13. A “Local Solve” Method for Extracting Modal Parameters from Inconsistent Data

A local solve method will be presented for extracting modal parameters from inconsistent data. By definition global parameter estimation methods cannot handle inconsistent Frequency Response Function (FRF) data (frequency shifts, non-linearity’s, etc.) and in practice it is very difficult to select appropriate poles from the stability or consistency diagrams presented in commercially available modal parameter estimation methods. The typical way to resolve this issue is to employ measurement techniques that acquire all FRF’s simultaneously, requiring shakers, numerous accelerometers and a large channel count acquisition system; or performing a Roving hammer, Multiple Reference Impact Test (MRIT). The reality is that sometimes FRF data is not acquired in a consistent manner. This paper presents a “local solve” method that performs a global solve on individual or groups of consistent FRF’s and combines the end result into a set of global modal parameters.