ABSTRACT Autonomous modal parameter estimation is an attractive approach when estimating modal parameters (frequency, damping, mode shape, and modal scaling) as long as the results are physically reasonable. Frequently, significant post processing is required to tune the autonomous estimates. A general autonomous method is demonstrated with no post processing of the modal parameters. Example case histories are given for simple measurement cases taken from the laboratory (circular plate) as well as realistic field measurement cases involving significant noise and difficulty (bridge). These application case histories explore the successes and failures of the autonomous modal parameter estimation method and demonstrate the limitations of practical application of automated methods.

Recent work with autonomous modal parameter estimation has shown great promise in the quality of the modal parameter estimation results when compared to results from traditional methods by experienced users. While autonomous modal parameter estimation means slightly different things to different researchers and practitioners, for the purpose of this discussion, autonomous will require an automated procedure which sorts and processes a large number of possible modal parameter solutions to yield one consistent estimate with no user interaction after initial thresholds are chosen. In the work discussed, this final, consistent set of modal parameters is identifiable due to the combination of temporal and spatial information in a domain state vector of relatively high order (5-10). Since this domain state vector has both complex modal frequency and modal vector information as embedded content, sorting consistent estimates from the multitude of possible solutions is relatively trivial. Because this domain state vector can be developed from the results of any modal parameter estimation method, possible solutions from different traditional methods can be utilized in the autonomous procedure to yield one consistent set of modal parameters.