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dc.contributor.authorLi, Chenen_US
dc.contributor.authorUmbanhowar, Paul B.en_US
dc.contributor.authorKomsuoglu, Haldunen_US
dc.contributor.authorKoditschek, Daniel E.en_US
dc.contributor.authorGoldman, Daniel I.en_US
dc.date.accessioned2013-04-09T20:08:38Z
dc.date.available2013-04-09T20:08:38Z
dc.date.issued2009-03-03
dc.identifier.citationChen Li, Paul B. Umbanhowar, Haldun Komsuoglu, Daniel E. Koditschek, and Daniel I. Goldman, “Sensitive dependence of the motion of a legged robot on granular media,” PNAS, 106 no. 9, 3029-3034 (March 3, 2009)en_US
dc.identifier.issn1091-6490
dc.identifier.urihttp://hdl.handle.net/1853/46703
dc.description© 2009 by the National Academy of Sciencesen_US
dc.descriptionDOI:10.1073/pnas.0809095106en_US
dc.description.abstractLegged 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 φ and the limb frequency ω, and a dramatic transition from rotary walking to slow swimming occurs when φ becomes small enough and/or ω large enough. We propose a kinematic model of the rotary walking mode based on generic features of penetration and slip of a curved limb in granular media. The model captures the dependence of robot speed on limb frequency and the transition between walking and swimming modes but highlights the need for a deeper understanding of the physics of granular media.en_US
dc.publisherGeorgia Institute of Technologyen_US
dc.subjectBioinspired roboticsen_US
dc.subjectRobotic gaiten_US
dc.subjectLocomotion on complex terrainen_US
dc.subjectVolume fractionen_US
dc.subjectSanden_US
dc.titleSensitive dependence of the motion of a legged robot on granular mediaen_US
dc.typePre-printen_US
dc.contributor.corporatenameGeorgia Institute of Technology. School of Physicsen_US
dc.contributor.corporatenameUniversity of Pennsylvania. Dept. of Electrical and Systems Engineeringen_US
dc.contributor.corporatenameNorthwestern University. Dept. of Mechanical Engineering,en_US
dc.publisher.originalNational Academy of Sciencesen_US
dc.identifier.doi10.1073/pnas.0809095106


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