The main purpose of this study is to propose a novel back-EMF observer. It can drive a permanent magnet Brushless DC Motor (BLDCM) smoothly from slow to high speed without position or speed sensors. In the method, a phase back-EMF observer, which could estimate phase back-EMFs in real time and only relies on DC voltage and phase currents of motor without an additional circuit or complicated operation process，had been established with phase back-EMF as a disturbance signal. This observer simplifies the structure of traditional back-EMF observers and only has one inertia element, hence the response time and robustness of the system could be improved. This study also detailedly provides a method for speed and position detection, which has high performance in low speed range. The validity of the proposed method is verified through simulation and experimental results.
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