Abstract: The shafts of many modern rotating machines have usually been designed into supercritical flexible shafts. The vibrations induced by various perturbations during operation may cause large amplitude displacements relative to the support structure, and/or give rise to system instability, even to major accidents. An important remedy is to place an active control force in the proper location of the shaft. The stability analysis and response control of a rotor system with electromagnetic forces are investigated in this paper. The formulas of magnetic forces with respect to the displacement of the journal center and coil current are derived. The eigenfunctions to describe the dynamic characteristic of electromagnetic forces are presented to analyze the stability of the system. The minimum setting values of controller and the relationship between the locations of the assigned sensor and actuator are given by using the perturbation method and the Rouge-Hurwitz theory on condition that the stability is satisfied. The experiment of active vibration control of a rotor system of unbalance mass has been made using an olectromagnetic actuator. The results illustrate the efficiency of the present analysis and the effect of vibration reduction.

Key words: rotorsystem, electromagnetic actuator, stability, vibration control