A Novel Direct Self Control Strategy For PM Brushless DC Motor

Brushless DC motors(BLDCM)are widely accepted for industrial applications.Owing to their higher torque density and higher efficiency compared with other kinds of motors,recently,BLDCM have attracted numerous attention in the fields including household electric appliances,aerospace,and electric vehicle.Achieving position information of the rotor is one of the necessary conditions for precise control of the BLDCM.But the use of traditional position sensors lead to problems including high cost,installation difficulty of mechanics,and poor reliability.Using easily measured variables such as current and voltage to identify position sign in order to realize sensorless control is a valuable solution.However,sensorless control schemes usually result in problems for the performance of the motor such as narrower speed range,weaker load capacity,and larger torque ripple.Realizing sensorless control,at the same time giving consideration to the performance of the motor has become a hot issue in recent years.The main contribution of this paper is to apply the idea of variable switching point into DSC in the premise of the absence of position sensor.The proposed DSC strategy has relatively smaller torque ripple.Expression of torque variation rates under different voltage vectors are derived,and impact of voltage vectors on the variation of torque is analyzed in order to find the reason of steady state torque ripple.On the basis of such analysis,duration of vector is derived with the control objective of torque ripple minimization.Finally,the idea of VSP is used for pulse generation,which brings about an effective inhibition of torque ripple.In addition,hardware prototype is set up.In order to thoroughly validate effectiveness of the proposed method,experiments under different operation conditions are respectively carried out.