A robot inspired by how turtle hatchlings move in sand is helping to overcome underground locomotion hurdles.

A team of roboticists and engineers at the University of California San Diego (UCSD) developed the robot to progress the potential for sand locomotion - a material that is particularly challenging for robots. This is because of the friction between sand grains that leads to heavy and resistant forces on robots, difficulty to sense obstacles, and the fact that sand can switch between behaving like a liquid and a solid depending on many factors such as tide times and rainfall.

The team believed that observing animals would be key to developing a robot that can burrow, swim in, and dig itself out of sand. Inspiration came from sea turtle hatchlings, which have enlarged front fins that allow them to dig through the sand after emerging from their eggs. The research team at UCSD conducted extensive simulations and testing, finally landing on a tapered body design and a shovel-shaped nose.

The robot can travel in sand at a depth of five inches and at a speed of four meters per hour - mimicking the speed of other subterranean animals like worms and clams. The turtle-like flippers generate large propulsive forces, allowing the robot to steer, and is equipped with force sensors at the end of its limbs that allow it to detect obstacles while in motion and can operate remotely while being controlled via WiFi.

The potential benefits of solving locomotion in sand include inspecting grain silos, measuring soil contaminants, seafloor digging, extraterrestrial exploration, and search and rescue.

“We needed to build a robot that is both strong and streamlined,” said Shivam Chopra, lead author of the research paper and a Ph.D. student at the Jacobs School of Engineering at UCS.

The bot detects obstacles by monitoring changes in the torque generated by the movement of its flippers. It can detect obstacles above its body, but not below or directly in front of it. To keep the robot at a level depth in the sand, researchers designed two foil-like surfaces, which they call terrafoils, on the sides of the bot’s nose which allows them to control lift.

The research team tested the robot in a 5ft long tank in a UCSD laboratory and at La Jolla Shores, a beach near the UCSC campus. The next steps for the research team include increasing the robot’s speed and adapting it to burrow into and dig out of sand.