From the Cover: Sensitive dependence of the motion of a legged robot on granular media |
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| Authors: | Chen Li Paul B. Umbanhowar Haldun Komsuoglu Daniel E. Koditschek Daniel I. Goldman |
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| Affiliation: | aSchool of Physics, Georgia Institute of Technology, Atlanta, GA 30332; ;bDepartment of Mechanical Engineering, Northwestern University, Evanston, IL 60208; and ;cDepartment of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA 19104 |
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| Abstract: | Legged locomotion on flowing ground (e.g., granular media) is unlike locomotion on hard ground because feet experience both solid- and fluid-like forces during surface penetration. Recent bioinspired legged robots display speed relative to body size on hard ground comparable with high-performing organisms like cockroaches but suffer significant performance loss on flowing materials like sand. In laboratory experiments, we study the performance (speed) of a small (2.3 kg) 6-legged robot, SandBot, as it runs on a bed of granular media (1-mm poppy seeds). For an alternating tripod gait on the granular bed, standard gait control parameters achieve speeds at best 2 orders of magnitude smaller than the 2 body lengths/s (≈60 cm/s) for motion on hard ground. However, empirical adjustment of these control parameters away from the hard ground settings restores good performance, yielding top speeds of 30 cm/s. Robot speed depends sensitively on the packing fraction ![[var phi]](corehtml/pmc/pmcents/x03C6.gif "/> and the limb frequency ω, and a dramatic transition from rotary walking to slow swimming occurs when <img src=") | |
| Keywords: | bioinspired robotics robotic gait locomotion on complex terrain volume fraction sand |
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