Near-to-node modal identification using multiple related response models

Abstract

Abstract Experimental modal analysis (EMA) is a well-established procedure for determining the modal parameters of a structure. Typically, a point-force is used to excite the structure and the translational response is measured. When performing an EMA, problems with a reliable modal-parameter estimation can arise whenever a selected reference point is located in the proximity of a node for any mode shape in interest. This problem can be addressed by performing multi-reference measurements; however, a non-coincidental position with respect to the remaining nodes cannot be guaranteed. In this research a novel modal-identification method, based on multiple related experimental response models at a single reference point, is proposed as an alternative to the established multi-reference measurement. The idea is to combine multiple response models of the same structure, acquired by different types of sensors (e.g., translational and rotational) for which the nodes of the response-related modal shapes do not coincide. The Least-Squares Frequency-Domain (LSFD) method is modified by considering the mutual relations of the acquired response models. The proposed methodology is experimentally validated on a homogeneous aluminium beam. The proposed method shows both a successful modal identification and an increased consistency of the identified modal constants, despite the proximity of the nodes to the selected reference point.