Vibration Control for an Overhung Rotor System using Actively Flexible Bearing Pedestal.

This paper describes an active vibration control system to effectively reduce the unbalanced vibration of rotating machinery with an overhung rotor. The overhung rotor is supported by a flexible bearing pedestal installed in four pairs of U-shaped electromagnets. The displacement signal measured at a flexible pedestal is fed back to the magnet. The pairs of upper and lower, and right and left electromagnets are independently controlled in the vertical and the horizontal directions. The PD control is performed in the system and the electromagnetic actuator can apply active control forces, that is, the equivalent spring force and the equivalent damping one in proportion to the PD feed back gain, to the flexible bearing pedestal to reduce the vibration of the overhung rotor indirectly. In the analysis, we confirm that there are the optimum values of the PD-controller gains to reduce the vibration of the overhung rotor. In order to make certain of our analytical results, we perform some experiments for the simply modeled test equipment with an overhung rotor. The suppression effect of the controllable flexible bearing in electromagnets is experimentally confirmed to unbalance vibrations of overhung rotor.