Enhanced method for optimum driving point identification for modal testing

Abstract

Modal testing is used to experimentally determine the dynamic behavior of mechanical structures. The planning of the positions for exciting the structure, the so-called driving points, is essential for efficient experimental modal testing. Driving points are identified either by an initial assumption of possible excitation points and the experimental evaluation of their quality, or with the help of numerical models and indicators for optimal driving point selection. However, for practical applications, several driving points are usually required to excite all modes in the frequency range of interest, which is not covered in state-of-the-art indicators for driving point selection. This paper therefore presents a method for driving point identification with consideration of multiple driving points. Additionally, a criterion was developed that considers the excitability of modes, risks of double hits, and the excitation orientation simultaneously in order to increase the accuracy of the driving point identification. This criterion enables the evaluation of the excitation quality of each surface node and any mode combination using an automated selection method for determining the optimum set of driving points. The presented method assumes that natural frequencies and eigenvectors from preliminary numerical models are available for planning. By applying the method on application examples, the reduced effort required for a full modal analysis is demonstrated.