Output-only modal parameter estimation for time-varying structures using a time-frequency-domain least square approach

When time-varying structures are in operational conditions and under natural stochastic excitations, the responses are always nonstationary stochastic signals, of which the spectra change with time. This paper studies the time-dependent power spectrum density based on time-frequency analysis. A mathematical model of the time-frequency-domain least square modal parameter estimator for time-varying structures based on the time-dependent power spectrum density is presented. The parametric structural dynamic model for modal parameter estimation is the common-denominator model and the leading coefficients of the denominator and numerator polynomials are the estimated parameters. In addition, the transformations from the leading coefficients of the denominator and numerator polynomials to the modal parameters are proposed. A numerical simulation example validates this modal parameter estimator for timevarying structures.