Indirect measurement of multiple excitation force spectra by FRF matrix inversion: Influence of errors in statistical estimates of FRFs and response spectra

摘要

In this paper, the indirect measurement of multiple broad band force spectra by FRF matrix inversion, using popular FFT-based spectral analysis techniques, is considered. Since inverse force measurements are often met with same mistrust because of their sensitivity to small, more or less unavoidable errors in measured data, it is attempted to clarify various possible error mechanisms. To this end, the influence of statistical errors in the estimation of FRFs and response spectra on inversely determined force spectra was investigated. Based on the knowledge of main characteristics of each of the potential error types, models were derived to characterise the propagation to, and the distribution over, computed force spectra. In contrast to work reported on in the literature, these models permit to characterise errors on any individual spectrum. The derived error models were validated in numerical simulations on a set of IIR filters approximating the input-output behaviour of a simply supported plate. Finally, they were shown to predict meaningful error bounds in a laboratory experiment where 2 forces acting on a suspended plate were to be identified. [References: 15]