Design Of A Morphing Winglet Trailing Edge With Fluid Actuation : Design Process And Experimental Results

Abstract

Integrating active control surface technology into aircraft wings with confined spaces is challenging. It would be beneficially to do so to enable more efficient wing designs fore.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. The design of the FAMoUS actuators is 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, which is structural and actuating part at the same time. The structural dimensioning of a demonstrator with 1 m span-width is shown, based on a finite element analyses consisting 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. The process of choosing a suitable actuating system including the feedback control and hydraulic systems is presented. Finally 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. Deflection performance and deflection rate are discussed and compared with the predictions 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.