Semi-Active Foundation Stiffness Control for Rotor Resonance Avoidance

The operating speed range of large rotating systems is often limited by vibrations caused by subcritical resonances. In this paper, a semi-active control method based on control of the foundation stiffness is presented. Modification in the foundation stiffness of the rotor system results in a corresponding change in the natural frequencies. This principle is used in the developed method to choose an optimal foundation stiffness for each rotating speed of the rotor system. The presented method is validated with a rotor model based on experimental dimensions. The vibration response of the model employing the foundation stiffness optimization is evaluated in the subcritical speed region. With the optimal foundation stiffness, the subcritical resonances caused by multiple rotor bending modes can be avoided in a given speed range. The extent of the resonance-free range depends on the control range of the foundation stiffness. In the light of the presented results, the proposed semi-active foundation stiffness control can be applied to reduce the total vibration levels in rotating systems. The presented method can be applied in any rotating system where it is possible to modify the foundation stiffness during operation.