Vibration Problems in a Turbo Molecular Pump with Active Magnetic Bearings

In experimental tests of a proto-type 2000L turbo molecular pump suspended by 5-DOF AMBs, complex vibration problems had been met. They were caused by different reasons including rotor bending modes, rotor gyroscopic effects, pump blade modes and a vibration mode created by interaction of the dynamics of the rotor and the pump motor. They influenced the pump stability and had to be considered carefully in AMB controller designs to run the rotor to a target speed of 24000 rpm. Different methods were used to deal with these vibration problems. The gyroscopic effects were dealt with using cross feedback control methods. Other vibrations, including the bending mode vibrations, the pump blade vibrations and so on, were dealt with using phase shaping control methods. Experiment results concerning them were provided. With the suitable controller design and the appropriate consideration of the dynamic problems, the rotor was successfully accelerated to its target speed.