Abstract
In this paper, a novel sensorless control strategy based on the estimation of line back electro-motive force (BEMF) is proposed. According to the phase relationship between the ideal commutation points of the brushless direct current motor (BLDCM) and the zero-crossing points (ZCPs) of the line BEMF, the calculation formula of line BEMF is simplified properly and the commutation rule for different positions of the rotor is presented. The estimation error of line BEMF caused by the freewheeling current of silent phase is analyzed, and the solution is given. With the phase shift of the low-pass filter considered, a compensation method using “60°-α” and “120°-α” is studied in this paper to eliminate the error. Finally, the simulation and experimental results show that the rotor-position-detection error is reduced effectively and the motor driven by the accurate commutation signal can work well at low and high speed.
Highlights
The brushless direct current motor (BLDCM), a permanent magnet synchronous motor, has been widely used in varieties of applications including aerospace, industrial automation, hybrid vehicles [1], the military field [2], and household products
Most of the conventional sensorless control strategies of BLDCM are based on back electro-motive force (BEMF) detection, which can be classified into two categories: direct and indirect BEMF
zero-crossing points (ZCPs) lag eliminate the error caused by the filter at low and high speed, respectively
Summary
The brushless direct current motor (BLDCM), a permanent magnet synchronous motor, has been widely used in varieties of applications including aerospace, industrial automation, hybrid vehicles [1], the military field [2], and household products. Most of the conventional sensorless control strategies of BLDCM are based on back electro-motive force (BEMF) detection, which can be classified into two categories: direct and indirect BEMF detection [7] The former includes the phase voltage method and terminal voltage method [8,9,10], which are the most widely used methods, yet these sensorless methods have poor, low-speed performance and require filters to suppress high frequency noise, which may induce large phase shifts to the commutation signals at high speed. The terminal voltage detection circuits are omitted as well, which improves the universality of the hardware This method neglects the phase resistance drop, which may cause a calculation error in the line BEMF, and it does not consider the phase shift of the filter either which will cause a large phase delay at high speed.
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