Suppression of rotor vibrations of an electric machine at the critical speed by optimal state feedback controller

This paper presents a design procedure of a modified linear quadratic controller used for active control of rotor vibrations in an electric motor. The presented method can be used for general state-feedback design to provide adequate vibration suppression for systems with similar model structure. In practice an electric motor cannot be run at its critical frequency, nor close to it due to high amplitude resonations of the rotor shaft. By implementing the new feedback controller presented in the paper, the vibrations can not only be suppressed but the motor can also be run at its critical frequency. The focus of the paper is on practical implementation and testing of a modified LQ-controller on a test motor. The tests will prove that the results achieved from the physical test machine correspond well with the ones obtained from previous simulations.