Direct Identification Method Using Fuzzy Numbers

Abstract

The advantages of direct identification of characteristic matrices of structures are such that we can easily determine the various modal characteristics through eigenvalue analysis: those results may match automatically with the results of the curve fits in ordinary experimental modal analysis, and further, they can be used directly in numerical calculation such as that in the finite-element method. Problems in direct identification of characteristic matrices of structures lie in the accuracy of experimental data and the estimation of their errors. In this study, we allow that experimental data values themselves include errors or deviation, and for this reason, we assume that it is reasonable to deal with them as elements in fuzzy sets. Allocating a fuzzy number to each set of experimental data and extending the operation rules of fuzzy numbers, we propose a fuzzy direct identification method. The efticiency of the proposed method was demonstrated through applications to the identification of characteristic matrices of a 3-degree-of-freedom mass-spring system and a cantilever beam.