As a quick jog on the beach reveals, running across sand is a lot different than running on a solid surface. So scientists are trying to design robots that scamper across granular materials as quickly as they would on terra firma. In new lab tests, a 13-centimeter-long, 150-gram robot equipped with legs of various shapes dashed across sand, pebbles, glass spheres, and poppy seeds (seen in the video above). Test results enabled researchers to develop equations that help predict the robot's motion, including how fast it would move across the surface or whether it would bog down unless it maintained a certain rate of speed. Besides helping engineers design rovers or reconnaissance robots that can readily negotiate granular sand dunes or snow banks, the new models might help biomechanicists better understand how animals move through such environments, the researchers report online today in Science. The models might even help paleontologists more accurately interpret sets of footprints once made in shifting surfaces but now preserved in sandstones or mudstones.
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