Vibration control of flexible rotor by inclination control magnetic bearings with axial self-bearing motor

An inclination control method has been developed to stabilize a flexible rotor on magnetic bearings that operates over several critical bending speeds. It is desired to increase the rotating speed of the centrifuge which is supported by magnetic bearings on both ends of the rotor. Each magnetic bearing Is composed of a pair of hybrid-type magnetic bearings and can control the inclination as well as the position of the rotor. The central position and the inclination of the rotor are calculated by the sum and difference of the measured displacements. These two quantities are supplied to the individual proportional and derivative controllers to obtain the actuating signals. The central position is controlled to provide sufficient stiffness to support the rotor while the inclination control capability is used to obtain adequate damping for the bending mode of the rotor. The control approach is tested on a rotor with three midspan disks to reduce the bending resonances with complete noncontact levitation. A high rotating speed of 6300 r/min was achieved, which is above the fifth bending critical speed.