System Identification of Structures with Modal Interference

Abstract

Previous studies show that when a system has repeated modes in frequency domain, the multiple-input and multiple-output (MIMO) concept can be applied to effectively identify the modal parameters. In this study, the MIMO concept is extended to the time domain for system identification of systems with modal interference. When performing a modal analysis of a structural system with close modes or high damping, the results of identification may be poor due to modal interference, and the estimation of system order is important to the effectiveness of modal identification. By introducing the concept of the singular value decomposition (SVD) in Eigensystem Realization Algorithm (ERA), and simplifying the identification process of ERA, the system order will be estimated effectively even for a system having close (even repeated) modes. In addition, the correlation matrix is also used to perform SVD, and then directly identify modal parameters, i.e., omitting the additional process of constructing the generalized Hankel matrix, which provides a more efficient method of identification of modal parameter. Also, in this paper, the SVD algorithm is introduced to the identification process of Ibrahim Time-Domain Method. The order of system matrix is efficiently determined, and the modal identification of a system with close modes through the ITD method can then be well implemented.