Identification of individual rigid body modes of a system under free-free boundary condition by modal parameter estimations

摘要

This paper focuses on the problem of identifying all individual rigid body modes and their modal masses for flexible structures under the free-free boundary condition with fewer multi-location excitations than the numbers of modes. The rigid body mass matrix of the structure can he identified with both the parameters of the intertia term determined previously by a modal parameter estimation method and the information of the coordinates of measurement points. As all rigid body properties can be obtained from the mass matrix, it becomes possible to simulate the FRFs between any two measurement points including the contribution of rigid body vibration with those identified parameters. First, the theory is explained. Then, two numerical simulations and two actural identifications for a plate structure and an automotive body component are carried out in order to verify the validity of the theory.