...P. S. Keogh; M. O. T. Cole; M. N. Sahinkaya; C. R. Burrows During the normal operation of rotor/magnetic bearing systems, contacts with auxiliary bearings or bushes are avoided. However, auxiliary bearings are required under abnormal conditions and in malfunction situations to prevent contact...

.... Complex rotor dynamics may involve contact with more than one auxiliary bearing or bush. Application of appropriate rotating forces to the rotor through a magnetic bearing is also shown to induce similar contact dynamics. Thus, an alternative procedure for assessing the nonlinear rotor dynamic behavior...