Design, Analysis And Development Of A Morphable Wing Structure For Unmanned Aerial Vehicle Performance Augmentation
Supekar, Abhijit Hiraman
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In this research, we propose mechanisms to continuously morph a wing from a lower aspect ratio to a higher and to further extremities of a gull and an inverted-gull configuration. The mechanism comprises of a linear actuator for the extension of the wing and the servo motors to obtain the gull and inverted gull configurations. The initial design and preliminary finite element representation using 3D-beams and plates in ANSYS Classic were the benchmarks to proceed for the detailed structural analysis of the complete wing in ANSYS Workbench. An elliptical pressure distribution at the quarter cord is assumed for the linear static structural analysis. From these results the modified 3D-CAD model developed in CATIA, is imported in ANSYS Workbench and used to compute the vibrational mode frequencies to avoid any resonance conditions due to the combined operation of the servo motors and the structure. The structure is also tested to ensure that the final model is light in weight and is stressed within the factor of safety. These results are useful for the next stage of the prototype development and its related instrumentation. A preliminary computational aerodynamic analysis conducted includes the use of the Athena Vortex Lattice (AVL) code to obtain basic aerodynamic parameters such as the drag polar and, lift curve slope and the pitching moment slope as functions of angle of attack. These results along with its comparison with the flight phases of the seagull provide an insight into the aerodynamic effects of morphing. Further, the wing is also tested numerically for static wing divergence speed at various stages of extension. A systematic method is developed to calculate the structural stiffness' of the wings non-uniform geometry which changes over the span. Thus, the torsional deformation and influence function is calculated and the static wing divergence speed is determined. An observation of the change of divergence speed with the changes in the aspect ratio is made. Finally, the wing prototype is tested in low-speed wind tunnel, and thus used to validate the aerodynamic benefits of morphing. It is not the goal of this research to mimic bird kinematics. Rather, the objective is to select a biologically-inspired system to improve the range of achievable flying conditions for an Unmanned Aerial Vehicle (UAV).