Meeting Abstract
Snakes move well in complex 3-D terrain such as mountains and deserts with large step-like obstacles. Our recent study discovered that a generalist kingsnake (Lampropeltis mexicana) uses a partitioned gait to traverse large steps [1]. The snake’s body sections towards the head and tail undulate on the horizontal surface to propel and stabilize the animal, while the middle body section cantilevers in the sagittal plane to bridge across the large step. Despite such high degree-of-freedom body deformation, the animal always maintains good contact with the ground. Here, we use robophysical experiments to test the hypothesis that body compliance is critical to maintaining contact with the terrain to maintain traction and stability. We developed a snake robot that can deform its body in both horizontal and sagittal planes, with one-way wheels to mimic anisotropic friction of snake scales, and used an adjustable suspension system to vary body compliance. Using a snake-inspired partitioned gait, the robot traversed a large step as high as 40% its body length. As compared to using a more rigid suspension, when the suspension was more compliant, the robot maintained better contact with the ground (from 81 ± 8 % of the time to 87 ± 5 % of the time) thanks to larger suspension compression (from 1.0 ± 0.3 mm to 2.1 ± 0.6 mm). This increased traversal probability (from 50% to 90%) for high steps (36% and 38% of body length), but with a sacrifice of higher power consumption (from 24.9 ± 1.4 W to 26.4 ± 1.4 W) and more undulation cycles needed to traverse (from 6.02 ± 2.32 to 8.89 ± 5.17) (P < 0.05 for all tests, ANCOVA). Our study demonstrated the importance of body compliance for snakes and snake robots to engage and traverse complex 3-D terrain. ([1] See another talk: Gart SW et al., Snakes partition their body to traverse large steps and inspire a snake robot.)
