Therefore, in this work the elbow and the wrist represent an approximated minimum set of coordinates that is required to define the overall wing shape. However, within gliding flight extension/flexion dominates the range of motion and thus we have limited our study to focus only on the range of motion of extension and flexion for the elbow and the wrist (hereafter referred to as ‘joint-driven wing morphing’). the ability to extend/flex, pronate/supinate and elevate/depress. These joints have three degrees of freedom, i.e. Active manipulation of only two skeletal joints, the elbow and wrist is responsible for the majority of this wing shape change ( figure 1). When the applicable muscles are activated, the non-planar musculoskeletal linkage causes three-dimensional (3D) changes to the overall wing geometry. By contrast, bird wings are composed of an underlying musculoskeletal system that can be approximated as a non-planar six-bar linkage system. The majority of current engineered morphing wings adjust their wing geometry discretely within one or two planes, such as span, sweep, dihedral, etc. Therefore, it is of no surprise that as engineers strive towards the objective of an adaptive, multifunctional UAV, bird wings have directly and indirectly inspired many morphing wing designs. In addition, UAVs often face aerodynamic control challenges including the need to adapt to variable environmental conditions or manoeuvre through complex territories, while birds complete similar tasks with apparent ease. The adaptability offered by avian wing morphing is highly desirable for UAVs as it may broaden the efficient operational range, reduce operating costs as well as offer enhanced or novel capabilities.
In comparison, fixed-wing unmanned aerial vehicles (UAVs) are often designed to satisfy specific functions, such as high-altitude surveillance or long endurance flights, and efficient operation is limited to their intended mission parameters. Previous research has shown that active wing morphing allows birds to dynamically adapt their aerodynamic performance and stability characteristics in response to changing flight conditions or requirements. The adaptability demonstrated by birds is in part due to their ability to morph the shape of their wings, both actively and passively. Collectively, our results show that gull-inspired joint-driven wing morphing allows adaptive longitudinal flight control and could promote multifunctional UAV designs.Ī bird can begin its day foraging in a slow glide, suddenly needing to evade a predator, only to later fly home battling an incoming storm. Further, extension along the trajectory inherent to the musculoskeletal linkage system produced the largest changes to the investigated aerodynamic properties. We identified two unique trajectories that decoupled stability from lift and pitching moment generation. Within the range of wing extension capability, specific paths of joint motion (trajectories) permit distinct longitudinal flight control strategies. We found that joint-driven wing morphing effectively controls lift, pitching moment and static margin, but other mechanisms are required to trim. We used a numerical lifting-line algorithm (MachUpX) to determine the aerodynamic loads across the range of motion of the elbow and wrist, which was validated with wind tunnel tests using three-dimensional printed wing-body models. Here, we investigated if joint-driven wing morphing is desirable for UAVs by quantifying the longitudinal aerodynamic characteristics of gull-inspired wing-body configurations. By contrast, avian joint-driven wing morphing produces a diverse set of non-planar wing shapes. This in-flight adaptability has inspired many unmanned aerial vehicle (UAV) wings, which predominately morph within a single geometric plane.
Birds dynamically adapt to disparate flight behaviours and unpredictable environments by actively manipulating their skeletal joints to change their wing shape.
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