IDENTIFICATION OF INSTANTANEOUS FREQUENCIES OF TIME-VARYING STRUCTURES BASED ON WAVELET RIDGES

This paper presents an application of wavelet analysis for identification of instantaneous frequency of a time-varying structure. A method of extracting signal wavelet ridge is presented, then the instantaneous frequencies of signal are obtained according to the relation between wavelet scale and frequencies. The effectiveness and accuracy of the addressed method are validated via a numerical simulation of a two degree-of-freedom spring-mass-dashpot system with time-varying stiffness. Thereafter, the proposed method is further verified by the experimental data from a cable structure loaded varying tension that is tested in the laboratory. It is demonstrated that the proposed method can effectively identify the time-varying instantaneous frequencies. The result can be used to monitor the variation of time-varying structures and evaluate the structural health condition.