Structural Dynamic System Reconstruction Method for Vibrating Structures

Abstract

To determine the natural frequencies and damping ratios of composite laminated plates, we present an efficient modal parameter estimation technique by developing a residual spectrum based structural dynamic system reconstruction. The modal parameters can be estimated from poles and residues of the system transfer functions derived from the state space system matrices. However, for modal parameter estimation of multivariable and higher order structural systems over broad frequency bands, this noniterative algorithm gives high accuracy in determining the natural frequencies and damping ratios. It is numerically well-behaved unlike iterative frequency-response-function (FRF) curve-fitting methods. We also discuss necessary conditions for convergence in Hankel norm and the error bounds of the approximated transfer function for the IDFT-based reconstruction system. From vibration tests on cross-ply and angle-ply composite laminates, the natural frequencies and damping ratios can be identified from the eigenvalues of the structural dynamic system matrix derived by the reconstruction method from the experimental frequency response functions. These results are compared with those of finite-element analysis and single-degree-of-freedom curve-fitting.