Improvement of Artificial Foldable Wing Models by Mimicking the Unfolding/Folding Mechanism of a Beetle Hind Wing

In an attempt to realize a flapping wing micro-air vehicle with morphing wings,we report on improvements to our previous foldable artificial hind wing.Multiple hinges,which were implemented to mimic the bending zone of a beetle hind wing,were made of small composite hinge plates and tiny aluminum rivets.The buck-tails of rivets were flared after the hinge plates were assembled with the rivets so that the folding/unfolding motions could be completed in less time,and the straight shape of the artificial hind wing could be maintained after fabrication.Folding and unfolding actions were triggered by electrically-activated Shape Memory Alloy (SMA) wires.For wing folding,the actuation characteristics of the SMA wire actuator were modified through heat treatment.Through a series of flapping tests,we confirmed that the artificial wings did not fold back and arbitrarily fluctuate during the flapping motion.