Efficient and robust rub control with an active auxiliary bearing

In this contribution, a new approach to control a rubbing rotor by applying an active auxiliary bearing is presented. The auxiliary bearing is attached to the foundation via two unidirectional actuators. The control force is applied indirectly using the auxiliary bearing, only in case of rotor rubbing. During a normal operation state, the feedback control does not interfere with the rotor system at all. A robust control system has been developed which significantly reduces the intensity of rubbing by stabilizing the rotor system and assuring an optimal rubbing state in case of a too large rotor amplitude. The two-phase control strategy guarantees a smooth transition from free rotor motion to the state of synchronous full annular rub. A test rig has been developed to experimentally verify the control system. Various experiments show the success of the control strategy. In case of rubbing, the contact forces are reduced up to 80 per cent, which results in significantly lower loads. At the same time, the rotor deflection is decreased too. For industrial applications, the activation of the control system can be operated fully automatically. The high efficiency of the control algorithm allows an implementation on microcontrollers. The developed control of the auxiliary bearing reduces the load and the noise of the system during rotor rubbing significantly.