Further developments on the estimation of rigid body properties from experimental data

The evaluation of the rigid body properties of a structure is a very important issue for the study of its dynamic behaviour when the influence of the rigid body modes is considerably significant.Various approaches exist for this purpose. In the present work the authors explore a particular group of methods where ten rigid body properties are estimated from modal information extracted from Frequency Response Data (FRF) measured on structures. This kind of methods, usually known as modal methods, use the identified modal properties associated to the rigid body modes and their orthogonality properties. However, some difficulties have been reported in cases when a high degree of symmetry exists in the structure, when double modes appear or when it is not possible to excite all the six rigid body modes. New improvements and methodologies are proposed to help solving such situations.