Vibrations in rotating system are considered as one of the major operating problems since they have adverse effects on the performance of rotating system, which result in operating life reduction.
In this research, the active control of vibration, as a response to mass unbalance, in a rigid rotor symmetrically supported by an oil film bearing is considered.
A model of rigid rotor is considered in this study, in which the unbalance mass is positioned out of the plane of the geometrical center of the system.
For the cases studied, the active control of system vibration was achieved by the Application of two techniques, namely, pole placement and optimal control techniques, the system dynamics is represented by mathematical models and the system is simulated by a digital computer using Matlab programs.
The results obtained showed a high reduction in vibration amplitude, This reduction was more than 80 % and in some situations it raises to more than 90 %.
Key words: Rotor vibration, rotor bearing system, Active vibration control.