Experimental Verification of a Test-Based Hybrid Component Mode Synthesis Approach

Abstract

A new approach to component mode synthesis in which the characteristics of individual components are determined experimentally through modal and static tests is described. The component characteristics used in the technique are the mass matrix, rigid-support normal modes and frequencies, residual flexibility attachment modes, and static constraint modes. All component characteristics, except the mass matrix, are obtained through tests. A novelty of the approach is that it allows determination of the test-based characteristics by testing the components when they are attached to supports of arbitrary stiffness. This procedure obviates the need for providing fully rigid or highly flexible supports, as is normally done. In addition, reaction forces at the supports need not be measured during modal testing. The approach has considerable potential for application in testing of large flexible space structures. The theoretical formulation is summarized. The effectiveness of the procedure is experimentally verified by obtaining estimates of the modal parameters of a free-free beam and a free-free grid structure. It is found that the system parameters obtained from the proposed approach exhibit significant improvement in accuracy when a certain minimum number of residual flexibility terms are included in parameter estimation. This is particularly true when the structure being tested is complex.