Abstract
In a self-sensing active magnetic bearing (AMB) system driven by pulse width modulation (PWM) switching power amplifiers, the rotor position information can be extracted from coil current and voltage signals by a specific signal demodulation process. In this study, to reduce the complexity of hardware, the coil voltage signal was not filtered but measured in the form of a duty cycle by the eCAP port of DSP (TMS320F28335). A mathematical model was established to provide the relationship between rotor position, current ripple, and duty cycle. Theoretical analysis of the amplitude-frequency characteristic of the coil current at the switching frequency was presented using Fourier series, Jacobi-Anger identity, and Bessel function. Experimental results showed that the time-varying duty cycle causes infinite side frequencies around the switching frequency. The side frequency interval depends on the varying frequency of the duty cycle. Rotor position can be calculated by measuring the duty cycle and demodulating the coil current ripple. With this self-sensing strategy, the rotor system supported by AMBs can steadily rotate at a speed of 3000 r/min.
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References
Garcia, P., Guerrero, J.M., Briz, F., Reigosa, D.D., 2010. Sensorless control of three-pole active magnetic bearings using saliency-tracking-based methods. IEEE Trans. Ind. Appl., 46(4):1476–1484. [doi:10.1109/TIA.2010.2049973]
Li, L.C., Shinshi, T., Shimokohbe, A., 2004. State feedback control for active magnetic bearings based on current change rate alone. IEEE Trans. Magn., 40(6):3512–3517. [doi:10.1109/TMAG.2004.836295]
Maslen, E.H., 2006. Self-Sensing for Active Magnetic Bearings: Overview and Status. Proc. 10th Int. Symp. on Magnetic Bearings, p.13–19.
Maslen, E.H., Iwasaki, T., Mahmoodian, R., 2006. Formal Parameter Estimation for Self-Sensing. Proc. 10th Int. Symp. on Magnetic Bearings, p.206–210.
Montie, D.T., 2003. Performance Limitations and Self-Sensing Magnetic Bearings. PhD Thesis, University of Virginia, USA.
Noh, D., 1997. Self-Sensing Magnetic Bearings Driven by a Switching Power Amplifier. PhD Thesis, University of Virginia, USA.
Okada, Y., Matsuda, K., Nagai, B., 1992. Sensorless Magnetic Levitation Control by Measuring the PWM Carrier Frequency Component. Proc. 3rd Int. Symp. on Magnetic Bearings, p.176–183.
Ranft, E.O., van Schoor, G., du Rand, C.P., 2011a. Self-sensing for electromagnetic actuators. Part I: a coupled reluctance network model approach. Sens. Actuat. A, 172(2):400–409. [doi:10.1016/j.sna.2011.09.041]
Ranft, E.O., van Schoor, G., du Rand, C.P., 2011b. Self-sensing for electromagnetic actuators. Part II: position estimation. Sens. Actuat. A, 172(2):410–419. [doi:10.1016/j.sna.2011.09.037]
Schammass, A., Bleuler, H., 2002. Experimental Result on Self-Sensing AMB Using a Three-State PWM Amplifier. Proc. 8th Int. Symp. on Magnetic Bearings, p.289–292.
Schammass, A., Herzog, R., Buhler, P., Bleuler, H., 2005. New results for self-sensing active magnetic bearings using modulation approach. IEEE Trans. Control Syst. Technol., 13(4):509–516. [doi:10.1109/TCST.2004.843142]
Sivadasan, K.K., 1996. Analysis of self-sensing active magnetic bearings working on inductance measurement principle. IEEE Trans. Magn., 32(2):329–334. [doi:10.1109/20.486516]
Tang, M., Zhu, C.S., 2010. New Method of Position Estimation for Self-Sensing Active Magnetic Bearings Based on Artificial Neural Network. Int. Conf. on Electrical and Control Engineering, p.1355–1358. [doi:10.1109/iCECE.2010.336]
Vischer, D., 1988. Sensorlose und Spannungsgesteuerte Magnetlager. PhD Thesis, No. 8665, Department of Mechanical Engineering, Swiss Federal Institute of Technolology, Zurich, Switzerland.
Vischer, D., Bleuler, H., 1990. A New Approach to Sensorless and Voltage Controlled AMBs Based on Network Theory Concepts. Proc. 2nd Int. Symp. on Magnetic Bearings, p.301–306.
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Project (No. LZ13E070001) supported by the Natural Science Foundation of Zhejiang Province, China
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Tang, M., Zhu, Cs. & Yu, J. Self-sensing active magnetic bearing using real-time duty cycle. J. Zhejiang Univ. - Sci. C 14, 600–611 (2013). https://doi.org/10.1631/jzus.C1300023
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DOI: https://doi.org/10.1631/jzus.C1300023