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Self-Sensing versus Reference Air Gaps

Authors: Alexander Schulz, Ingrid Rottensteiner, Manfred Neumann, Michael Wehse, Johann Wassermann


Self-sensing estimates the air gap within an electro magnetic path by analyzing the bearing coil current and/or voltage waveform. The self-sensing concept presented in this paper has been developed within the research project “Active Magnetic Bearings with Supreme Reliability" and is used for position sensor fault detection. Within this new concept gap calculation is carried out by an alldigital analysis of the digitized coil current and voltage waveform. For analysis those time periods within the PWM period are used, which give the best results. Additionally, the concept allows the digital compensation of nonlinearities, for example magnetic saturation, without degrading signal quality. This increases the accuracy and robustness of the air gap estimation and additionally reduces phase delays. Beneath an overview about the developed concept first measurement results are presented which show the potential of this all-digital self-sensing concept.

Keywords: digital signal analysis, active magnetic bearing, reliability, fault detection.

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[1] R. Gurumoorthy,W. L. Soong, J. P. Lyons, and A. F. Storace. Implementation of sensorless control of radial magnetic bearings. in Proc. MAG -95 - Magnetic Bearings, Magnetic Drives and Dry Gas Seals Conference & Exhibition, pages 239-248, Alexandria, Virginia, August 10-11 1995.
[2] B. V. Jayawant, B. E. Dawson, R. J. Whorlow, and J. C. Peyton Jones. Digitally controlled transducerless magnetic suspension system. in IEE Proceedings of Science, Measurement and Technology, volume 143, pages 47 - 51, January 1996.
[3] L. Kucera. Robustness of self-sensing magnetic bearing. in Proc. Magnetic Bearings Industrial Conf., pages 261 - 270, Alexandria, VA, 1997.
[4] Lichuan Li, T. Shinshi, and A. Shimokohbe. State feedback control for active magnetic bearings based on current change rate alone. IEEE Transactions on Magnetics, 40(6):3512 - 3517, November 2004.
[5] D. Montie. Performance Limitations and Self-Sensing Magnetic Bearings. PhD-thesis, University of Virginia. January 2003.
[6] M.D. Noh and E.H. Maslen. Self-sensing magnetic bearings using parameter estimation. IEEE Transactions on Instrumentation and Measurement, 46(1):45 - 50, February 1997.
[7] Y. Okada, K. Matsuda, and B. Nagai. Sensorless magnetic levitation control by measuring the PWM carrier frequency component. in Proc. 3rd Int. Symp. on Magnetic Bearings, pages 176-183, Alexandria, Virginia, July 29-31 1992.
[8] A. Schammass, R. Herzog, P. Buehler, and H. Bleuler. New results for self-sensing active magnetic bearings using modulation approach. IEEE Transactions on Control Systems Technology, 13(4):509 - 516, July 2005.
[9] A. Schulz, M. Neumann, J. Wassermann, A Sophisticated Active Magnetic Bearing System with Supreme Reliability, in Proc. 11th Int. Symp. on Magnetic Bearings, Nara, Japan, Aug. 26-29 2008.
[10] A. Schulz, A. Gamez Sangra M. Neumann, J. Wassermann, Modelling and simulation of a sophisticated active magnetic bearing system, in Proc. X. Int. Conf. Theory of Machines and Mechanisms, IFToMM, Liberec, Czech Repub., Sep. 2-4 2008
[11] A. Schulz, M. Neumann, J. Wassermann, A Sophisticated Concept for Supreme AMB Reliability, in Proc. 9th International Conference on Motion and Vibration Control - Movic 2008, Munich, Germany, Sep. 15-18 2008.
[12] A. Schulz, M. Neumann, J. Wassermann, Modeling and Simulation of a Hot-Swap Controller Amplifier Module for an Active Magnetic Bearing with Supreme Reliability, in Proc. 9th International Conference on Modeling and Simulation of Electric Machines, Converters and Systems - Electrimacs 2008, Quebec, Can., Jun. 8-11.
[13] A. Schulz, Simulation eines ausfallsicheren aktiven Magnetlagers, in Proc. Schwingungen in rotierenden Maschinen - SIRM 2009, Vienna, Austria, February 23-25 2009.
[14] A. Schulz, A hot-swap controller amplifier module for active magnetic bearings with supreme reliability - electronic circuitry and error detection strategies, in Proc. 20th International Symposium on Power Electronics, Electrical Drives, Automation and Motion - Speedam 2010, Pisa, Italy, June 14-16 2010.
[15] A. Schulz, An All-Digital Self-Sensing Concept, IEEE Transactions on Magnetics, (not published - in preparation)
[16] G. Schweizer, E.H. Maslen, Magnetic Bearings: Theory, Design, and Application to Rotating Machinery, Berlin Heidelberg: Springer-Verlag, 2009.
[17] P. Tsao, S.R. Sanders, and G. Risk. A self-sensing homopolar magnetic bearing: analysis and experimental results. in Proc. Industry Applications Conference, volume 4, pages 2560 - 2565, October 3 - 7 1999.
[18] D. Vischer. Sensorlose und spannungsgesteuerte Magnetlager. PhD thesis, Eidgenössische Technische Hochschule (ETH) Zurich, Switzerland, 1988.