Abstract
Methods for nonlinear system identification of structures generally require input-output measured data to estimate the nonlinear model, as a consequence of the noninvariance of the FRFs in nonlinear systems. However, providing a continuous forcing input to the structure may be difficult or impracticable in some situations, while it may be much easier to only measure the output. This paper deals with the identification of nonlinear mechanical vibrations using output-only free-decay data. The presented method is based on the nonlinear subspace identification (NSI) technique combined with a mass-change scheme, in order to extract both the nonlinear state-space model and the underlying linear system. The technique is tested first on a numerical nonlinear system and subsequently on experimental measurements of a multi-degree-of-freedom system comprising a localized nonlinearity.
Highlights
Understanding the dynamical behavior of mechanical structures exhibiting nonlinearities has become of great interest in the last decades, due to the continual interest in improving design and performances
Providing a continuous forcing input to the structure may be difficult or impracticable in some situations, while it may be much easier to only measure the output. is paper deals with the identification of nonlinear mechanical vibrations using output-only free-decay data. e presented method is based on the nonlinear subspace identification (NSI) technique combined with a mass-change scheme, in order to extract both the nonlinear state-space model and the underlying linear system. e technique is tested first on a numerical nonlinear system and subsequently on experimental measurements of a multi-degree-of-freedom system comprising a localized nonlinearity
When experimental data are considered, a common way to gather a reliable model is via system identification. is task can be challenging when the system is behaving nonlinearly due to the breaking of the basic principles of linear modal analysis
Summary
Understanding the dynamical behavior of mechanical structures exhibiting nonlinearities has become of great interest in the last decades, due to the continual interest in improving design and performances. A method for performing output-only nonlinear system identification from free-decay measurements is presented and validated. In its original form, NSI is an input-output identification algorithm relying on a nonlinear state-space representation of the system, obtained by considering the nonlinear terms as unmeasured internal feedbacks to the so-called underlying linear system [10]. When output-only free-decay measurements are considered, NSI in its original form cannot be used to fully estimate the nonlinear model. It is still possible to estimate the modal parameters of the underlying linear system, but a quantification of the nonlinear contribution is not available [15]. The identification of nonlinear structures with unmeasured (stochastic) inputs still remains an unreached goal for the research community [2], and the method proposed in this study can be considered as a first step towards this direction. e methodology is first tested on a numerical dataset of a multi-degree-of-freedom system comprising a polynomial nonlinearity and on an experimental test bench of a scaled nonlinear multistory building
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
