A Novel Torque Ripple Reduction Strategy For Brushless DC Motor

Brushless DC Motor(BLDCM)is widely used in the field of automative,aerospace and household appliances due to its inherent merits of easy control,high power density,good mechanical properties and so on.However,the torque ripples of BLDCM under the traditional control methods lead to the problems of vibration,heating and noise,and sometimes BLDCM is taken place by(Permanent Magnetic Synchronous Motor)PMSM in the high precision requirement applications.Therefore,in this paper,a new torque ripple suppression method for BLDCM is proposed to solve the above issues.Firstly,the mathematical model and operation princ iple of BLDCM is introduced,the cause of torque ripples is analyzed from two aspects of the non-commutation process and the commutation process.In the non-commutation process,the torque ripples caused by non-ideal back EMF and diode-freewheeling of inactive phase are focused on,and the angle of the stator flux linkage is used to analyze the commutation torque ripples.Then,a strategy based on average power control is proposed to minize the non-commutation torque ripples of BLDCM,the average power delivered from DC power supply in each PWM per iod is used as the control object in the control method.The double closed loop control structure with the outer speed loop and inter power loop is adopted to control the ouput torque indirectly in order to ensure the smooth output of torque during the non-commutation process.Furthermore,a novel commutation torque ripple suppression method with the three-phase conducting voltage space vector insertion during the commutation state is given.The active time of the three-phase conducting voltage space vector is derived by the current change rate of open-phase and closed-phase winding,then,the weighting fomulas of duty cycle for the three-phase voltage space vector are calculated respectly according to different PWM mode to extend the application fields.Finally,the simulation model based on the control strategy of this paper is built by Matlab/S imulink,and the system experimental platform based on DSP2812 and CPLD is also established.The validity and effectiveness of the proposed novel BLDCM torque ripple suppression strategy is verified by the simulation and the experimental results.