Sensitivity of decoupling techniques to uncertainties in the properties

In this paper the decoupling problem, i.e. the identification of the dynamic behaviour of a structural subsystem, starting from information about the remaining part of the structural system (residual subsystem) and from the known dynamic behaviour of the complete system, is considered. In spite of promising applications, the decoupling problem presents some pitfalls that are difficult to avoid, such as lack of information on coupling DoFs (rotational DoFs) and ill-conditioning around particular frequencies. Two FRF based approaches are considered: an impedance based approach and a mobility based approach. In both approaches, the FRF matrix of the coupled system is assumed to be known at the coupling DoFs, and eventually at some internal DoFs of the residual subsystem. Information about the residual subsystem can consist either of measured FRFs or of a physical model. In the latter case, it is interesting to analyse how the predicted dynamic behaviour of the unknown subsystem is affected by uncertainties in the properties of the residual subsystem.