RoboClam' hits new depths as robotic digger

Mechanical engineers from MIT have developed a digging robot that can burrow through soil while expending very little energy

The Atlantic razor clam is a mollusc that is found exclusively along the coast of North America. Estimates based on the creature's size, strength and shape all suggest it should only be able to burrow a few centimetres, but they can actually bury through undersea soil at the rate of about 1cm per minute down to about 70cm.

This remarkable show of strength from the little clam requires only the amount of energy contained in an AA battery. As the clam's outer shell opens and closes, it exerts pressure on the surrounding soil, turning it from a solid to a liquid, which means there is much less resistance. It's a nifty trick that's achieved by first retracting the shell slightly in order to release the pressure on itself. As it continues to contract, more water is sucked into the immediate area around it and mingles with the soil, forming quicksand that is easier to move through -- although the whole manoeuvre has to be very carefully timed, to make sure the clam moves when the quicksand is at the right density.

RoboClam consists of two pneumatic pistons, which power a 9cm-long motor and mimic the razor clam's shell. It is operated according to a "genetic algorithm", which causes the robot to record every movement for learning purposes. This means the more the RoboClam is used, the more it learns and develops good behavioural habits, just like any other slowly evolving organisms.

RoboClam could have a variety of applications including anchoring underwater robots (MIT is also currently developing underwater robots with a company called Bluefin Robotics) installing cables under the sea or neutralising mines.

The MIT researchers tested RoboClam in the Atlantic razor clam's natural environment and over the course of 300 tests proved that the robot was almost a efficient at digging as the razor clam itself.

"We have demonstrated that the robot is able to burrow into the soil with the same energy and depth relationship as the animal. Moving through static soil requires burrowing energy that scales with the square of depth," said Professor Amos Winter , the paper's lead author. "By fluidising soil and reducing drag, razor clams and the RoboClam can burrow with energy that scales linearly with depth."