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

TL;DR

This study investigates how body-terrain interactions influence the ability of insects and robots to traverse large bumps, revealing key factors and control strategies that enhance traversal performance in complex terrains.

Contribution

It introduces a locomotion energy landscape framework and demonstrates a novel active body pitching control to significantly improve bump traversal in robots.

Findings

Both animals and robots can traverse bumps up to 4 times their hip height at typical running speeds.

Low initial body yaw and high initial body pitch increase traversal likelihood.

Active body pitching control increases maximum bump traversal height by 75%.

Abstract

Small 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 comes into physical contact with the obstacles. 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 an open-loop six-legged robot to dynamically run into a large bump of varying height to discover the maximal traversal performance, and studied how locomotor modes and traversal performance are affected by body-terrain interaction. Remarkably, during rapid running, both the animal and the robot were capable 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 approached the bump with a low initial body yaw and a high initial body pitch, and why deflection was more likely otherwise. Inspired by these principles, we demonstrated a novel control strategy of active body pitching that increased the robot maximal traversable bump height by 75%. Our study is a major step in establishing the framework of locomotion energy landscapes to understand locomotion in complex 3-D terrains.