Instantaneous frequency identification of a structure based on complex wavelet transform.

The continuous complex Monet wavelet transform is performed on a time-varying response signal and corresponding wavelet ridge is extracted according to the maximum modulus of wavelet coefficient. The instantaneous frequencies are identified based on the relationship between wavelet scale and frequencies. For decreasing the influence of noise, a method based on singular value decomposition (SVD) is adopted to de-noise. As a result, a continuous complex wavelet transform- based method is presented to identify the instantaneous frequencies of a time-varying structure. The effectiveness and accuracy of the proposed method are validated via a numerical simulation of a two degree-of-freedom spring-mass-dashpots system with time-varying stiffness. Afterward, a cable structure test is set up in the laboratory where linear and sinusoidal varying tensions are respectively applied to the cable, which results in the time varying cable stiffness. The present method is further validated via measured cable response acceleration signals. It is demonstrated that the proposed method can effectively identify the instantaneous frequencies of time-varying structures, and the method is anti-noise to some extent. [ABSTRACT FROM AUTHOR]