Modal parameter identification of a rotating large umbrella truss structure using digital image correlation

Abstract

An effective experimental identification of modal parameters of a rotating large umbrella truss structure has been developed which uses Digital Image Correlation (DIC) technique in a framework that integrates with Improved Empirical Wavelet Transform (IEWT) and Random Decrement Technique. In order to offset gravity effect in the ground experiment, an air-bearing-based supporting device is designed to allow a large umbrella truss structure to have a frictionless rotation about its mass center. Burg's algorithm is used to calculate the Standardized Autoregressive power spectrums, according to the full-field displacement of the rotating umbrella truss structure captured by DIC. Using the Standardized Autoregressive power spectrums, the natural frequencies of rotating umbrella truss structure are identified, while the corresponding damping ratios and mode shapes are determined via the nonlinear curve fitting method. Finally, vibratory modal analysis of the rotating large umbrella truss structure was performed at different rotating speeds. The presented technique is anticipated to provide an effective approach for identification of modal parameters of large space structures in practical applications.