Vibration and Control in Outer Rotor Type Magnetic Bearings

The magnetic bearings described here has been developed for high speed rotating machinery. The manufactured experimental model Is 4-axls-active type with simple structure. Since the model is so called outer-rotor type, resonance frequency of the rotor could set higher than rotating frequency, and only first resonance frequency of the stator shaft is in the rotating region. In this paper, we describe the analysis and experimental results to obtain stable high speed rotation. Firstly, stability of the gyroscopic motion of rigid mode is examined at low speed rotation. Subsequently. influence of flexibility of the stator shaft on stability is discussed. Then we indicate that nonlinearity of the power amplifier plays an important role in stabilIty of the system. Finally, a suppression method usIng notch-fillers and lnler-axis cross coupling feedback at relatIvely high speed rotation is discussed.