In the present work are presented both experimental and numerical simulation results obtained with an open-loop control law applied to an individual blade control system that incorporates a mechanism for blade active impedance adaptation at the root, the active pitch link or "smart spring". It is demonstrated that the active pitch link provides parametric excitation of the blade in the rotating frame and, with it, alters the vibration spectra of the vibration loads both in the blade structure and transmitted to the nonrotating frame by the hub. The experimental results were obtained in whirl tower tests where blade periodic excitation was provided by a fan located at the base of the rotor and generated a transversal flow at a range of blade azimuth angles.

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Conference 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
Nitzsche, F, Feszty, D, Grappasonni, C. (Chiara), & Coppotelli, G. (Giuliano). (2013). Whirl-tower open-loop experiments and simulations with an adaptive pitch link device for helicopter rotor vibration. In Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference.