Nonlinearity and non-stationarity analysis of dynamic response of vehicle-track coupling system enhanced by Huang transform

A method is proposed to analysis the nonlinearity and non-stationarity of dynamic response of high speed vehicle-track coupling system, to understand the properties of signal and its underlying physical meaning. First, a space coupling model of high speed vehicle-track system is built according to the theory of coupling dynamics of vehicle-track system. Then, the dynamic response of vehicle-track system is processed by Ensemble Empirical Mode Decomposition (EEMD) to generate the intrinsic mode functions (IMFs). Next, the “Direct Quadrature” (DQ) method is used to calculate the local instantaneous frequency and instantaneous amplitude of the IMFs, the generalized zero-crossing method and the full wave zero-crossing method are applied to calculate the mean local frequency of the IMFs. Finally, the index and degree of nonlinearity and non-stationarity based on intra-wave frequency modulation (the deviation of the instantaneous frequency from the generalized zero-crossing frequency) and inter-wave frequency modulation (the deviation of the instantaneous frequency from the full wave zero-crossing frequency), are defined to quantify the nonlinearity and non-stationarity of dynamic response. The usefulness and capability of the proposed method are displayed through two cases, which are considered general enough to be the representatives of nonlinear and non-stationary dynamic response of vehicle-track coupling system.