Identification of Nonlinear Normal Modes of Engineering Structures under Broadband Forcing

TL;DR

This paper presents a novel two-step method combining system identification and numerical continuation to experimentally extract nonlinear normal modes of structures under broadband forcing, demonstrated on a nonlinear cantilever beam.

Contribution

It introduces an integrated approach for experimental NNM extraction that combines data-driven modeling with continuation techniques, advancing nonlinear structural analysis.

Findings

Successfully extracted NNMs from noisy synthetic data

Validated method on a cantilever beam with nonlinear behavior

Demonstrated robustness of the approach under broadband forcing

Abstract

The objective of the present paper is to develop a two-step methodology integrating system identification and numerical continuation for the experimental extraction of nonlinear normal modes (NNMs) under broadband forcing. The first step processes acquired input and output data to derive an experimental state-space model of the structure. The second step converts this state-space model into a model in modal space from which NNMs are computed using shooting and pseudo-arclength continuation. The method is demonstrated using noisy synthetic data simulated on a cantilever beam with a hardening-softening nonlinearity at its free end.