Modal Parameter Extraction Using Natural Excitation Response Data

The use of natural excitation response data for the extraction of modal parameters has been an alluring idea for many years, The primary reason is that it offers the real world inputs (both spatial and temporal) and the associated responses of the system without the cost of a complex excitation system. The use of NExT allows for a linear representation of the system at operating levels, which is ideal for predictive linear simulation. The NExT parameter estimation methods have relied on using standard modal parameter extraction routines that do not exploit the special model form of NExT data. A parameter estimation method is developed here that is consistent with the form, thereby providing a more robust estimator in the presence of noise. This paper presents the basic methods used in NExT as well as some of the critical issues when using NExT