Time-Frequency Analysis for Transfer Function Estimation and Application to Flutter Clearance

Atransferfunction estimationprocedurethatrelies on thetime-frequency analysis of input and output signalsis described. This method was developed in an attempt to better identify the aeroelastic behavior of NASA Dryden’ s F-18 systems research aircraft and to predict its e utter boundaries using in-e ight experimental data. Numerical experimentson e eld data show thatexploiting thetime-frequency characteristics of the excitation inputscan bring enhanced accuracy and cone dence when identifying multi-input/multi-output transfer functions. In particular, the proposed approach complements many well-established black-box identie cation procedures by providing an independent way to obtain transfer function estimates. A computational tool implementing this approach is now being evaluated for practical use at NASA Dryden Flight Research Center.