpose the driving loads.Meanwhile,the two torque ripple amplitudes are controlled to be the same,Peak and valley complement each other to achieve low torque ripple.The whole control system consists of voltage regulator circuit,drive circuit,feedback circuit,current coordination,control module and so on.This paper completed the design and development of related circuits,and completed the development of related control hardware and software system on DSP control chip,realizing the control of the same direction,same speed and same load rate of the two motor systems,after being coupled with the motor,the performance is good and the torque ripple of the motor is greatly restrained.The validity of the PMBLDC motor with low torque ripple and its control system based on the principle of complementary peaks and valleys is proved.The above research has opened up a new way for the torque ripple suppression of PMBLDC motor.The successful development of this controller has laid a good foundation for the development of PMBLDC motor system with low torque ripple,it is significant to promote the popularization and application of PMBLDC motor.