Modern spectral estimation techniques for structural health monitoring

The authors present results for the application of a novel family of signal processing tools, known as modern spectral estimation (MSE) techniques, to multi-channel accelerometer data collected in a structural test experiment. MSE techniques hold the promise of providing a fully automatable means of extracting modal parameter estimates (i.e., eigenfrequencies and mode shape vectors) from time-series accelerometer data. In analyses performed on experimental data acquired from a vibrating test article, the effectiveness of the approach was confirmed insofar as it demonstrated a strong correspondence between MSE-calculated response frequencies and power spectra peaks calculated using a discrete Fourier transform (DFT). All of the major peaks that appear in the DFT power spectra are identified and their widths characterized accurately. Tracking of MSE values over time can potentially provide indication of small and subtle shifts in modal parameter values, and thereby early warning of structural damage. These methods lend themselves to nonintrusive, in situ monitoring based on natural excitation and can be used in forward-fit (e.g., composite structures), as well as in retrofit, applications.