Get a grip: inward dactyl motions improve efficiency of sideways-walking gait for an amphibious crab-like robot.

Crabs are adept at traversing natural terrains that are challenging for mobile robots. Curved dactyls are a characteristic feature to engage terrain for resisting wave forces in surf zones. Inward gripping motions at the onset of stance could increase stability.Here, we add inward gripping motions to the foot trajectories of walking gaits to determine the energetic costs and speed for our 12 DOF crab-like robot, Sebastian. Specifically, we compared two gaits in which the step size (stance length) was the same, but the swing trajectories were either triangular (to minimize trajectory length) or quadrilateral (in which the leg deliberately oversteps in order to perform a distributed inward grip (DIG). The resulting gripping quadrilateral gait significantly outperformed the non-gripping triangular gait on diverse terrains (hard linoleum, soft mats, and underwater sand), providing between 15% and 34% energy savings. Using this gait eliminates the advantage of spherical end effectors for slip reduction on hard linoleum, which may lead to a better understanding of how to use crab-like morphology for more efficient locomotion. Finally, we subjected the walking robot to lab-generated waves with wave height approximately 166% of the dactyl length. Both gaits enabled the robot to walk undisturbed by the waves. Taken together, these results suggest that impact trajectory will be key for future amphibious robots. Future work can provide deeper understanding of the relationships between dactyls, gaits, and substrates in biology and robots.© 2022 IOP Publishing Ltd.

Citation

Nicole Graf, John E Grezmak, Kathryn A Daltorio. Get a grip: inward dactyl motions improve efficiency of sideways-walking gait for an amphibious crab-like robot. Bioinspiration & biomimetics. 2022 Aug 04

PMID: 35926481

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