Evolutionary Flight and Enabling Smart Actuator Devices

摘要

Recent interest in morphing vehicles with multiple, optimized configurations has led to renewed research on biological flight. The flying vertebrates - birds, bats, and pterosaurs - all made or make use of various morphing devices to achieve lift to suit rapidly changing flight demands, including maneuvers as complex as perching and hovering. The first part of this paper will discuss these devices, with a focus on the morphing elements and structural strong suits of each creature. Modern flight correlations to these devices will be discussed and analyzed as valid adaptations of these evolutionary traits. The second part of the paper will focus on the use of active joint structures for use in morphing aircraft devices. Initial work on smart actuator devices focused on NASA Langley's Hyper-Elliptical Cambered Span (HECS) wing platform, which led to development of a discretized spanwise curvature effector. This mechanism uses shape memory alloy (SMA) as the sole morphing actuator, allowing fast rotation with lightweight components at the expense of energy inefficiency. Phase two of morphing actuator development will add an element of active rigidity to the morphing structure, in the form of shape memory polymer (SMP). Employing a composite structure of polymer and alloy, this joint will function as part of a biomimetic morphing actuator system in a more energetically efficient manner. The joint is thermally actuated to allow compliance on demand and rigidity in the nominal configuration. Analytical and experimental joint models are presented, and potential applications on a bat-wing aircraft structure are outlined.