March 25, 2014
Energy-Efficient Robot Inspired By Atlantic Razor Clam Dynamics
Lee Rannals for redOrbit.com - Your Universe Online
Scientists have built a robotic clam that is able to replicate how an Atlantic razor clam can burrow itself into the sea soil using very little energy.
The Atlantic razor clam is able to dig itself through sea soil at about 0.4 inches per second and can dig up to one-fourth of a mile using the amount of energy equivalent to a AA battery.
"The clam's trick is to move its shells in such a way as to liquefy the soil around its body, reducing the drag acting upon it," Amos Winter, the Robert N. Noyce Career Development Assistant Professor of Mechanical Engineering at MIT, said in a statement. "This means it requires much less force to pull its shell into the soil than it would when moving through static soil."
The researchers created the RoboClam based on the Atlantic razor clam’s unique ability to dig. They said this device could be used to dig itself into the ground to bury anchors or destroy underwater mines that are still in hiding.
In order to enable the RoboClam to dig, the MIT researchers had to understand how the clam’s movement causes the soil to liquefy around its shell. According to the findings, when the razor clam begins to dig, it first retracts its shell, releasing the stress between its body and the soil around it. This causes the soil to begin collapsing and creates a localized landslide around the animal.
The team said that if the clam were to move its shell too slowly, the sand particles would collapse around the animal, and if it moves too quickly, it would not give the sand particles enough time to mix with the water flowing past.
"Our data showed that there was a very abrupt transition from being able to fluidize the soil to not moving the soil particles at all," Winter says.
The researchers built a mechanical puppet clamshell consisting of two halves that move together and apart in a similar way to an accordion. The puppet clam is connected to a rod, which opens and closes the shell and pushes it up and down. This method allows the RoboClam to create the same contractions that the Atlantic razor clam is able to achieve.
The team used a compressed air system to power the expansion and contraction of the shells when testing it in salt water. They are now developing an electronic version that will make it compatible to use with underwater vehicles.
"You might be operating these vehicles in a current, and need them to be stationary — for example, to monitor a biological situation, or for military purposes," Winter says. "You wouldn't want the vehicle constantly spinning its propellers in order to stay in one place because that just wastes energy, so it would be nice if you could just deploy an anchor and maintain your position without expending any energy."
The team reported their findings in the journal Bioinspiration and Biomimetics.