Sensors location for updating problems

In this paper two methods are proposed in order to determine the optimal or near-optimal positioning of sensors which has to be carried out when vibra tion tests are being prepared. The optimal sensors location is proposed on the finite element model associated to the structure to be tested. The gene ral context concerns the parametric identification of mechanical structures models using test results. The purpose of model updating is to converge th e mathematical model, generally obtained by a finite element method, by adj usting the model parameters in agreement with test measurements. Missing di splacement measurements increase the ill-posedness of this problem. The dyn amic response of the structure is here described on a truncated modal basis . The first method of location of sensors emphasises the minimisation of th e noise effect, the estimate of the modal coordinates is found in a least-s quares sense. The second method is based on the observability gramian and t he optimal sensors location has to ensure observability requirements. The s mallest eigenvalue of the observability gramian represents the poorest case of information. The two methods are illustrated for a supported beam for a benchmark truss structure. (C) 1999 Academic Press.