Science! NASA builds snake-like robots to explore the ocean and ice sheets

In recent years, Enceladus has attracted much attention due to the fact that it contains an ocean system beneath its surface ice.

In a 17-year collaboration, researchers at Carnegie Mellon University (CMU) and NASA's Jet Propulsion Laboratory have created an autonomous, snake-like robot , the Exobiology Extant Life Surveyor (EELS).

NASA scientists said they hope to use the EELS robot to search for signs of life in the ocean beneath the icy crust of Enceladus. The related paper was also published in Science Robotics and was featured on the cover of the March issue.

Snake robots have always been considered the first choice for activities in narrow and complex environments. Compared with traditional robots, they can move freely in areas with many obstacles with their slender bodies with dozens of hinged joints.

After several years of preparation, EELS brings together the wisdom of many universities including Carnegie Mellon University, Arizona State University and University of California, San Diego, and demonstrates the most cutting-edge robotics technology.

EELS is about 4 meters long and consists of 10 identical parts, with a total weight of about 100 kilograms. Each section contains 3 actuators, the first two are used to adjust the shape, and the last one controls the advancement of the surface thread. Each shape actuator can provide a peak torque of up to 400N·m, giving EELS a wide range of degrees of freedom.

The unique self-repeating structure gives EELS excellent mobility. It can avoid obstacles by means of serpentine twists and turns, and can also quickly cross flat areas through active skin thread propulsion.

Looking at the system architecture of EELS, its control module adopts a layered architecture, which helps to disassemble complex problems and maintain code. The control level rises from the bottom-level hardware instructions to the high-level task goals, and each level controller decomposes and translates the intentions of the previous level. For example, the actuator controller will convert the screw speed, shape, etc. required by the upper level into specific actions that can be executed by the hardware.

According to Professor Howie Choset, a research scientist on the project, "The benefit of snake robots is that they can use their many joints and slender physiques to move through tightly packed volumes and reach locations that robotic operatives cannot reach."

Even in extreme environments such as ice, sand, rocks, cliffs, etc., EELS can still pass freely. EELS will also use these capabilities to crawl into the cracks of Enceladus' ice layer, which will help the robot move better on the ice until it finds a crack or geyser hole to crawl into.

In addition, the "wheels" of EELS are also very special. Unlike other snake-like robots, it is more like a "bottle opener" than a "wheel".

"As these corkscrews rotate, they penetrate the ice a little bit, but also enable the mechanism to roll forward. So the robot has the ability to propel itself, not only with a serpentine motion, but these corkscrew wheels allow it to move across icy surfaces very quickly."