Rotordynamic Behavior and Rigid Mode Vibration Control by Hybrid Foil-Magnetic Bearing System

In a hybrid foil-magnetic bearing (HFMB), an air foil bearing (AFB) serve as auxiliary bearings for an active magnetic bearing (AMB). This enables design simplification and weight reduction, and it can reduce the energy consumption of the AMB. Therefore, an HFMB has higher efficiency and reliability. This study conducts vibration control tests of an HFMB at increasing rotor speeds for various AMB control parameters. AMB control parameters are experimentally determined for achieving an appropriate load distribution between the AMB and the AFB. Furthermore, to minimize the vibration and energy consumption, the ON/OFF period control of the AMB is adjusted properly according to the operating speed. Accordingly, the HFMB can afford the high load capacity of the AFB at high speed as well as the high static stiffness to prevent initial rubbing and the control capability of the AMB to suppress excessive vibration. Therefore, the HFMB improves the performance of rotating machinery significantly in terms of range of operation and reliability. In addition, the effects of the load distribution between the AMB and the AFB are investigated by changing the control characteristics to produce different stiffness and damping effects. The HFMB for a high-speed rotor is experimentally optimized by altering the load distribution of the two bearings in terms of rigid mode vibration.