<p dir="ltr">Birds are capable of landing at high angles of attack, reducing the time and space required&nbsp; to land, while maintaining control over their descent rate and location. In contrast, many bird-scale, unmanned aerial vehicles (UAVs) must land in a net, be caught by hand, or require a long runway for roll-out.&nbsp;In this study, a bio-inspired wing folding system was designed to create a destabilizing pitching moment that allows a small scale UAV to land quickly by controlling its stall behavior. Birds accomplish this by sweeping their wrist and elbow inwards, forming an M-shaped wing. The M-shaped wing shifts the center of pressure forward of the center of gravity. In this paper, we develop an analytical model and gradient-based optimization to determine the M-shaped wing angles required to shift the center of pressure. The wing span and aspect ratio are inspired by the Harris Hawk wing geometry. A four bar linkage is designed to couple the wrist and shoulder motions and reduce the number of actuators required to morph the wing from the fully extended stable state to the M-shaped agile state. The morphing wing was actuated under aerodynamic loads through wind tunnel experiments at angles of attack and M-sweep angles. Results show the effect of the M-shape geometry on pitching and roll moments, lift, and drag.</p>

Bird-Inspired Morphing Wings: Design and Experimental Evaluation of a Wing Folding Mechanism for Pitch Stability Control

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2021/volume/85499

ASME 2021 Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS2021)

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