It is the only robot that can move five inches deep in sand, and has a speed of 1.2 millimeters per second or around 4 meters (13 feet) per second. Although it may appear slow, this is equivalent to the speed of other underground creatures like worms and clams.
Shivam Chopra developed this robot, inspired by turtle hatchlings, as a Ph.D. student in the research group of Nicholas Gravish in the UC San Diego Department of Mechanical and Aerospace Engineering. Image Credit: University of California, San Diego
The robot has force sensors at the tips of each limb that enable it to sense impediments even while moving. Both WiFi and untethered operation are possible with it.
Robots that can travel in sand encounter several difficulties, such as dealing with stronger pressures than those experienced by airborne or subaquatic robots. They are also more prone to damage.
The investigation of grain silos, testing for soil toxins, drilling on the bottom, extraterrestrial exploration, and search and rescue are some possible advantages of resolving movement in the sand.
A team of roboticists at the University of California, San Diego created the robot as a consequence of several tests they ran to learn more about sand and how robots can move through it.
Sand presents unique challenges due to the high forces generated by friction between sand grains, the difficulty in detecting obstructions, and the fact that sand can act either as a liquid or a solid, depending on the situation.
The group thought that studying animals would be essential to creating a robot that could swim in the sand and dig itself out. They settled on sea turtle hatchlings, which have larger front fins that allow them to surface after hatching.
The robot can navigate with the help of its flippers, which resemble turtles, and they could also be able to detect impediments.
Scientists still do not completely comprehend how flipper-like robots can maneuver on the sand. After considerable testing and simulations, the research team at UC San Diego decided on a tapered body form with a shovel-shaped nose.
We needed to build a robot that is both strong and streamlined.
Shivam Chopra, Study Lead Author and Ph.D. Student, Jacobs School of Engineer, University of California, San Diego
The robot uses variations in the torque produced by the movement of its flippers to identify obstructions. Objects above its body can be detected, but not those right in front of or below it.
To keep the robot level in the sand, researchers created two foil-like coverings on the sides of the bot’s nose, which they named terrafoils. They were able to control the lift because the robot kept its nose pointing toward the surface.
The robot was tested in a 5-foot-long tank in the lab as well as at La Jolla Shores, a beach near the UC San Diego campus. They discovered that the robot slowed down when it encountered wet sand, which provided extra resistance.
The robot’s speed will be increased in the next stages, and it will also be given the ability to really burrow into sand in addition to digging itself out of it.
The research was funded in part by the Office of Naval Research and was published in the May 12th, 2023 issue of Advanced Intelligent Systems.
Journal Reference
Chopra, S., et al. (2023) Toward Robotic Sensing and Swimming in Granular Environments using Underactuated Appendages. Advanced Intelligent Systems. doi:10.1002/aisy.202200404.