A Position Sensorless Control Strategy for BLDCM Based on Flux-Linkage Function

 ABSTRACT:

 A novel sensorless control strategy for the brushless DC motor (BLDCM) is proposed in this paper. The proposed strategy is realized by employing new flux-linkage functions, and can be applied to drive the sensorless BLDCM in the high speed and low speed ranges with highly accurate and reliable commutation. Another attractive feature is that the jumping edges of the flux-linkage functions are utilized to determine the commutation points, so there is no threshold needed as comparing with other sensorless control methods. In addition, the three-phase current control method is adopted, and terminal voltages in flux-linkage function expressions can be easily obtained by calculation. By this way, the sample delay and the influence of the floating phase voltage can be eliminated which can improve the accuracy and reliability of the sensorless control strategy. The effectiveness of the proposed strategy is verified by experimental results.

KEYWORDS:

1.      Brushless dc motor

2.      Flux-linkage function

3.      Sensorless

4.      Rotor position.

 SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

In this paper, a novel flux-linkage function was constructed. The relationship between the flux-linkage function and the commutation point has been analyzed, and the jumping edge is used to estimate the commutation point. A rotor-position table is established, and then the sensorless control principle of the flux-linkage function is illustrated. In conclusion, the proposed strategy has the following advantages.

1) The flux-linkage function is constructed by using the line to line PM flux linkage, whose magnitude is almost constant during the operation. At the same time, the waveform of the flux-linkage function is identical, so the proposed method is suitable for the high speed and low speed ranges and has a small commutation error.

2) The commutation point is obtained by the jumping edge of flux-linkage function without setting commutation threshold, which can reduce the commutation error caused by the unreasonable threshold setting. Meanwhile, the flux-linkage function is significantly large near extreme points, which makes it easier to detect the commutation point.

3) The three-phase current control method is adopted, so the terminal voltage of the flux-linkage function is calculated by the switching state of the power transistor. Therefore, the sampling circuit is not needed, and the error caused by sampling is avoided.

REFERENCES:

[1] C. L. Xia, G. K. Jiang, W. Chen, and T. N. Shi, “Switching-gain adaption current control for brushless DC Motors,” IEEE Trans. Ind. Electron., vol. 63, no. 4, pp. 2044–2052, Apr. 2016.

[2] C. L. Xia, Y. F. Wang, and T. N. Shi, “Implementation of finite-state model predictive control for commutation torque ripple minimization of permanent-magnet brushless DC motor,” IEEE Trans. Ind. Electron., vol.60, no.3, pp. 896–905, Mar. 2013.

[3] T. N. Shi, Y. T. Guo, P. Song, and C. L. Xia, “A new approach of minimizing commutation torque ripple for brushless DC motor based on DC-DC converter,” IEEE Trans. Ind. Electron., vol.57, no.10, pp. 3483–3490, Oct. 2010.

[4] J. C. Moreira, “Indirect sensing for rotor flux position of permanent magnet AC motors operating over a wide speed range,” IEEE Trans. Ind. Appl., vol. 32, no. 6, pp. 1394–1401, Nov./Dec. 1996.

[5] J. X. Shen, Z. Q. Zhu, and D. Howe, “Sensorless flux-weakening control of permanent-magnet brushless machines using third harmonic back emf,” IEEE Trans. Ind. Appl., vol. 40, no. 6, pp. 1629–1636, Nov./Dec. 2004.