FREQUENCY-DOMAIN DIRECT PARAMETER-IDENTIFICATION FOR MODAL-ANALYSIS - STATE-SPACE FORMULATION

This paper outlines the theoretical development of a modal identification technique for the dynamic behaviour of linear time-invariant systems. Using a state space formulation for the equations of motion for a mechanical structure, an algorithm is developed to identify its state transition matrix from measured multiple input/multiple output relations (frequency response functions). From the identified matrix quantities, it is possible to derive a modal model of natural frequencies, damping values, mode shapes and modal participation factors. Aspects of data reduction via singular value analysis are discussed to extract valid state variables from the entire set of response stations. Emphasis is put on the application of this frequency domain direct parameter identification technique for the analysis of non-uniformly sampled frequency response functions, as generated for example when automated stepped-sine excitation is applied for modal testing of mechanical structures. © 1990.