Experimental Results of a Fluid Actuated Morphing Winglet Trailing Edge

Kurzfassung

Designing active control surface technology into thin regions of aircraft wings is challenging due to small available volumes. To be able to do so is potentially beneficial to enable more efficient wing designs using morphing for e.g. load alleviation. This paper details a winglet trailing edge surface composed of fluid actuated morphing unit structures (FAMoUS) that enable control surface deflections under the corresponding aerodynamic hinge moments. These FAMoUS actuators are comprised of elastomer and metallic stiffeners, which under internal pressure from a fluid exert displacement and force and thus output work. Combining these unit structures in a bimorph setup a trailing edge control surface is build. This paper outlines the design, finite element analyses and manufacturing process of a demonstrator with 1 m span-width. These finite element analyses consist of detailed tuned material parameters obtained from testing on the individual unit structure tests as well as the inclusion of hydrostatic fluid elements to determine effective stiffnesses from the pressure-volume relationship between the housing structure and internal fluid. Manufacturing of the demonstrator is conducted using composite fabrication and machining techniques to ensure that the demanding tolerances and surface qualities are to be maintained. The structural part of the demonstrator is joint with an actuating system, where in combination wíth feedback sensors position control is achieved. The setup of the actuating system is introduced, elucidating the hydraulic system and the overall control design. Experimental results of tests are presented, starting with calibration of the feedback system with an external measurement, also clarifying deflection uniformity along the span of the demonstrator. Further results of deflection performance and deflection rate are presented and compared to the predictions derived from the finite element analyses. The findings are discussed and contextualized. A summary of the results is given and an outlook on the way forward is presented.