Guidance dynamics of mixed-mu levitators for maglev vehicles

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Guidance dynamics of mixed-mu levitators for maglev vehicles

Mirzamani, S.J. / Paul, R.J.

Mixed-mu levitation is the principle whereby iron is freely levitated in a magnetic field, being stabilized by the proximity of diamagnetic superconducting screen material. For application to MAGLEV ground transport, superconducting field coils and stabilizing screens are mounted in on-board cryogenic levitator pods of the vehicle to give levitation about a mild steel rail. The system exhibits little natural damping and the guidance damping requirements are particularly severe. Preliminary feasibility studies show that reasonable ride characteristics in guidance are obtained using passive damping screens utilizing a secondary suspension and a primary system employing copper sheets attached to the cryostat walls. This paper fully investigates the damping and both static and dynamic stiffness obtained from the interactions of all mixed-mu levitator components and, in particular, that occurring between the superconducting screens and the eddy current damper sheets. The superconducting screens are shown to provide a negative damping component whilst the damper sheets provide an enhanced dynamic stiffness. A non-linear time response analysis is presented together with predictions of both dynamic and static forces, the latter showing good agreement with magnetostatic experimental results.