Applications of Sweep Frequency Rotating Force Perturbation Methodology in Rotating Machinery for Dynamic Stiffness Identification

This paper outlines the sweep frequency rotating force perturbation method for identifying the dynamic stiffness characteristics of rotor/bearing/seal systems. Emphasis is placed on nonsynchronous perturbation of rotating shafts in a sequence of constant rotative speeds. In particular, results of the identification of flexible rotor multimode parameters and identification of fluid forces in seals and bearings are given. These results, presented in the direct and quadrature dynamic stiffness formats, permit the separation of components for easy identification. Another example of the perturbation method application is the identification of the lateral–torsional coupling due to shaft anisotropy. Results of laboratory rig experiments, the identification algorithm, and data processing techniques are discussed.