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Sensors 2013, 13(9), 12149-12165; doi:10.3390/s130912149
Article

A Self-Sensing Active Magnetic Bearing Based on a Direct Current Measurement Approach

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Received: 14 July 2013; in revised form: 18 August 2013 / Accepted: 29 August 2013 / Published: 11 September 2013
(This article belongs to the Section Physical Sensors)
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Abstract: Active magnetic bearings (AMBs) have become a key technology in various industrial applications. Self-sensing AMBs provide an integrated sensorless solution for position estimation, consolidating the sensing and actuating functions into a single electromagnetic transducer. The approach aims to reduce possible hardware failure points, production costs, and system complexity. Despite these advantages, self-sensing methods must address various technical challenges to maximize the performance thereof. This paper presents the direct current measurement (DCM) approach for self-sensing AMBs, denoting the direct measurement of the current ripple component. In AMB systems, switching power amplifiers (PAs) modulate the rotor position information onto the current waveform. Demodulation self-sensing techniques then use bandpass and lowpass filters to estimate the rotor position from the voltage and current signals. However, the additional phase-shift introduced by these filters results in lower stability margins. The DCM approach utilizes a novel PA switching method that directly measures the current ripple to obtain duty-cycle invariant position estimates. Demodulation filters are largely excluded to minimize additional phase-shift in the position estimates. Basic functionality and performance of the proposed self-sensing approach are demonstrated via a transient simulation model as well as a high current (10 A) experimental system. A digital implementation of amplitude modulation self-sensing serves as a comparative estimator.
Keywords: self-sensing; active magnetic bearing (AMB); direct current measurement (DCM); position estimation; magnetic suspension; duty cycle self-sensing; active magnetic bearing (AMB); direct current measurement (DCM); position estimation; magnetic suspension; duty cycle
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Niemann, A.C.; van Schoor, G.; du Rand, C.P. A Self-Sensing Active Magnetic Bearing Based on a Direct Current Measurement Approach. Sensors 2013, 13, 12149-12165.

AMA Style

Niemann AC, van Schoor G, du Rand CP. A Self-Sensing Active Magnetic Bearing Based on a Direct Current Measurement Approach. Sensors. 2013; 13(9):12149-12165.

Chicago/Turabian Style

Niemann, Andries C.; van Schoor, George; du Rand, Carel P. 2013. "A Self-Sensing Active Magnetic Bearing Based on a Direct Current Measurement Approach." Sensors 13, no. 9: 12149-12165.


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