Computer simulation of structure experimental mode based on virtual instrument

Identification of modal parameters using orthogonal polynomials possesses high precision. In the paper, a new approach is proposed in using virtual instrument for identification of the natural characteristics which are the mode frequency, mode damping and mode shapes of a mechanical structure. A multiple—input modal identification method in the frequency domain is discussed The frequency response function(FRF)is expressed as a rational fraction formulation with matrix coefficients. The Forsythe orthogonal polynomial is exploited to reduce the ill-conditioning of the equations and to decouple the system matrix. Taking use of the eigenvalue decomposition and singular value decomposition the poles and residues of the system are solved. It combines the developed virtual instrument software “LabVIEW” with the software Visual C++ for modal analysis, and makes program using LabVIEW for controlling the data acquisition card to generate a file with a fixed data format and applies this file to complete the experiment of analysis making program using Visual C++. The experimental results for different structures have certified the availability of the approach.