3D Avian bipedal locomotion in even and unpredictable environments: an integrative study of locomotion control, body and leg proportions

两足动物大约在2.3亿年前在始祖龙身上进化出来，始祖龙包括鳄鱼和恐龙，它们是现代鸟类的最新祖先。今天有将近10,000种鸟类。他们中的许多人可能很好地适应了地面运动，使用步行和跑步的步态，但也使用其他步态，如接地跑(没有空中阶段的跑步)或混合步态(步行和跑步的组合)。此外，在鸟类内如此多的物种中，由于生态和生物力学要求的差异，后肢形态也有相当大的差异。在陆地运动中，肢体节段的形态适应既影响整个肢体的运动，也影响肢体节段之间的相对运动。鸟类提供了一个自然的动物模型，用于理解跨步两足动物的功能需求，以及这些需求如何随着身体大小或腿部分段比例的变化而变化。本科学提案的目标是阐明以下问题：i)什么是仍能保证稳定运动的建设性(形态)比例？Ii)生态和生物力学因素如何影响鸟类后肢的设计，以及这种设计如何限制均匀和扰动运动中的前馈和反馈控制？Iii)鸟类如何在受干扰的运动中控制它们的前额躯干？Iiii)腿段长度和运动学可以预测吗？为了探讨这些问题，我的目标是将完整的3D实验(包括同步测量X射线透视、地面反作用力和肌肉激活)与数值模拟相结合。实验将使我能够在均匀、粗糙和不可预测的地形上计算非常精确的3D逆动力学。通过使用肌电图仪，我将研究肌肉准备和激活策略，在触地之前和接触过程中，通过跨栏或洞，以及它们与腿部几何形状的关系。实验还将提供与模板(模型)相关的躯干和腿策略，以应对崎岖的地形，这将在数值模拟中进行测试。数值模拟还将帮助我调查哪些是确保鸟类和恐龙自我稳定运动的建设性(形态)特征。我的目的是解释基于稳定性和能量最小化的禽类身体比例和腿部比例。此外，我还希望揭示躯干平衡和腿部比例如何影响在地形不平坦和不规则的陆地环境中导航的能力。所开发的实验和仿真方法可能有助于预测现存和灭绝的两足动物的步态、运动速度和节段运动学，也可能推动仿生机器人的新设计路线。

Bipedalism evolved about 230 million years ago in archosaurs, a group that includes crocodilians and dinosaurs, being the most recent ancestors of modern birds. Today there exist nearly 10,000 bird species. Many of them are likely well adapted for terrestrial locomotion, use walking and running gaits, but also other gaits such as grounded running (running without aerial phases) or mixed gaits (a combination of walk and run). Across such a great number of species within birds, there is, in addition, considerable variation in hindlimb morphology relating to differences in ecology and biomechanical demands. Morphological adaptations of limb segments influence both the motions of whole limb and the relative motion of the limb segments to one another during terrestrial locomotion. Birds provide a natural animal model for understanding the functional demands of striding bipedalism and how these demands change with body size or leg segment proportions. The goals of the present scientific proposal is to bring light about the following questions: i) What are the constructive (morphological) proportions which still assure stable locomotion? ii) How do ecological and biomechanical factors influence avian hindlimb design and how this design constrains feedforward and feedback control during even and perturbed locomotion? iii) How do birds control their pronograde trunk during perturbed locomotion? iiii) Can leg segment length and kinematics be predicted? To approach these questions, I aim to combine full 3D-experiments (involving synchronously measurement of X-ray fluoroscopy, ground reaction forces and muscle activation) with numerical simulations. Experiments will allow me to compute a very precise 3D inverse dynamics on even, rough and unpredictable terrains. By using electromyography, I will investigate muscular preparation and activation strategies prior to touch down and during contact when negotiating a hurdle or a hole and their relation to leg geometry. Experiments will also deliver template (model) related trunk and leg strategies to negotiate with rough terrain, which will be tested in numerical simulations. Numerical simulations will also help me to investigate which are the constructive (morphological) features that assure self-stable locomotion in birds and dinosaurs. I aim to explain avian body proportions and leg segment proportions based on stability and energy minimization. Also I expect to uncover how trunk balance and leg proportions influence the ability to navigate on terrestrial environments with uneven and irregular terrain. The developed experimental and simulation methods may help to predict gaits, locomotion speeds and segment kinematics of extant and extinct bipeds and may also impulse new design paths in bio-inspired robots.