Abstract

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Title:: Rotor position estimation based on line-to-line back-EMF for brushless DC motors

Author(s):: ZHANG Xin-rong; ZHANG Li-wei; LIU Hong-ping; ZENG Chun-yan; 1. Key Laboratory of Road Construction Technology and Equipment of the Ministry of Education, Chang’an University, Xi’an 710064, Shaanxi, China; 2. CN Gpower GearboxCo. Ltd., Chongqing 402263, China; 3. CSIC Haisheng Technology Co. Ltd., Yichang 443000, Hubei, China

Keywords:: mechanical engineering; brushless DC motor; rotor position; estimation; line-to-line back-EMF; PWM_ON_PWM modulation

Abstract:: In order to determine the rotor position of brushless DC Motors accurately and effectively, a novel method using reciprocal of simplified line-to-line back-EMF to constructing F functions was proposed for detecting the rotor position of brushless DC motors based on characteristics of the principle of line-to-line back-EMF zero crossing detection method and PWM_ON_PWM modulation method. Through theoretical analysis of relationship between line-to-line back-EMF and rotor position of brushless DC motor, it was proved that the zero-crossing point of line-to- line back-EMF was corresponding to the instant of actual commutation. According to the fact that there is no diode freewheeling of the inactive phase under PWM_ON_PWM modulation, the F function was simplified and real-time calculated by use of PWM_ON_PMN modulation, and the rotor positions of brushless DC motor were estimated by use of simplified F function. Finally the control system of brushless DC motor by use of the rotor position estimation method was simulated by MATLAB/SIMULINK. The results show that the rotor position commutation signal can be detected effectively and simply using the proposed methods. This method does not need to measure the stator inductance or mutual inductance between the stators, only needs to measure the currents and voltages of two phases. In addition, the phase delay compensation is unnecessary. The method has practical engineering value.