Frequency modulated empirical mode decomposition method for the identification of instantaneous modal parameters of aeroelastic systems

Instantaneous modal parameters are effective indicators of nonlinearity in an aeroelastic system. The Identification of them requires reliable algorithms. A frequency modulated empirical mode decomposition (FM-EMD) method is proposed in this paper to track the variations in the modal parameters of a multi-DOF bridge–air system. The proposed method is a lifted version of the traditional EMD method. It overcomes one of the major shortcomings of its traditional version, i.e. the inability to separate closely spaced modes. Numerical verification was provided to show the effectiveness of the FM-EMD method. Wind tunnel testing data of a partially streamlined box girder sectional model of a suspension bridge was processed subsequently with the proposed method. Instantaneous frequencies and damping ratios of the aeroelastic system during the free decay vibration were realized. Nonlinearity in the transient aeroelastic vibration was identified.