Six-legged machine runs across grainy surfaces

By Meghan Rosen

Web edition: March 22, 2013

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A LEG UP

A hexapod robot rests in a bed of granular material. The robot uses custom-designed legs to move quickly over pebbly surfaces.

Credit: Courtesy of Chen Li, Tingnan Zhang, Daniel Goldman

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A tricked-out robot can scurry quickly over pebbly surfaces using custom-made legs.

A commercially available, build-it-yourself toy robot called the RoboXplorer was the starting point for physicists led by Daniel Goldman of Georgia Tech. They turbocharged the toy by slapping on plastic legs that plow through grainy soils. The work could help engineers speed up other legged bots and even wheeled devices, such as the Mars rovers, the researchers suggest in the March 22 Science.

Scientists have previously made machines that travel across solid ground and sail through air and water, but had trouble getting robots to trek over sand — a slippery substance that can pack firmly like earth or flow freely like water.

By measuring forces on model legs pushed through “sand” made of glass beads or poppy seeds, the team figured out the best leg design for running over gravelly ground. Spinning C-shaped legs helped the bot zip across a bed of poppy seeds.

C-shaped legs help a modified toy robot dash over a bed of sand.
Credit: Courtesy of Chen Li, Tingnan Zhang, Daniel Goldman