Development of the Mode Isolation Algorithm for Experimental Modal Analysis

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

Principal Investigator: Jerry H. Ginsberg The G. W. Woodruff School of Mechanical Engineering Georgia Institute of Technology NSF Proposal number 0098539 Development of the Mode Isolation Algorithm for Experimental Modal Analysis Abstract Experimental modal analysis fits measurements of response data to canonical equations representing the analytical response of dynamical systems. The objective is to identify the natural frequencies, damping characteristics, and modal vibration patterns. Such knowledge can be used as a diagnostic tool for existing systems, as well as to identify and correct analytical model shortcomings. The project will develop a new algorithm for performing such tasks. The algorithm iteratively identifies modes, then subtracts them from the data, in order reveal modes that are less evident. A specific objective of the project is to provide a robust method for systems that exhibit strong modal coupling, in which individual modes lose their distinctiveness. Hence, the algorithm will be more widely applicable than the most sophisticated of the current approaches, yet it will retain the simplicity of implementation offered by elementary methods. The primary tasks for the proposed work are to implement and validate the algorithm when it is used to fit measured data to a state-space modal analysis formulation that accounts for arbitrary damping, gyroscopic, feedback, and circulatory forces. These developments will significantly improve the ability to perform experimental modal analysis of complex structures composed of advanced composite materials. Furthermore, enhancing the ability to correctly identify modal properties will lead to designs that use materials more economically. Also, by raising the level of experimental error that is acceptable, the algorithm will lead to cost reductions in experiments. Success in attaining the project objectives will have a major impact wherever vibration control is an issue.