Sensorless BLDC Motor Commutation Point Detection and Phase Deviatio


 Phase-to-neutral voltage or neutral-to-virtual neutral voltage zero-crossing points (ZCPs) detection method is usually used for sensorless BLDC motor commutation control. Unfortunately, neither of them can be realized in lower speed range.


In this paper, a simple commutation point detection method is proposed based on detecting inactive phase terminal to dc-link midpoint voltage.


It eliminates the requirement of neutral wire or virtual neutral voltage and provides an amplified version of back electromotive force (EMF) at the ZCPs which makes the lower speed range detection possible. Sensorless BLDC Motor As the speed increasing, commutation point error is enlarged due to the low pass filter (LPF) et al. Utilizing the symmetry of the terminal to midpoint voltage the phase error can be corrected.


Sensorless BLDC Motor However, due to the nonlinear relationship between the detected voltage difference and phase error, it is difficult to regulate the error fast and robustly. Therefore, a novel phase regulator based on fuzzy neural network (FNN) is proposed


in this paper with simple structure and learning ability. The validity of the proposed ZCPs detection method and commutation instant shift correction method are verified through experimental results.


  1. Brushless dc (BLDC) motor
  2. Commutation signal
  3. Fuzzy neural network
  4. Sensorless motor
  5. Zero-crossing points (ZCPs) detection



Fig. 1Buck converter based BLDC motor drive system topology


Fig. 2 Three kinds of ZCPs detection methods comparison.

Fig. 3 Convergence speed comparison between PI controller and FNN-based controller at 18000rpm.

Fig. 4 Performance comparisons between PI controller and FNN-based controller during 10000rpm~13000rpm.

Fig. 5 Performance comparisons between PI controller and FNN-based controller during 3000rpm~7000rpm.

Fig. 6 Performance comparisons between direct calculation method and FNN-based controller at 5000rpm.

Fig. 7 Speed range tests for the terminal to virtual neutral voltage-based method and the proposed method.

Fig. 8 Transient performances of the proposed method.


Sensorless BLDC Motor In this paper, a novel commutation point detection method is proposed. It is realized based on detecting the ZCPs of inactive phase terminal to dc-link midpoint voltage. Since it provides an amplified version of back-EMF at the ZCPs


this method makes the sensorless driving in lower speed range possible. Then, the relationship between the phase shift and the sampled terminal to midpoint voltage difference is derived, and its influencing factors are analyzed in detail.


Sensorless BLDC Motor Based on this relationship, a robust and fast commutation point phase deviation correction method is proposed based on the FNN controller. The experiments show that the proposed controller is effective in both steady-speed control and variable-speed control.


It exhibits fast convergence behavior in the whole speed range compared with the PI controller, and it presents strong robustness compared with the direct calculation method even if motor parameters have large fluctuations.


[1] W. Jiang, H. Huang, J. Wang, et al, “Commutation Analysis of Brushless DC Motor and Reducing Commutation Torque Ripple in the Two-Phase Stationary Frame,” IEEE Trans. Power Electron., vol. 32, no. 6, pp. 4675–4682, Jun. 2017.

[2] W. Chen, Y. Liu, X. Li, et al, “A Novel Method of Reducing Commutation Torque Ripple for Brushless DC Motor Based on Cuk Converter,” IEEE Trans. Power Electron., vol. 32, no. 7, pp. 5497–5508, Jul. 2017.

[3] S.Zheng, B.Han, L.Guo. Composite Hierarchical Antidisturbance Control for Magnetic Bearing System Subject to Multiple External Disturbances [J]. IEEE Transactions on Industrial Electronics, 2014, 61(12): 7004-7012.

[4] S.Zheng, H.Li, B.Han, J.Yang. Power Consumption Reduction for Magnetic Bearing Systems during Torque Output of Control Moment Gyros [J]. IEEE Transactions on Power Electronics, 2017, 32(7): 5752-5759.

[5] T. Chun, Q. Tran, H. Lee, “Sensorless Control of BLDC Motor Drive for an Automotive Fuel Pump Using a Hysteresis Comparator,” IEEE Trans. Power Electron., vol. 29, no. 3, pp. 1382–1391, Mar. 2014.

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