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 (those involving "mechanical intelligence"), they fail to reproduce the performance of even the simplest organisms. To uncover 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 used a model biological system, the highly studied nematode worm Caenorhabditis elegans, and a robophysical device whose bilateral actuator morphology models that of limbless organisms across scales. The robot's kinematics quantitatively reproduced the performance of the nematodes with purely open-loop control; mechanical intelligence simplified 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, robustified 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 design and control paradigm for limbless robots for applications like search and rescue and planetary exploration.
The Conversation: We designed wormlike, limbless robots that navigate obstacle courses − they could be used for search and rescue one day Nature Reviews Electrical Engineering: Controlling limbless locomotors with mechanical intelligence DeepTech and MIT Technology Review (Chinese): 佐治亚理工中国博士开发最新无肢机器人,揭示机械智能原理,有望用于极端环境探索 American Scientist: Slithering Robots to the Rescue Georgia Tech Research News: Worms Inspire Wiggly Robots That Navigate All Landscapes
@article{wang2023mechanical, author = {Tianyu Wang and Christopher Pierce and Velin Kojouharov and Baxi Chong and Kelimar Diaz and Hang Lu and Daniel I. Goldman}, title = {Mechanical intelligence simplifies control in terrestrial limbless locomotion}, journal = {Science Robotics}, volume = {8}, number = {85}, pages = {eadi2243}, year = {2023}, doi = {10.1126/scirobotics.adi2243}, URL = {https://www.science.org/doi/abs/10.1126/scirobotics.adi2243}, eprint = {https://www.science.org/doi/pdf/10.1126/scirobotics.adi2243} }