System Identification of Structures with Severe Closely Spaced Modes Using Parametric Estimation Algorithms Based on Complex Mode Indicator Function with Singular Value Decomposition

The modal-interference phenomenon usually makes difficulty of parametric estimation, especially for some structural systems with severe modal interference caused from close or even repeated modes. The existence of severe modal interference will degrade the effectiveness of system identification, and may lead to the problem of insufficient model order due to the existence of repeated modes. Multiple input/multiple output modal estimation is therefore usually conducted effectively to meet the sufficient number of measurement channels. In this paper, the Complex Mode Indicator Function is introduced to estimate the number of significant modes of a structure with severe modal interference, and then the singular value decomposition (SVD) is employed to parametric estimation of the major modes of a structural system without additionally evaluating enhanced frequency response function. Numerical simulations and experimental validation of a practical rectangular steel plate confirm the effectiveness of the presented method for parametric estimation of systems with severe closely spaced modes under noisy conditions.