Experimental mode verification (EMV) using left-hand eigenvectors

Abstract

Estimation of structural dynamic modes associated with complicated spacecraft and launch vehicle assembly modal test articles is often a challenging endeavor. The mathematical process of modal parameter estimation, applied to measured FRF arrays, yields actual and artificial “noise” modes. Left-hand eigenvectors, estimated as part of the SFD modal identification technique, are used to compute SDOF modal FRFs from (a) the measured FRF array and (b) the estimated “effective” dynamic system. Both graphical displays of candidate SDOF modal FRFs and a modal “coherence” metric provide objective means of separating actual, credible system modes from artificial “noise” modes. Evaluation of modal test data for a Space Launch System component demonstrates the value of the new Experimental Mode Verification (EMV) technique.