Using a De-Convolution Window for Operating Modal Analysis

Operating Modal Analysis (OMA) has been applied in a number of cases recently for finding the experimental modal parameters from structures when their excitation forces cannot be measured. Without force measurement, a classical Experimental Modal Analysis (EMA), which relies on the application of modal parameter estimation, or curve fitting methods to a set of Frequency Response Function (FRF) measurements, cannot be performed. In this paper, we show that the application of a de-convolution window to cross power spectrum data yields the effective recovery of the FRFs involving each vibration response signal. A set of recovered FRFs can then be curve fit using classical FRF-based curve fitting methods to identify the experimental modal parameters of the structure. Use of the de-convolution window is illustrated in an example that uses a FRF matrix model to calculate structural responses to simulate a multireference OMA.