Direct Identification Method Using Fuzzy Numbers

Advantages of direct identification of characteristic matrices of structures follow that we can easily determine the various modal characteristics through eigenvalue analysis, and those results may match automatically with the results of the curve fit of all point inputs and all point outputs in ordinary experimental modal analysis techniques, and also, they can be directly used in numerical calculation such as the finite-element method. Problems in direct identification of characteristic matrices of structures lie in the accuracies of experimental data and estimation of their errors. In this study, we allow that experimental data themselves include errors, and for that reason, we assumed that it is rather reasonable to take them as ‘fuzzy’ sets. Setting a fuzzy number to each set of experimental data and modifying the calculation rules of fuzzy numbers, we propose a fuzzy direct identification method. The efficiency of the proposed method was shown through an application to the identification of characteristic matrices of a 3-degree-of-freedom mass spring system and a cantilever beam.