An unbalance on a rotor causes vibration phenomena in the rotating machine. Thus balancing is an important process in manufacturing rotary machinery. Since perfect balancing is rather difficult there are often residual unbalances on the rotor. Moreover the rotor sometimes becomes unbalanced while the machine is in operation. To overcome these problems a new control method is presented for totally active magnetic bearing systems. By this method an unbalanced rotor can be suspended without unbalance vibrations by the magnetic bearing. The method is based on the theory of the output regulation with internal stability. The ways of designing the compensator are described as follows.
(1) The system is stabilized by state feedbacks.
(2) Since unbalance forces cannot be measured directly, an observer is constructed in order to estimate unbalance forces from measurable quantities: displacements and velocities of the rotor.
(3) Using the outputs of the observer the unbalance forces are cancelled by controlling electromagnetic forces of the magnetic bearing. It is shown by numerical examples that the designed system can suspend an unbalanced rotor without whirling motions which appear when the compensation is not done. Moreover the effectiveness of the compensation for unbalance is experimentally studied by an instrument with Gyro mechanism.