DESTABILIZATION OF FORWARD RUB IN ROTOR MAGNETIC BEARING SYSTEMS USING ACTIVELY CONTROLLED AUXILIARY BEARINGS

During fault conditions, rotor displacements in magnetic bearing systems may potentially exceed safety/operating lim-its. Hence it is a common design feature to incorporate auxil-iary bearings adjacent to the magnetic bearings for the preven-tion of rotor/stator contact. During fault conditions the rotor may come into contact with the auxiliary bearings, which may lead to continuous rub type orbit responses. In particular, for-ward rub responses may become persistent. This paper advances the methodology by considering an actively controlled auxiliary bearing system. An open-loop control strategy is adopted to pro-vide auxiliary bearing displacements that destabilize established forward rub orbit responses. A theoretical approach is under-taken to identify auxiliary bearing motion limits at which forward rub responses become unstable. Experimental validation is the