S8-4 Monday, Jan. 6 09:00 - 09:30 Body lateral deformation and compliance help snakes and snake robots stably traverse large steps FU, Q; GART, SW; MITCHEL, TW; KIM, JS; CHIRIKJIAN, GS; LI, C*; Johns Hopkins University email@example.com https://li.me.jhu.edu/
Many snakes live in mountains and forests and traverse large obstacles comparable to their body size. Similarly, snake robots have the potential to traverse terrain with large obstacles like earthquake rubble and construction sites for search and rescue and structural examination. Although snake locomotion on flat surfaces is inherently stable, in such complex terrain, snakes must deform their body in three dimensions, during which maintaining stability becomes a challenge. Here, we review recent progress in our group in this problem. We studied how the generalist variable kingsnake traversed a large step as high as 40% body length. We developed a method to reconstruct continuous body 3-D motion (both position and orientation) from marker tracking. We discovered that the snake combined lateral body oscillation and cantilevering to traverse stably. The body sections below and above the step oscillated laterally on the surface, which provided not only propulsion but also roll stability as the body section in between cantilevered in the air to bridge the large height increase. To further understand stability principles, we developed a robotic snake with a similar gait as a physical model to study how traversal depended on step height and body compliance. As step height increased, the robot with a rigid body rolled and flipped over more often, leading to frequent failure. By contrast, the snake that had a compliant body rarely suffered this problem. Adding body compliance to the robot reduced its roll instability during traversal by improving body contact with the terrain. Besides advancing understanding of snake locomotion, our robot achieved traversal speeds surpassing most previous snake robots and approaching that of snakes, while maintaining high traversal probability on steps as large as 40% body length.