System identification of a reduced scale model blade with an adaptive pitch link using whirl tower test data

In this paper the identification of the dynamic properties of a rotating helicopter blade has been performed using data recorded during whirl tower tests. A new methodology has been developed in order to extend the applicability of the operational modal analysis to systems characterized by harmonic component excitations blended with white noise spectra loading. The proposed approach is able to identify the harmonic components and then to remove their effects on the time responses of the system. The capabilities of the such method to track the changes in the natural frequencies, damping ratios and mode shapes of the rotating helicopter blade will be investigated in order to asses the overall efficiency. Furthermore, the experimental findings will be compared to those numerically achieved using an aeroelastic numerical procedure developed to deal with the dynamics of rotating blades. Finally, the effects of changes of the stiffness of the pitch link, located at the root of the rotating blade, on the modal parameters will be investigated. © 2012 AIAA.