Research On Sensorless Vector Control Technology Of Brushless DC Motor

Owing to the advantages of simple structure, high efficiency and good reliability, BLDCM has been widely used in industrial and commercial fields. The square-wave control method is widely used to drive BLDCM, but the method has the disadvantages of large torque ripple and big noise. For BLDCM with fractional slot winding which makes that back-EMF is sine wave, the vector control method can improve the performance of the system. In this regard, the sensorless vector control method of brushless DC motor is researched in this paper, the main research contents are as follows:(1)Based on the analysis of vector control and BLDCM, the mathematical model of BLDCM is established under the condition of vector control. According to the analysis and comparison of control strategy, id=0 is chosen combined with the actual situation.(2)The method of initial position detection and the starting under the condition of BLDCM zero / low speed are analyzed. According to the actual requirement of control system, after the comparison of predetermined position method, wide voltage pulse injection method and high frequency pulse signal injection method on advantages and disadvantages, wide voltage pulse injection method is selected actually.(3)The improved sliding mode observer is proposed based on the study of the principle of the sliding mode observer and the reason of the chattering problem. The new scheme uses improved sigmoid function instead of the traditional switch function, and extracts the rotor position and speed information by PLL structure, and is compared with the traditional sliding mode observer through the simulation and physical experiments to verify the effectiveness of the improved sliding mode observer in reducing chattering and improving the estimation accuracy.(4)In the design of the system physics experiment platform with STM32F103RCT6 as master chip,the lower machine system and GUI PC software are programmed and debugged. The sensorless vector control of BLDCM is realized, and the feasibility and correctness of the scheme are also verified.