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Degree of deformation and power consumption of compliant and rigid-linked mechanisms for variable-camber morphing wing uavs

Abstract:

Compliant and rigid linked mechanisms —actuated by servomotors— are workable approaches to modify the airfoil camber by means of the deformation of the leading and/or trailing edge. The aerodynamic benefits of the aforesaid approaches are well documented; nevertheless, there is little data about their geometric deformability and the power/energy required to attain this. In this context, this work presents the numerical and experimental investigation of the deformation capabilities and the power/energy requirements of compliant and rigid-linked mechanisms for variable-camber morphing wings implemented in UAVs. Specifically, this paper determines for both mechanisms the fitting error and the power consumption when a baseline airfoil (NACA-0012) morphs into a series of low-Reynolds target airfoils, widely used in small and medium fixed-wing UAVs. In the case of the compliant morphing wing, the numerical approach consists on the parametric sizing of the compliant airfoil using a pseudo-rigid parametric model and numerical simulations using FEM. In what respect to the rigid-linked mechanism, the numerical investigation comprises the kinematics assessment using a graphical method and the Newton-Euler equations. A 3D CAD model and a prototype have been developed for each variable-camber morphing wing approach, which have been tested experimentally in a subsonic wind tunnel. The experiments consisted on measuring the energy required to morph into a target airfoil and the power per unit of time to retain the morphed configuration under the effect of the aerodynamic loads. Simultaneously, the fitting of the morphed airfoil respect to the target airfoil was evaluated graphically. Results indicate that both, the compliant and the rigid-linked mechanisms, permit to produce large camber deformations. Nevertheless, the compliant wing deforms more smoothly and fits better to the target airfoil in contrast with the rigid-linked wing, which produces non-continuous deformations. On the other hand, the compliant wing consumes about twice as much power to morph into the target airfoil and keep up the deformed geometry, compared to the rigid-linked wing.