Limbless locomotors, from microscopic worms to macroscopic snakes, traverse complex, heterogeneous natural environments typically using undulatory body wave propagation. Theoretical and robophysical models typically emphasize body kinematics and active neural/electronic control. However, we contend that because such approaches often neglect the role of passive, mechanically controlled processes (i.e., those involving mechanical intelligence), they fail to reproduce the performance of even the simplest organisms. To discover principles of how mechanical intelligence aids limbless locomotion in heterogeneous terradynamic regimes, here we conduct a comparative study of locomotion in a model of heterogeneous terrain (lattices of rigid posts). We use a model biological system, the highly studied nematode worm C. elegans, and a novel robophysical device whose bilateral actuator morphology models that of limbless organisms across scales. The robot's kinematics quantitatively reproduce the performance of the nematodes with purely open-loop control; mechanical intelligence simplifies control of obstacle navigation and exploitation by reducing the need for active sensing and feedback. An active behavior observed in C. elegans, undulatory wave reversal upon head collisions, robustifies locomotion via exploitation of the systems' mechanical intelligence. Our study provides insights into how neurally simple limbless organisms like nematodes can leverage mechanical intelligence via appropriately tuned bilateral actuation to locomote in complex environments. These principles likely apply to neurally more sophisticated organisms and also provide a new design and control paradigm for limbless robots for applications like search and rescue and planetary exploration.

翻译：从微观蠕虫到宏观蛇类，无肢运动生物通常通过波状身体传播来穿越复杂异质自然环境。理论和机器人物理模型通常强调身体运动学与主动神经/电子控制。然而我们认为，由于此类方法常忽视被动机械控制过程（即涉及机械智能的过程），因此无法复现甚至最原始生物的运动表现。为揭示机械智能如何辅助异质地貌环境下无肢运动的原理，我们以刚性柱体阵列构成的异质地形模型开展比较研究。采用模式生物系统——被广泛研究的秀丽隐杆线虫，以及新型机器人物理装置（其双侧致动器形态可跨尺度模拟无肢生物）。该机器人在纯开环控制下定量复现了线虫的运动表现；机械智能通过减少主动传感与反馈需求，简化了障碍导航与利用的控制。在线虫中观察到的主动行为——头部碰撞时的波状前进逆转，通过利用系统机械智能增强了运动鲁棒性。本研究揭示了神经简单的无肢生物（如线虫）如何通过适当调谐的双侧致动器利用机械智能在复杂环境中运动。这些原理可能适用于神经更复杂的生物，并为搜救、行星探测等领域的无肢机器人提供新型设计与控制范式。