Stability in Modal Identification: Numerical Analysis of a Subspace Method

M. Goursat (France)


Identification, Modal Analysis, Numerical Stability, Mod elling


Different classical methods (in frequency or time domain) for modal identification have a common tool: the stabiliza tion diagram. In this paper we use the covariance driven subspace method used in a blind situation (input unknown). One of the well-known problems in most of identification methods is that we get spurious (computational) modes to gether with the true ones and we do not know the true order of the system. We give the different choices for the main algorithm with illustrative results for practical examples. We compare the stability of two modes and show a possible procedure to avoid the choice of a spurious mode in the modal signature of the structure. Then we show the results of computations for different implementations of the algorithm and try to define a procedure in order to improve the quality and the reliability of the estimations of the damping parameters.

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