Body-terrain interaction affects large bump traversal of insects and legged robots

Sm all animals and robots must often rapidly traverse large bump - like obstacles when moving through complex 3 - D terrains, during which, in addition to leg - ground contact, their body inevitably come s into physical contact with the obstacl es. However, we know little about the performance limits of large bump traversal and how body - terrain interaction affects traversal . To address these, we challenged the discoid cockroach and a n open - loop six - legged robot to dynamically run into a large bump of varying height t o discover the maximal traversal performance, and studied how locomotor modes and traversal performance are affected by body - terrain interaction . Remarkably, d uring rapid running, both t he animal and the robot were cap able of dynamically traversing a bump much higher than its hip height ( up to 4 times the hip height for the animal and 3 times for the robot, respectively) at traversal speeds typical of running, with decreasing traversal probability with increasing bump height. A stability analysis using a novel locomotion energy landscape model explained why traversal was more likely when the animal or robot approach ed the bump with a low initial body yaw and a high initial body pitch, and why deflection was more likely otherwise . Inspired by these principl es, we demonstrated a novel control strategy of active body pitch ing that increase d the robot's maximal traversable bump height by 75%. Our study is a major step in Bioinspiration & Biomimetics (2018), 13, 02600 5; htt ps://li.me.jhu.edu 2 establishing the framework of locomotion energy landscapes to understand locomotion in complex 3 - D terrains .