Flipperbot Helps Researchers Understand Turtle Locomotion
April 24, 2013

Flipperbot Offers Insight Into Turtle Locomotion On Sand

Watch the video "Using Robots to Reveal Walking Secrets of Baby Sea Turtles"

Brett Smith for redOrbit.com - Your Universe Online

In recent years, robotics engineers have increasingly looked to nature for inspiration. Now, a trio of American scientists has developed a sea turtle-like robot to help them learn about the mechanics behind walking on sand-like surfaces.

Named “Flipperbot,” the robot was described recently in the journal“¯Bioinspiration and Biomimetics by Georgia Institute of Technology researchers Daniel Goldman, Nicole Mazouchova and Paul Umbanhowar from Northwestern University.

The team said their creation could not only assist in learning about locomotion but also about the evolution of the appendages that allow turtles and seals to move about.

"We are looking at different ways that robots can move about on sand," said Daniel Goldman, a physics professor at the Georgia Institute of Technology. "We wanted to make a systematic study of what makes flippers useful or effective. We've learned that the flow of the materials plays a large role in the strategy that can be used by either animals or robots."

Work on the Flipperbot began in 2010 with a six-week study of hatchling sea turtles. During the study, Mazouchova studied the baby turtles´ movements along track covered with beach sand as they moved toward artificial moonlight. She found that the hatchlings were able to maintain their speed regardless of the type of surface they were moving on, hard or soft.

"On soft sand, the animals move their limbs in such a way that they don't create a yielding of the material on which they're walking," Goldman said. "That means the material doesn't flow around the limbs and they don't slip. The surprising thing to us was that the turtles had comparable performance when they were running on hard ground or soft sand."

The scientists found that wrist-control is a key ability in moving on different types of surfaces.

"On hard ground, their wrists locked in place, and they pivoted about a fixed arm," Goldman explained. "On soft sand, they put their flippers into the sand and the wrist would bend as they moved forward. We decided to investigate this using a robot model."

The scientists used this knowledge in their design of Flipperbot, which is about 7.5 inches“¯in length and weighs about two pounds.

"In the robot, the free wrist does provide some advantage," Goldman said. "For the most part, the wrist confers advantage for moving forward without slipping. The wrist flexibility minimizes material yielding, which disturbs less ground. The flexible wrist also allows both the robot and turtles to maintain a high angle of attack for their bodies, which reduces performance-impeding drag from belly friction."

Goldman noted that the robot will aid the work of both engineers and biologists alike.

"This work can provide fundamental information on what makes flippers good or bad,” he said. “This information could give robot designers clues to appendage designs and control techniques for robots moving in these environments."

"To understand the mechanics of how the first terrestrial animals moved, you have to understand how their flipper-like limbs interacted with complex, yielding substrates like mud flats," Goldman added. "We don't have solid results on the evolutionary questions yet, but this certainly points to a way that we could address these issues."