Nature suggests that exploiting the elasticities and natural dynamics of robotic systems could increase their locomotion efficiency. Prior work on elastic snake robots supports this hypothesis, but has not fully exploited the nonlinear dynamic behavior of the systems. Recent advances in eigenmanifold theory enable a better characterization of the natural dynamics in complex nonlinear systems. This letter investigates if and how the nonlinear natural dynamics of a kinematic elastic snake robot can be used to design efficient gaits. Two types of gaits based on natural dynamics are presented and compared to a state-of-the-art approach using dynamics simulations. The results reveal that a gait generated by switching between two nonlinear normal modes does not improve the locomotion efficiency of the robot. In contrast, gaits based on non-brake periodic trajectories (non-brake orbits) are perfectly efficient in the energy-conservative case. Further simulations with friction reveal that, in a more realistic scenario, non-brake orbit gaits achieve higher efficiency compared to the baseline gait on the rigid system. Overall, the investigation offers promising insights into the design of gaits based on natural dynamics, fostering further research.

翻译：自然界启示我们，利用机器人系统的弹性和自然动力学特性可提高其运动效率。先前关于弹性蛇形机器人的研究支持这一假说，但未能充分利用系统的非线性动力学行为。本征流形理论的最新进展使复杂非线性系统中的自然动力学特性得到更精确的表征。本文探究运动学弹性蛇形机器人的非线性自然动力学能否以及如何用于设计高效步态。我们提出两种基于自然动力学的步态类型，并通过动力学仿真与现有先进方法进行对比。结果表明：通过在两种非线性模态之间切换产生的步态未能提升机器人运动效率；相反，基于无制动周期轨迹（无制动轨道）的步态在能量守恒条件下具有完美效率。进一步含摩擦仿真揭示，在更现实的场景中，基于无制动轨道的步态相比刚性系统的基准步态实现了更高效率。总体而言，本研究为基于自然动力学的步态设计提供了有前景的洞见，推动了相关领域研究的深入发展。