Experimental modal analysis of a beam travelled by a moving mass using Hilbert Vibration Decomposition

In this paper the problem of modal identification of time-varying system is investigated. To do so, a technique based on the sifting process of the Hilbert Vibration Decomposition (HVD) method is presented. The key idea is to estimate the instantaneous frequency of the dominant mode, to extract its corresponding component by demodulation of the recorded signals and then to iterate with the subsequent dominant mode. In the case of multiple recorded signals, a source separation method is used as a preprocessing step to facilitate the identification of the instantaneous frequency for the following demodulation step.
To illustrate the method, an experimental set-up consisting in a beam travelled by a non negligible mass is considered. The whole structure is randomly excited during the travel of the mass and some responses on the beam are recorded.