Initial Rotor Position Detection for Brushless DC Motors Based on Coupling Injection of High-Frequency Signal

ABSTRACT:

 In applications where motor inversion is forbidden, it is important to detect the initial rotor position of the motor. For this reason, based on coupling injection of high-frequency signal, a novel method of initial rotor position detection for brushless DC motors (BLDCM) is proposed in this paper. Firstly, the proposed method detects the relationship between three-phase winding inductances by injecting the high frequency detection signal into motor windings in a coupling way, and the initial rotor position is determined into two sectors with 180 degrees electric angle difference. Then, the polarity of the permanent magnet rotor is determined by applying two opposite voltage vectors to motor windings, so that the initial rotor position is determined into a unique sector, and the positioning accuracy is 30 degrees electric angle. The proposed method significantly reduces the amplitude of the detection signal while increases its frequency by the way of coupling injection, thus reducing the response current and electromagnetic torque generated by the high-frequency signal and reducing the possibility of rotor inversion. Finally, the effectiveness of the proposed method is verified by experimental results.

KEYWORDS:

1.      Brushless DC motor

2.      Initial rotor position

3.      High-frequency signal

4.      Coupling injection

SOFTWARE:MATLAB/SIMULINK

 CONCLUSION:

In this paper, the relationship between winding inductances and the rotor position of BLDCM is analyzed in detail, and a novel method of initial rotor position detection based on high-frequency signal coupling injection is proposed. The initial rotor position can be determined into a sector with 30 degrees electric angle. The proposed method overcomes the limitations of fixed DC-link voltage and limited switching frequency of the inverter by the way of coupling injection, and significantly reduces the amplitude of the detection signal while increases its frequency. Experimental results show that, compared with traditional methods, the method proposed in this paper can accurately detect the initial rotor position and effectively reduce the electromagnetic torque, thus reducing the possibility of rotor inversion in the process of initial position detection.

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