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Self-Sensing Magnetic Bearings Driven by a Switching Power Amplifier. (1996)

by M D Noh
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PREFACE

by Eugen O. Ranft, Promoter G. Van Schoor , 2007
"... An improved model for self-sensing heteropolar active magnetic bearings ..."
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An improved model for self-sensing heteropolar active magnetic bearings
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... due to the dynamics of the suspended object being coupled to the bearingsthrough back electro-motive-force (EMF). The inherent coupling of sensing and control signals issalso a serious drawback [4], =-=[32]-=-.sPractical applicationssIn [33] a practical application of the state estimation approach is presented where for the first timesa rotor was suspended in four radial degrees of freedom without position...

Self-Sensing in Fault Tolerant Magnetic Bearings III I II I MIM I 111 El

by Dominick Montie , Eric Maslen
"... ABSTRACT Several schemes have recently been proposed for achieving either fault tolerance or self-sensing in magnetic bearings. The present work describes the fundamental connection between ability to actuate and ability to sense in a partially failed magnetic bearing system. This relationship is t ..."
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ABSTRACT Several schemes have recently been proposed for achieving either fault tolerance or self-sensing in magnetic bearings. The present work describes the fundamental connection between ability to actuate and ability to sense in a partially failed magnetic bearing system. This relationship is then exploited to construct a selfsensing scheme which operates in the presence of detectable actuator or amplifier faults. Such an approach is advantageous in fault tolerant systems because it reduces or eliminates the need to address potential independent failure mechanism's in sensors and actuators. Based on a model reference parameter estimation mechanism, the self-sensing scheme is shown to provide acceptable position measurement accuracy and bandwidth under various actuator/amplifier faults which are actuator tolerable. Estimates of increase in noise floor and loss of bandwidth under fault conditions are provided. The issue of estimator convergence under fault conditions is examined in detail with comments on implementation complexity arising from scheduling convergence control on fault state.
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...(13 microseconds in the simulation). The result is stable current control with a switching limit cycle with overall period of 52 microseconds: about 20 kHz. Similar behavior would be obtained with any of a number of other switching algorithms. The target currents determine the force produced by the actuator. Meeker[5] provides a thorough coverage of this in both the nominal case and when the actuator has a fault. For the simulations here, the target currents were held at a nominal bias condition, so the effect of target current dynamic behavior was not examined. For the single magnet case, Noh[7] provides an extensive discussion of the effect of dynamic current reference. FAULT CONDITIONS The fault mechanism addressed in this work is an open circuit at any point in the series connection of amplifier, wiring, and coil. Such a fault includes fuse burnout, amplifier device burnout (in the open condition), coil wire burnout, and connector failure. It does not consider the shorted coil scenario or other short failures as in the power amplifier. In open circuit failures, the coil current goes to zero: for short failures, the coil voltage goes to zero and the current is driven by stator flux...

1 ABSTRACT Self-Sensing in Fault Tolerant Magnetic Bearings

by Dominick Montie, Eric Maslen
"... Several schemes have recently been proposed for achieving either fault tolerance or self-sensing in magnetic bearings. The present work describes the fundamental connection between ability to actuate and ability to sense in a partially failed magnetic bearing system. This relationship is then exploi ..."
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Several schemes have recently been proposed for achieving either fault tolerance or self-sensing in magnetic bearings. The present work describes the fundamental connection between ability to actuate and ability to sense in a partially failed magnetic bearing system. This relationship is then exploited to construct a selfsensing scheme which operates in the presence of detectable actuator or amplifier faults. Such an approach is advantageous in fault tolerant systems because it reduces or eliminates the need to address potential independent failure mechanisms in sensors and actuators. Based on a model reference parameter estimation mechanism, the self-sensing scheme is shown to provide acceptable position measurement accuracy and bandwidth under various actuator/amplifier faults which are actuator tolerable. Estimates of increase in noise floor and loss of bandwidth under fault conditions are provided. The issue of estimator convergence under fault conditions is examined in detail with comments on implementation complexity arising from scheduling convergence control on fault state. 2
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...reliability. Selfsensing reduces the initial costs and size of the system/ It also increases reliability by removing a failure susceptible part. While many self-sensing schemes have been demonstrated =-=[3, 6, 7, 8]-=-, this technology has not been incorporated into a fault tolerant system. This combination of fault tolerance and self– sensing is crucial to successful application of magnetic bearings to machinery w...

IOS Press Modeling of Switching Ripple Currents

by Current Effects, Yongsheng Tian, Yanhua Sun, Lie Yu
"... (SRCs) for magnetic bearings including eddy ..."
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(SRCs) for magnetic bearings including eddy
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