Performance Assessment of a Multi-Frequency Controller Applied to a Flexible Rotor Magnetic Bearing System - Contact Dynamics

Reference:

Abulrub, A. H. G., Sahinkaya, M. N., Burrows, C. R. and Keogh, P. S., 2008. Performance Assessment of a Multi-Frequency Controller Applied to a Flexible Rotor Magnetic Bearing System - Contact Dynamics. In: Ulbrich, H. and Ginzinger, L., eds. 9th International Conference on Motion and Vibration Control, 2008-09-15 - 2008-09-18, Munich.

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Official URL:

http://dx.doi.org/10.1007/978-1-4020-9438-5_2

Abstract

Vibrations associated with external disturbances and rotor faults, such as cracks, usually exhibit themselves as harmonic components of the synchronous frequency. The essence of the multi-frequency form of the synchronous recursive open loop adaptive controller (ROLAC) is that it can minimise a number of vibration components simultaneously, for example, synchronous rotor vibration at frequency Ω, its harmonics and sub-harmonics within any defined range. This requires on-line identification of the speed dependent partial receptance matrix by using a multifrequency test signal incorporating all of the pertinent harmonic components. The question arises: What is the degradation in performance if the rotor comes into contact with its retainer bearing? This may arise when a magnetically levitated rotor is installed on a movable base frame, for example on board a ship or an aircraft. A simulation study is described to examine this question. It comprises a flexible rotor supported by two active magnetic bearings. Eight displacement transducers are positioned along the rotor. A local PID controller is provided for each axis of the magnetic bearings to ensure stability and alignment of the rotor at a central position. An outer ROLAC loop is incorporated at each bearing to control the vibrations at discrete frequencies of 0.5Ω, Ω, 2Ω and 3Ω. In addition, a multi-frequency disturbance was applied to the rotor causing contact with its retainer bearing. The performance of the multi-frequency ROLAC is assessed in preventing contact, or recovering the rotor position if contact occurs.

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