Controller design for a rubbing rotor

A new approach to control a rubbing rotor by applying an active auxiliary bearing is developed. The auxiliary bearing is attached to the foundation via two unidirectional actuators. The control force is applied indirectly using the active auxiliary bearing only in case of rubbing. A framework for the development of a feedback controller for an active auxiliary bearing is presented. The theory of a robust two-phase control strategy which guarantees a smooth transition from free rotor motion to the state of full annular rub is presented. A simulation environment for the elastic rotor and the auxiliary bearing including the non-smooth nonlinear dynamics of the rubbing contact is used to develop the feedback controller. Experimental studies have been carried out at a rotor test rig. Various experiments show the outstanding success of the strategy. In case of rubbing, the contact forces are reduced up to 90%.