Identification of rigid body properties from vibration measurements

A knowledge of the rigid body properties of a structure can be important in vibration analysis, control, optimisation and structural dynamic problems in general. Whenever a system has a complicated shape and the location of its centre of mass and inertia tensor cannot be easily determined by purely theoretical tools, it may be convenient to use measured experimental dynamic data and to apply appropriate methods to evaluate those properties.In the present work a parametric modal identification method is investigated, for the simultaneous estimation of all the rigid body properties, using information from measured Frequency Response Functions encompassing the low-frequency modes. An important numerical tool has been developed to act as an indicator factor for mode shape selection, which can help to build the best available modal matrix. The accuracy of the estimated parameters is evaluated through the application of the method to a theoretical example, as well as to an actual structure specifically designed and built for this purpose.