Operational modal analysis of a high speed passenger car under ambient excitation

The crosscorrelation function between two response measurements made on an ambiently excited structure is shown to have the same form as the system's impulse response function. Therefore, standard time domain curvefitting procedures, which are typically applied to impulse response functions, can now be applied to the crosscorrelation functions to estimate the modal parameters of structures. The polyreference LeastSquares Complex Exponential (LSCE) Method with crosscorrelation functions is firstly applied to a new highspeed train with 300km/h under operational conditions and white noise excitations on vibration test stand, and are simultaneously compared to modal parameters identified by classical modal testing methods (FRF). Results of these comparisons identified by the two methods showed coherence and maximum discrepancies of 5.4 percent on modal frequencies and 9.9 percent on modal damping values. This experimental verification implies that the proposed method of analyzing ambient vibration data can be used to accurately assess the dynamic properties of structures.