Rotordynamic Behavior and Performance of Controllable Hybrid Foil-Magnetic Bearing

Abstract

This paper presents a state space model validation and means of vibration suppression for a rigid rotor supported by hybrid foil-magnetic bearings (HFMBs), using an additional PD controller. The main difficulty related to reducing the vibration of a rigid rotor using an HFMB is the realization of a controller that can minimize resonance without rigid modes. To solve this problem, we developed a state space scheme for system modeling and controller design. First, a rigid rotor supported by air foil bearings is linearized with a magnetic bearing and PD controller, to give a new stable rotor-bearing system. Then, we propose a model validation procedure that uses analytical open-loop imbalance responses to obtain an accurate model of the HFMB rigid-rotor system. After that, a rotor behavior simulation with a PD controller under a range of conditions was designed so as to suppress the rigid mode of the stable rotor-bearing system. A comparison of the measured and simulated results revealed poor controllability and vibration control in the rigid modes. Simulation with step-by-step disturbances, as well as the measured results for the imbalance up to 10,000 rpm, verified the efficacy of the HFMB scheme.