## 4 Multidisciplinary Design, Analysis, and Optimization of an Adaptive Wing
### Adaptive Wing Actuation Design  
The key aspect of the proposed method is that it takes advantage of the interaction between the aerodynamic loads and the structural design of the internal actuators to improve the airfoil's performance. This section describes the wing structure, the actuators, and the finite element modeling.  
An adaptive wing was designed to be small and compact so that it could be installed inside the UAV S45 wing; it achieves the required deformations via its distributed hinge-less structure. The compression forces and twisting motions are supported by a redesigned wing box, which allows the decoupling of aerodynamic loads in the spanwise and chordwise directions. This adaptive wing model is designed using a structure composed of segments of different thicknesses connected to its rear spar. When bent under the actuators' force, the space between the plate in the middle and the actuators on the upper surface is filled with polymer foam and honeycomb structures with a high stiffness-to-weight ratio. The compression modulus and dynamic fatigue are properties that assess the foam's ability to support external weight and to retain its reference shape. For instance, when the leading and trailing edge are moving in the downwards direction the bottom half of the material covering the plates will be compressed, while the upper half will be elongated. These two actions lead to an increase in concavity for the inner part and an increase in convexity for the upper part, and thus to an equivalent increase in camber.  
Figure 8 shows the FEA of the angular position variation on the leading edge and trailing edge produced by the actuation system. Both the leading and the trailing edge surfaces must be able to move up to 30\({}^{\circ}\) in the upward and downward positions.  
Figure 9 shows the FEA results measured in terms of stress (in MPa) on the actuation system \"arm\" and \"fixation\" at different angular positions of the airfoil leading edge and trailing edge. This evaluation was necessary to validate that the actuation system can displace/move the leading edge and the trailing edge when the airflow is moving at a speed of 30.1 m/s on the prototype surface.  
Figure 7: The adaptive wing multidisciplinary optimization methodology.  
Figure 10 shows the bench test validation of the FEA results for the angular position displacements of the leading edge and trailing edge. This bench test also allowed the validation of the script code written by the main author, and it was used to control the leading edge and trailing edge positions with a feedback signal from the accelerometer inside the wing prototype.  
Figure 8: Leading edge and trailing edge angular position variation produced by the actuation system.  
Figure 10: Bench tests of the wing prototype for the FEA results validation.  
Figure 9: FEA results on the actuation system.  
The UAV wing prototype's actuation is achieved by four servo motor drives that change the wing shape with the structural stresses applied to its polymer skin. The advantages of this skin are the stiffness and the nonlinearity of the material behavior with respect to the stress-strain and to the actuation level-produced force relationships. These actuator motions were modeled in a 3D CAD that considers the results of the structural finite element analyses found with ANSYS FEA software. The following section describes the definition of the goals of the optimizer and the results of the optimization.