Synchronous Dynamics of a Coupled Shaft/Bearing/Housing System With Auxiliary Support From a Clearance Bearing: Analysis and Experiment

Lawen, James L.; Flowers, George T.

doi:10.1115/1.2815593

Cited by 19 publications

(5 citation statements)

References 9 publications

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“…The condition for backward whirl, which may involve severe contact forces, is understood as the condition in which the rotor is in rolling contact with the TDB [22]. A number of authors have considered the dynamics of a rotor within a clearance space [27][28][29][30][31][32][33][34][35][36][37][38][39]. With respect to operational magnetic bearing systems, which is in contrast to complete delevitation, it is important to gain a full understanding of all nonlinear dynamic issues so that appropriate control action may be designed to recover contact-free levitation.…”

Section: Introduction To Magnetic Bearing Systems and Their Associatementioning

confidence: 99%

Non-smooth Hopf-type bifurcations arising from impact–friction contact events in rotating machinery

et al. 2014

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We analyse the novel dynamics arising in a nonlinear rotor dynamic system by investigating the discontinuity-induced bifurcations corresponding to collisions with the rotor housing (touchdown bearing surface interactions). The simplified Föppl/ Jeffcott rotor with clearance and mass unbalance is modelled by a two degree of freedom impact-friction oscillator, as appropriate for a rigid rotor levitated by magnetic bearings. Two types of motion observed in experiments are of interest in this paper: no contact and repeated instantaneous contact. We study how these are affected by damping and stiffness present in the system using analytical and numerical piecewisesmooth dynamical systems methods. By studying the impact map, we show that these types of motion arise at a novel non-smooth Hopf-type bifurcation from a boundary equilibrium bifurcation point for certain parameter values. A local analysis of this bifurcation point allows us a complete understanding of this behaviour in a general setting. The analysis identifies criteria for the existence of such smooth and non-smooth bifurcations, which is an essential step towards achieving reliable and robust controllers that can take compensating action.

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Section: Introduction To Magnetic Bearing Systems and Their Associatementioning

confidence: 99%

Non-smooth Hopf-type bifurcations arising from impact–friction contact events in rotating machinery

et al. 2014

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“…The auxiliary bearing parameters as required in equation (19) are lˆ10 mm and R bˆ4 4:3 mm. U nless stated otherwise, all operating parameters are the same as in section 2.5.…”

Section: Numerical Simulationsmentioning

confidence: 99%

“…F urther detailed theoretical and experimental studies on the backward whirl problem are given by Bartha [16,17]. An early paper by Wu and F lowers [18] showed the existence of bouncing rotor motions while that of Lawen and F lowers [19] focuses on the synchronous dynamics to establish system parameters that may be varied to reduce rotor vibration during auxiliary bearing contact. R ecent methods applied to the contact problem have employed the harmonic balance method [20,21] and extensive simulations including shaft pitching at the contact [22].…”

Section: Introductionmentioning

confidence: 99%

Rotor vibration with auxiliary bearing contact in magnetic bearing systems Part 1: Synchronous dynamics

Keogh

Cole

2003

Proceedings of the Institution of Mechanical Engineers, Part C:

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M agnetic bearing systems incorporate auxiliary bearings to prevent physical interaction between rotor and stator laminations. R otor/auxiliary bearing contacts may occur when a magnetic bearing still retains a full control capability. To actively return the rotor to a non-contacting state it is essential to determine the manner in which contact events affect the rotor vibration signals used for position control. An analytical procedure is used to assess the nature of rotor contact modes under idealized contacts. N on-linearities arising from contact and magnetic bearing forces are then included in simulation studies involving rigid and exible rotors to predict rotor response and evaluate rotor synchronous vibration components. An experimental exible rotor/magnetic bearing facility is also used to validate the predictions. It is shown that changes in synchronous vibration amplitude and phase induced by contact events causes existing controllers to be ineffective in attenuating rotor displacements. These ndings are used in Part 2 of the paper as a foundation for the design of new controllers that are able to recover rotor position control under a range of contact cases.

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“…present a theoretical formulation to model transient activity during rotor drop. Lawen and Flowers [8] develop and validate experimentally a model of a flexible rotor interacting with auxiliary bearings. Coupled shaft/bearing vibration modes and their influence on rotor dynamic behavior is further considered in [5].…”

Section: Detc2007-35362mentioning

confidence: 99%

Wavelet Coefficient Characteristics During Rotor/Auxiliary Bearing Contact in Active Magnetic Bearing Systems

Cade

Keogh

Şahinkaya

et al. 2007

Volume 1: 21st Biennial Conference on Mechanical Vibration and Noise, Parts A, B, and C

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Auxiliary bearings are present in active magnetic bearing systems to prevent rotor/stator contact. If rotor/bearing contact occurs, significant impact forces may arise. Furthermore, linear control strategies may become ineffective due to the non-linear dynamics introduced by the auxiliary bearing. Rotor/auxiliary bearing contact is therefore an important consideration for the continued safe operation of an active magnetic bearing system. This work utilizes the localized nature of wavelets coefficients in characterising rotor/bearing contact responses. An experimental approach is adopted using a flexible rotor/active magnetic bearing test rig. Different disturbances resulting in periodic rotor contact and rotor/bearing rub were applied using a single active magnetic bearing. Rotor displacements were measured and the radial component and associated wavelet coefficients identified from off-line data processing. Variations of the wavelet coefficients characteristics corresponding to the periodic contact and rotor/bearing rub are assessed. The choice of mother wavelet is seen to have only a small effect on wavelet coefficient values. Wavelet analysis is shown as a feasible method for identifying time-frequency characteristics of rotor/bearing contact.

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Synchronous Dynamics of a Coupled Shaft/Bearing/Housing System With Auxiliary Support From a Clearance Bearing: Analysis and Experiment

Cited by 19 publications

References 9 publications

Non-smooth Hopf-type bifurcations arising from impact–friction contact events in rotating machinery

Non-smooth Hopf-type bifurcations arising from impact–friction contact events in rotating machinery

Rotor vibration with auxiliary bearing contact in magnetic bearing systems Part 1: Synchronous dynamics

Wavelet Coefficient Characteristics During Rotor/Auxiliary Bearing Contact in Active Magnetic Bearing Systems

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