On applicability of Hilbert-Huang transform for vibration analysis of a two-member truss

The Hilbert-Huang transform (HHT) proposed for treating the time history data of nonlinear dynamic systems comprises two parts: the empirical mode decomposition and the Hilbert transform. In this study, focus is placed on the physical interpretation of the HHT results for an elastic two-member truss, for which the nonlinear behaviour can be clearly interpreted at various stages of excitation, from nearly linear, nonlinear, period-doubling, to chaotic. The instantaneous frequency of the truss is computed using the HHT or derivative-based HHT. In each case, the result obtained by the fast Fourier transform is also presented for comparison. It is concluded that the enforcement by the HHT of the data set to be symmetric with respect to the local zero mean in extracting the intrinsic mode functions may result in frequencies that are not physically meaningful. Care needs to be taken when using HHT for interpreting the frequency contents of a nonlinear structure. © 2012 Copyright Taylor and Francis Group, LLC.