On the use of dispersion analysis for model assessment in structural identification
Journal
Journal of Vibration and Control
Date Issued
November 2013
Author(s)
Abstract
One of the most important issues faced in parametric time-domain identification and subsequent experimental/operational modal analysis is the correct estimation of model order, which in turn determines the number of structural vibration modes. The aim of this study is to provide a quantitative and physically meaningful framework for model order assessment that is characterized by global applicability, in the sense of implementation in both state-space and transfer function model representations. To this end and under the assumption of stationary wideband excitation, a novel dispersion analysis scheme is proposed for the quantification of every mode's relative importance to the total stochastic response, which is based on a modal decomposition of the covariance matrix. Subsequently, after defining the modal dispersion matrix, a corresponding metric is introduced and used either as a stand alone tool for model order assessment, or as an extension of existing tools, such as stabilization diagrams. The method is validated through both simulated (NASA Mini-Mast truss) and experimental (suspended steel subframe flexible structure) identification problems, for which a subspace and a prediction-error estimation method are utilized and compared under the proposed quantitative indices. Moreover, performance comparisons with other energy-based metrics are also reported. The results indicate that the proposed method can be effectively used in parametric time-domain structural identification, for both order assessment and comparison of diverse model-based estimation methods.
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