Identification for Modal Parameters Based on Improved Random Decrement Technique and Wavelet Transform

Abstract:

This paper presents a new statistical identification method for structural modal parameters based on the improved random decrement technique and wavelet transform. The improved random decrement technique is used to deal with zero mean non stationary signals directly for free decay responses. The wavelet transform is applied to decoupling dense frequency and low damping system because of its advantages in time frequency domain. The bootstrap procedure is employed to evaluate and decrease the uncertainty of the identification results. The reliability of the proposed method is validated by a four degree freedom numerical example. Compared with the traditional time domain method and the wavelet transform only method, the presented method has higher estimation accuracy, especially for damping ratios. Subsequent validation results for noise resistance show that the presented method is able to identify the modal parameters stably and precisely at the presence of 15dB measuring noise, which is applicable for structural modal parameter identification under environmental excitation.