Study On The Sensorless Control System Of Brushless DC Motor

Brushless direct current motor (BLDCM) is a new mechatronic motor based on the advancement of power electronics and new permanent magnet materials. The superiority of sensorless detection of BLDCM is increasingly obvious with the wide application in a variety of fields.Firstly, the status quo of BLDCM sensorless control at home and abroad are analyzed and summarized in this dissertation based on the BLDCM structure and the basic working principle. Some studies have been done deeply around the key issues including how to obtain a reliable signal through software and hardware indirectly. Meanwhile, the start method of"three-stage"is researched and the control strategy of the control system.is given.Secondly, Matlab7.1/Simulink is used to conduct the simulation study of BLDCM and its control system. Double-loop of the speed and current PI regulator are adopted in the simulation system. Simulation results show that the static and dynamic characteristics of BLDCM sensorless control system which is designed in this dissertation are good. First-order RC low-pass filter and back-EMF phase comparator circuits are designed in this paper. Further more, the drive circuit and other hardware circuits are designed for the sensorless control system hardware experimental platform with DSP as the main CPU. The software program of BLDCM sensorless control system is written in assembly language. Meanwhile, "three-stage" start strategy is used to achieve external synchronization start and switching to self-synchronization operation. The phase delay caused by the hardware detection is compensated effectively by using software.Lastly, the experiment platform of BLDCM sensorless control system is set up, and some related experiments are carried out for the control system. The results and analysis of the experiments are also given. The experiment shows that the BLDCM sensorless control system presented and designed in this paper is running with good performance.