Experimental assessment of touchdown bearing contact forces in magnetic bearing systems

Abstract

Active Magnetic Bearings (AMBs) have many advantages such as allowing near frictionless rotation and high rotational speeds. Touchdown bearings (TDBs) are a requirement in AMBs to prevent system damage under certain conditions, such as high loads, transient faults, or external disturbances. These conditions may lead to rotor/TDB contact. The AMBs may have the capability to restore contact-free levitation of the rotor, though this will require an understanding of the TDB contact dynamics, together with appropriate control strategies. The experimental evaluation of a TDB dynamic contact force measurement system, in which strain gauge sensors are employed, is described in this paper. The relationships between TDB contact force dynamics and induced AMB forces are derived. Assessment of contact forces under varying amplitudes and frequencies applied by an AMB is presented. The data generated can be used to validate dynamic system models, and aid the design of control action to minimise or eliminate contact forces.