Abstract
In this paper, a subspace fitting method is proposed to update, in the time domain, the finite element model of a rotating machine. The procedure is achieved by minimizing an error norm, leading to the comparison between experimental and theoretical observability matrices. Experimental observability matrix is obtained through a MOESP subspace identification algorithm, by projecting the output signal onto some appropriate subspaces, resulting in a cancellation of input excitations and noises. The theoretical observability matrix is obtained from modal parameters of a finite element model of the structure. The minimization procedure is carried out through a Gauss-Newton algorithm. The method is applied to determine the foundation stiffness of an experimental rotating machine subject to a random noise.
Highlights
Evaluating damages occurring in mechanical systems constitutes a tough task
The methods based on Finite Element (FE)
The purpose of SI techniques [5] is to consider a discrete modal state-space representation of the form qk+1 = Λqk + Bmoduk + wk yk = Φobsqk + vk where uk and yk are the vectors of input and output data, respectively; Λ is a diagonal matrix of eigenvalues; Bmod and Φobs are matrices expressed in terms of the mode shapes of the structure; wk and vk are vectors of noises while qk is a vector of generalized coordinates
Summary
Evaluating damages occurring in mechanical systems constitutes a tough task. Their emergence and evolution are characterized by variations (those can be small) of the dynamic properties of structures [1]. Many damage diagnosis methods have been proposed to carry out this issue. The methods based on Finite Element (FE)
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