Bipedal animals have diverse morphologies and advanced locomotion abilities. Terrestrial birds, in particular, display agile, efficient, and robust running motion, in which they exploit the interplay between the body segment masses and moment of inertias. On the other hand, most legged robots are not able to generate such versatile and energy-efficient motion and often disregard trunk movements as a means to enhance their locomotion capabilities. Recent research investigated how trunk motions affect the gait characteristics of humans, but there is a lack of analysis across different bipedal morphologies. To address this issue, we analyze avian running based on a spring-loaded inverted pendulum model with a pronograde (horizontal) trunk. We use a virtual point based control scheme and modify the alignment of the ground reaction forces to assess how our control strategy influences the trunk pitch oscillations and energetics of the locomotion. We derive three potential key strategies to leverage trunk pitch motions that minimize either the energy fluctuations of the center of mass or the work performed by the hip and leg. We suggest how these strategies could be used in legged robotics.

中文翻译：

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躯干俯仰振动可在双足跑步鸟类和机器人中进行能量权衡。

双足动物具有多种形态和先进的运动能力。陆生鸟类尤其表现出敏捷，高效和强壮的奔跑运动，在这种运动中，它们利用了身体部位质量和惯性矩之间的相互作用。另一方面，大多数有腿的机器人不能产生这种通用且节能的运动，并且常常无视躯干运动来增强其运动能力。最近的研究调查了躯干运动如何影响人类的步态特征，但缺乏对不同双足动物形态的分析。为了解决此问题，我们基于具有原虫（水平）躯干的弹簧倒立摆模型分析了鸟类的奔跑。我们使用基于虚拟点的控制方案，并修改地面反作用力的排列，以评估我们的控制策略如何影响躯干俯仰振动和运动的能量。我们得出了三个潜在的关键策略，以利用躯干俯仰运动来最大程度地减少质心的能量波动或臀部和腿部所做的工作。我们建议如何在腿式机器人中使用这些策略。