To attenuate synchronous disturbances in magnetic bearing systems, a number of approaches have been used, including both adaptive feed-forward and feedback approaches. In practice it is generally preferred to use feed-forward techniques as they have less effect on system stability. One method of feed-forward disturbance attenuation that has been proposed is the application of adaptive filtering techniques to minimize the magnitude of the magnetic bearing system error signal. This will be referred to as "indirect" method for synchronous disturbance attenuation.