Method for determining modal parameters

The present invention relates to a method for determining modal parameters of a system under test. The method comprises the steps of - taking a first set of values of output signals obtained under a first loading condition of the system, - determining for said first loading condition a parametric matrix model for the system, said parametric matrix model representing a space orthogonal to the space spanned by the output signals, said space being at least two dimensions smaller than the number of output signals, so that the influence of input spectra is reduced, - determining for the first loading condition parameters of the parametric matrix model, - expressing a polynomial eigenvalue problem based on the parametric matrix model and the corresponding parameters for that first loading condition, - deriving additional information about the system under test by considering a second set of values of the output signals obtained under a second loading condition of the system and determining for the second loading condition a parametric matrix model and its parameters, or by considering prior knowledge about the system under test, - adapting the polynomial eigenvalue problem using said additional information, so that a complete set of equations is obtained, - obtaining the modal parameters by solving the adapted polynomial eigenvalue problem.