Study On Sensorless Control Of Permanent Magnet Brushless DC Motor (PMBLDCM)

Permanent Magnet Brushless DC Motor (PMBLDCM), as a kind of typical integrated electromechanical products with superiority and brilliant function, has been growing extensively in past decades.Nowadays, the research on sensorless control of PMBLDCM has become more and more absorbing. Concluding several common-used sensorless methods, the back-EMF (electromotive force) method and the third-harmonic of rotor flux method are analyzed in detail, then the reasons to cause the position estimation error are analyzed and corresponding improved schemes are given at last.Based on ML4425 produced by FairChild, a general sensorless controller for PMBLDCM in small/middle power range is assembled. Using a differential circuit, a hybrid speed and current control is implemented to limit the current. The prospect of the controller is discussed based on the experiment results.Based on the method on third-harmonic of rotor flux, a novel method for detecting rotor position by analyzing the harmonic signals of back-emf is proposed. A system of modeling and simulation is constructed by Matlab/Simulink, the real-time simulation is adopted to increase the simulation speed. A general plate for motor simulation is developed for both DOS and Windows system based on the RealTime Workshop (RTW) of MATLAB and Visual C++. A practicable control system based on TMS320F240 is implemented, and the improvement scheme is proposed based on the experiment results.