Research On Direct Torque Control Method Of Position Sensorless Brushless DC Motor Based On Duty Cycle Adjustment

Brushless DC Motor(BLDCM)is widely used in industry with its simple structure,high reliability and high efficiency characteristics.With the adaption of the sensorless detection technology,the size of motor is greatly reduced.But the application of BLDCM in the high speed and precision area is limited due to the disadvantage of its torque ripple.The Direct Torque Control(DTC)of Brushless DC Motor with Sensorless based on duty cycle control is studied to minimize the torque ripple of BLDCM in this paper,the simulation result verifies that the new method can minimize the torque ripple efficiently.The hardware experimental platform system is built,and the experimental results verify the feasibility of this new method.This paper mainly does the following researches:Firstly,the operational principle of BLDCM and DTC is analyzed;an improved DTC control method with duty cycle control is presented;the method,how to realize sensorless control system of BLDCM by adapting the back electromagnetic force(back-EMF)zero-crossing detection method is studied,and fast pre-location under sensorless control system is studied.The result of simulation and experiment confirm its feasibility.Then,in view of the mathematical model of BLDCM,the BLDCM control method simulation model is designed in Matlab/Simulink,and the simulation model of DTC with duty cycle control is confirmed feasibility by the result.Meanwhile,the magnetic field distribution and back-EMF of different rotor and stator structure is studied to minimize the torque ripple by ansoft simulation software.At last,a hardware experimental platform system is set up;the sensorless BLDCM running process is programed.The contrast of the improved and the traditional DTC are done on the experimental platform,and the experimental results verify the feasibility of the improved DTC.