Agile Legged Locomotion in
Reconfigurable Modular Robots

Agile Legged Locomotion in
Reconfigurable Modular Robots

Chen Yu1 David Matthews1 Jingxian Wang1 Jing Gu1 Douglas Blackiston2, 3 Michael Rubenstein1 Sam Kriegman1
1Center for Robotics and Biosystems, Northwestern University
2Dept. of Biology, Tufts University
3Wyss Institute for Biologically Inspired Engineering, Harvard University

Significance

All legged robots deployed “in the wild” to date were given a body plan that was predefined by human designers and could not be redefined in situ. The manual and permanent nature of this process has resulted in very few species of agile terrestrial robots beyond familiar four-limbed forms. Here we introduce highly athletic modular building blocks and show how they enable the automatic design and rapid assembly of novel agile robots that can “hit the ground running” in unstructured outdoor environments. This suggests that others may adopt this approach to synthesize and study adaptive behaviors in the field using morphologies that emerge from the demands of the environment rather than prior assumptions.

Abstract

Legged machines are becoming increasingly agile and adaptive but they have so far lacked the morphological diversity of legged animals, which have been rearranged and reshaped to fill millions of niches. Unlike their biological counterparts, legged machines have largely converged over the past decade to canonical quadrupedal and bipedal architectures that cannot be easily reconfigured to meet new tasks or recover from injury. Here we introduce autonomous modular legs: agile yet minimal, single-degree-of-freedom jointed links that can learn complex dynamic behaviors and may be freely attached to form multilegged machines at the meter scale. This enables rapid repair, redesign, and recombination of highly-dynamic modular agents that move quickly and acrobatically (non-quasistatically) through unstructured environments. Because each module is itself a complete agent, the bodies that contain them can sustain deep structural damage that would completely disable other legged robots. We also show how to encode the vast space of possible body configurations into a compact latent design space that can be efficiently explored, revealing a wide diversity of novel legged forms.

Videos

Reconfigurable robots in the wild. Reconfigurable legged robots behave autonomously across sand, mud, grass, tree roots, plant litter, mulch, gravel, bricks, concrete, and combinations thereof.
Acrobatic behaviors and resilience to damage. Robots behave, resist adversarial perturbations, and withstand body-altering damage. Control policies use internal sensing only; motion capture was not supplied to the policy, it is used only for behavioral analyses.