Department of Engineering, Stanford University, Stanford, CA 94305, USA.
Department of Engineering, Harvey Mudd College, Claremont, CA 91711, USA.
Integr Comp Biol. 2021 Sep 8;61(2):579-588. doi: 10.1093/icb/icab073.
The ability to glide through an arboreal habitat has been acquired by several mammals, amphibians, snakes, lizards, and even invertebrates. Lizards of the genus Draco possess specialized morphological structures for gliding, including a patagium, throat lappets, and modified hindlimbs. Despite being among the most specialized reptilian gliders, it is currently unknown how Draco is able to maneuver effectively during flight. Here, we present a new computational method for characterizing the role of tail control on Draco glide distance and stability. We first modeled Draco flight dynamics as a function of gravitational, lift, and drag forces. Lift and drag estimates were derived from wind tunnel experiments of 3D printed models based on photos of Draco during gliding. Initial modeling leveraged the known mass and planar surface area of the Draco to estimate lift and drag coefficients. We developed a simplified, 3D simulation for Draco gliding, calculating longitudinal and lateral position and a pitch angle of the lizard with respect to a cartesian coordinate frame. We used PID control to model the lizards' tail adjustment to maintain an angle of attack. Our model suggests an active tail improves both glide distance and stability in Draco. These results provide insight toward the biomechanics of Draco; however, future in vivo studies are needed to provide a complete picture for gliding mechanics of this genus. Our approach enables the replication and modification of existing gliders to better understand their performance and mechanics. This can be applied to extinct species, but also as a way of exploring the biomimetic potential of different morphological features.
几种哺乳动物、两栖动物、蛇、蜥蜴，甚至无脊椎动物都具有在树木栖息环境中滑翔的能力。飞龙科的蜥蜴拥有专门用于滑翔的形态结构，包括翼膜、喉垂和改良的后肢。尽管飞龙是最具特化的滑翔蜥蜴之一，但目前尚不清楚飞龙在飞行中如何有效地进行机动。在这里，我们提出了一种新的计算方法，用于描述尾巴控制对飞龙滑翔距离和稳定性的作用。我们首先将飞龙的飞行动力学建模为重力、升力和阻力的函数。升力和阻力的估计值是从基于飞龙滑翔时的照片的 3D 打印模型的风洞实验中得出的。初始建模利用飞龙已知的质量和平面表面积来估计升力和阻力系数。我们开发了一个简化的 3D 飞龙滑翔模拟，计算了蜥蜴相对于笛卡尔坐标系的纵向和横向位置以及俯仰角。我们使用 PID 控制来模拟蜥蜴的尾巴调整以保持迎角。我们的模型表明，尾巴的主动调整可以提高飞龙的滑翔距离和稳定性。这些结果为飞龙的生物力学提供了一些见解；然而，需要进一步的体内研究来提供这个属的滑翔力学的全貌。我们的方法可以复制和修改现有的滑翔器，以更好地了解它们的性能和力学特性。这不仅可以应用于已灭绝的物种，还可以探索不同形态特征的仿生潜力。
