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

Abstract

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.

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

“…The mechanical model, illustrated in figure 1, is adopted from [22]. It comprises a rotor, with a disc cross section of radius R, spinning at a high constant speed, Ω > 0, inside a fixed, circular TDB.…”

“…Then the rotor's motion can be approximated by a linear spring-damper system with stiffness k and damping c [22]. For real machines the integral (I) gain would be typically set at a level that gives rise to a dynamic mode having a very long time constant.…”

“…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].…”

The study of non-smooth dynamics of a class of multi-degree-of-freedom vibro-impact system with clearance

“…Karin Mora [4] analysed the novel dynamics arising in a nonlinear rotor dynamic system by investigating the discontinuity-induced bifurcations corresponding to collisions with the rotor housing. Keogh & Cole [5] show that a rotor-stator system with damping and friction can exhibit various forms of stable and unstable synchronous single impact limit cycles. Similar discontinuity-induced Hopf bifurcations, exhibiting a bifurcation of a non-impacting equilibrium to a limit cycle with impact, have been observed in planar piecewise smooth continuous systems [6] with sliding [7] and with biological applications [8].…”

Vibration reduction in a hollow-shaft rotor using flexibly-mounted internal-stator magnetic bearings

“…In subsequent work, various authors have addressed specific tasks and applications relating to the use of magnetic bearings: Clark et al (2004) summarises work that has been done towards the use of AMBs in gas turbine engines; self-sensing (sensorless) techniques have been explored by Vischer and Bleuler (1993) , and Noh and Maslen (1997); control of rotor/stator contact events have been addressed by Keogh et al (Cole and Keogh, 2003;Keogh and Cole, 2003;Keogh et al, 2004); Komori et al consider systems incorporating superconducting magnetic bearings (Komori and Shiraishi, 2003;Komori et al, 1996Komori et al, , 1998. Lusty and Keogh, Mechanical Engineering Journal, Vol.4, No.5 (2017) [DOI: 10.1299/mej.17-00008] However, a commonality among the vast majority of this work is the basic design and construction of the magnetic bearings, and the topology of the rotor system.…”