Reduced model of a rotor-shaft system using modified SEREP

A modified System Equivalent Reduction Expansion Process (SEREP) is reported to reduce large linear system-equations of motion, which also include gyroscopic effect, internal and external damping. The process is employed on equations of motion written in state-space and utilizes both right and left eigenvectors of the original system unlike only the former in conventional SEREP approach. Numerical example with a finite element model representing multi-disc rotor-shaft-bearing-dynamics shows effectiveness of the process. Nice agreement of Campbell diagrams, FRF plots and unbalance response amplitude between reduced and original systems show usefulness of the reduction process.