Research On Torque Ripple Suppression Strategy In The Whole Speed Range Of Brushless DC Motors

Recent years brushless direct-current machine has been widely used in the field of civil household appliances,especially the air conditioning motor because of the characteristics of simple structure,small size,light weight and high efficiency.However,the torque ripple of the motor is relatively large because of its delayed winding current,which affects its promotion and application in more occasions.The purpose of this study is to solve the problem of torque ripple when the control system appling in engineering.Firstly,based on the traditional five PWM modulation methods,a modified PWM modulation method based on sector segmentation was proposed to suppress the pulsation of the commutation current.Then,an improved highprecision position signal acquisition method based on hall sensor is proposed to reduce the control cost of BLDCM.Finally,based on the different characteristics of the motor working in low speed and high speed,the combination of direct torque control method and overlapping commutation method is proposed to reduce torque ripple in both speed range.All the methods is validated by experiment.In general,the work of this thesis lays the theoretical foundation for the further research and pratical applications.The main research contents and results are as follows.:(1)The research analyzes the composition and working principle of brushless dc motor,and introduces its application and existing problems in the industrial field.By analyzing and summarizing the current research status of BLDCM control technology at home and abroad,the paper points out the advantages and disadvantages of the existing control methods of BLDCM.(2)An improved PWM modulation method is proposed on the basis of the traditional four PWM modulation methods to reduce the commutation torque ripple.(3)A modified method using low accuracy position sensor to get high accuracy position signal was proposed and can reduce the control cost of BLDCM and improve the accuracy of speed and position signal estimation in motor dynamic process.(4)In order to solve the commutation torque ripple in both high speed and low speed,method by combing the direct torque control and overlapping commutation method is proposed.(5)The simulation model of the related BLDCM drive system is established based on the MATLAB/Simulink.DSP28069 M was used for experimental verification.