A multi-legged robot traverses heterogeneous 3-D terrain via locomotor transitions*

Robots still struggle to traverse heterogeneous 3-D terrain cluttered with a variety of large obstacles. In contrast, small animals like cockroaches excel at doing so by using and controlling physical interaction with the terrain. Our recent research studied distinct locomotor challenges abstracted from such terrain—traversing large bumps, gaps, pillars, and flexible beams, and self-righting—and discovered strategies to overcome them (Othayoth et al. 2020, Proc. Roy. Soc. B). Here, we developed a multi-legged robot to integrate these strategies. A streamlined body shape enabled pillar traversal by passive obstacle repulsion and helped beam traversal by enhancing body rolling into gaps. Two active wings enabled self-righting by lifting the center of mass and reducing roll stability. An active tail facilitated bump traversal by pitching the body up using inertial effect, aided beam traversal by pushing against the ground to roll the body, and assisted self-righting by lateral perturbation. The robot traversed a bump of 2.5× hip height, pillars spaced 1.1× body width, and beams spaced 0.7× body width and self-righted within 4 s. We also developed a multi-body dynamics simulation of the physical robot and will use them to study sensory feedback principles for autonomous transitions.