Robot turtle gives clues to locomotion on sand

Mechanics of movement key to developing multi-terrain robots

A turtle-inspired robot, dubbed FlipperBot, has helped physicists understand how animals walk on sand. Researchers at the Georgia Institute of Technology said that the work could help to develop multi-terrain robots that can swim in water and run on land using the same limbs.

The robot is 19 cm long, weighs 790g and is propelled by two flippers that span 40 cm. Each of the flipper limbs is driven by two servomotors and has different operating modes to simulate a fixed or rotating wrist. The researchers studied the mechanics of the robot's movement as it travelled across a bed of poppy seeds.

To do this they measured the depth that the flippers penetrated the poppy seeds and analysed this with measurements of body lift and drag, and flipper thrust taken at the same time.

One of the study's authors, Professor Daniel Goldman said: “Flipperbot allowed us to explore aspects of the sea turtle's gait and structure that were challenging, if not impossible, to investigate in field experiments using actual animals.”

He added: “When the robot was fitted with a free wrist, it was able to move more effectively over the ground as it allowed the flipper to remain locked in place within a solid region of sand, and this disturbed less material during the forward thrust.”

Previous robots inspired by nature, such as the cockroach inspired hexapedal robot, can move well over hard or uneven surfaces but slow down when travelling over granular surfaces like sand that shift under foot.