Crustacean-inspired excavator robot

Robots have achieved a high degree of mobility moving on the earth’s surface, on and under water, in the air and in space. However, very little progress has been made by going underground, that is digging and moving through the earth or sand.

There are animals, such as earthworms, moles and some crustaceans, that spend a good part of their time underground and that advance through it by burrowing. Scientists have been inspired by one of these animals to create a small robot that essentially does the same thing.

The team of Laura Treers and Hannah Stuart, from the University of California at Berkeley, United States, has been inspired by the crustacean of the Emerita analoga species to create and test one of the first legged robots that can bury itself vertically. This excavating robot, called EMBUR (EMerita BUrrowing Robot), uses an innovative leg design to achieve a downward movement that emulates the way in which this crustacean buries itself in the sand on the beach.

Advancing vertically sinking into terrain, even loose sand, is difficult. The deeper an animal (or robot) digs, the more force the grains exert, making it harder and harder to dig.

To overcome this challenge, the researchers designed the robot’s legs in such a way that they would experience a much greater force in one direction than another. Like a swimmer, this robot’s legs expand to exert large forces during the forward stroke, but fold and retract during the return stroke.

The EMBUR robot burying itself on a test floor in Hannah Stuart’s lab. (Photo: Adam Lau/Berkeley Engineering)

There has been some progress recently in creating anisotropic legs for granular media, but Treers says this is the first time they have been successfully implemented on such a robot.

Treers and his colleagues also had to devise a way to prevent grains of sand from entering the EMBUR’s mechanisms and jamming them. Again they were inspired by the crustacean Emerita analoga.

The research team created a cuticle, which is analogous to a membrane found in those crustaceans. It is a soft and flexible material that covers the openings of the joints to prevent the grains from entering inside, but that allows the free movement of said joints.

The new robot, or derivatives of it, could one day be used in various industries and areas of study. Among its applications are the measurement of the quality of the soil of possible agricultural sites, geotechnical engineering, the collection of data from the seabed, as well as countless tasks that include excavation and construction. In addition, they could serve as small deployable anchors from marine vehicles or from rovers circulating in otherworldly terrain.

Treers and his colleagues expose the technical details of their EMBUR robot in the academic journal Frontiers in Robotics and AI, under the title “Mole crab-inspired vertical self-burrowing.” (Font: NCYT by Amazings)