Strategies for Non-Linear System Identification in Base Excited Structure

Abstract

The traditional nonlinear parameter identification techniques described in the existing literature required force and response information at all degrees of freedom. For cases, where the excitation comes from base input, those methods cannot be applied directly unless the measurement is made in all degrees of freedom. The emphasis of this research is upon nonlinear identification of the large, multi-mode, lightly damped, continuous system, where the excitation comes from the moving base. The emphasis is to identify the nonlinear model in parametric forms, where the linear modal testing method is not sufficient to describe the dynamics of the structure. For this reason, a method suitable for the identification of a model based on improved hybrid modal space and modal space is considered. The proposed methodology shows the extraction process of pseudo force projected at the measured degrees of freedom. An experiment is performed to validate the proposed method in a cantilever beam. Nonlinear parameter selections are done through multilinear regression in a modal domain. A significant cubic stiffness nonlinearity is found in the first mode. The cross-coupling stiffness terms are found to be insignificant during regression analysis.