Design exploration of a tensegrity twisting wing enabled by shape memory alloy wire actuation

Abstract

A modeling, experimental prototyping, and computational design exploration study of a morphing wing enabled by a tensegrity mechanism and actuated by shape memory alloy (SMA) wires is presented in this work. The studied wing design circumvents conventional control surfaces such as hinged flaps and ailerons through the implementation of a smooth wing shape that twists to modulate its flight characteristics. The continuous and smooth wing surface lessens aerodynamic drag to enhance aerodynamic efficiency. Computational fluid dynamic analyses confirmed superior lift-to-drag ratio of the twisting wing when compared to a conventional wing with a control surface. The morphing capability of the wing is enabled through an integrated lightweight tensegrity mechanism, which provides twisting motion through elongation/contraction of the SMA wires. Befitting for the actuation of the tensegrity mechanism due to their rod form, SMA wire actuators are incorporated to reconfigure the wing shape through thermally driven material actuation. The combination of a lightweight and compact tensegrity mechanism and SMA wire actuators eliminates the need for bulky components such as hydraulic and electric actuators to enhance the flight performance. A finite element model that integrates the wing, tensegrity mechanism, and SMA wire actuators is created to assess the stresses, maximum attainable twist angle, and structural mass of the wing. A design of experiment study is performed to evaluate the influence of the topological and geometrical design parameters on performance responses such as twist angle and mass. The most favorable design demonstrates a maximum twist angle of 15.85° and a mass of 2.02 kg without exceeding the material stress limits. The SMA-enabled torsional morphing capability is also demonstrated experimentally through a tensegrity twisting wing prototype equipped with commercially available SMA wire actuators.