An Active Auxiliary Bearing Control Strategy to Reduce the Onset of Asynchronous Periodic Contact Modes in Rotor/Magnetic Bearing Systems

Abstract

To prevent rotor/stator contact in a rotor/magnetic bearing system, auxiliary bearings may be located along the shaft and at the magnetic bearings. Rotor responses after a contact event may include periodic trapped modes where repeated contact may lead to highly localized thermal stresses. This paper considers an active auxiliary bearing system with a control strategy designed to limit the trapped contact modes in a rotor/magnetic bearing system that are induced by rotor unbalance. The controller is evaluated from a system model and its responses to short duration contact events. An active auxiliary bearing model is introduced to the system where the dynamic response of the bearing is dependent on the controller. From a harmonic decomposition of rotor/bearing contact, dynamic controllers are sought, which limit the numbers of possible periodic solutions for a given rotor unbalance and operating speed. A case study is performed considering a simple two degree of freedom system with passive and active auxiliary bearings. Recovery of a rotor trapped in an asynchronous contact mode is shown with variation of the auxiliary bearing controller parameters.

4A16 Model-Based Condition Monitoring of an Auxiliary Bearing following Contact Events

“…is a compromise between too much stiffening for lower orders and too much support for higher orders with the coefficients of w 0 being constrained by the constant torsion characteristics of (21). In combination, rigid and elastic body motions are decoupled and a compact form of the equations of motion with appropriate approximation not depending on the boundary conditions is available for evaluation.…”

“…To verify the developed concept, a test rig, which has been developed at the University of Bath (21) , is used.…”

Impulsive Control of the Rotor-Stator Rub Based on Phase Characteristic

“…Ginzinger and Ulbrich [6] developed a two-phase control strategy to stabilize the rotor system in case of rub and effectively avoid backward whirling. References [7,8] considered the concept of using an active auxiliary bearing operating with an active magnetic bearing system.…”