At NASA’s Jet Propulsion Laboratory, a multipurpose robot that could independently map, travel, and explore previously unreachable locations is being tested.
How do you build a robot that can autonomously explore unknown territory without real-time human guidance? A team at NASA’s Jet Propulsion Laboratory is tackling the issue of building a snake-like robot for navigating rough terrain with the mindset of a startup: build rapidly, test frequently, learn, change, repeat.
Exobiology Extant Life Surveyor, also known as EELS, is a self-propelled, autonomous robot that was developed with the goal of exploring geyser-emitting cracks in the surface of Saturn’s moon Enceladus to search for indications of life beneath its ice crust. A very adaptive robot has been created by designing for such a difficult environment, even if testing and development are ongoing. EELS could safely navigate a broad range of terrain, including undulating sand and ice, rock walls, craters too high for rovers, subterranean lava tubes, and labyrinthine areas beneath glaciers, on Earth, the Moon, and far beyond.
Team members from JPL test a snake robot called EELS at a ski resort in the Southern California mountains in February. Designed to sense its environment, calculate risk, travel, and gather data without real-time human input, EELS could eventually explore destinations throughout the solar system. Credit: NASA/JPL-Caltech
The robot has been tested in sand, snow and freezing conditions, including a local indoor ice rink, the Mars Yard at JPL, and a ‘robot playground’ built at a ski resort in Southern California’s snowy mountains.
Hiro Ono, the principle investigator on EELS at JPL, remarked, “We have a different mindset of robot development than traditional spacecraft, with numerous short cycles of testing and correcting. There are several textbooks on four-wheel vehicle design, but none on how to create an autonomous snake robot that will bravely travel where no robot has gone before. We must create our own. That is what we are now doing.
JPL’s EELS (Exobiology Extant Life Surveyor) was conceived of as an autonomous snake robot that would descend narrow vents in the icy crust of Saturn’s moon Enceladus to explore the ocean hidden below. But prototypes of have been put to the test to prepare the robot for a variety of environments. Credit: NASA/JPL-Caltech
How EELS Thinks and Moves
Due to the communications delay between Earth and outer space, EELS is built to independently detect its surroundings, decide its risk level, navigate, and collect data using as-yet-undetermined research instruments. The robot should be able to fix itself when something goes wrong without human intervention.
“Consider an automobile that is autonomously driving in an area without any traffic lights, stop signs, or even any roadways. The project’s autonomy head, Rohan Thakker, explained that the robot must determine what the route is and attempt to follow it. Then, it must descend a 100-foot plunge without falling.
Four stereo camera pairs and lidar, which is comparable to radar but uses brief laser pulses rather than radio waves to detect objects, are used by EELS to produce a 3D map of its surroundings. Navigation algorithms choose the most secure course of action using the data from those sensors. The objective has been to develop a library of “gaits,” or different ways the robot might move in response to topographical problems, ranging from sidewinding to curling in on itself, a manoeuvre the team refers to as “banana.”
The robot will have 48 actuators—basically tiny motors—in its finished form, giving it the ability to take on various shapes but adding complexity for both the hardware and software teams. The actuators are compared by Thakker as “48 steering wheels.” Many of them contain integrated force-torque sensing, which functions as a type of skin allowing EELS to sense how much force it is applying to the ground. By positioning itself to push against opposing walls at the same moment, it can manoeuvre vertically through small chutes with uneven surfaces, much like a rock climber.
When they slid the robot’s perceiving head, the portion with the cameras and lidar, into a vertical shaft known as a moulin at Athabasca Glacier in the Canadian Rockies last year, the EELS team had the opportunity to encounter these types of difficult environments. They will return to the area in September with a robot modified to test subsurface mobility, which is in many respects like to frozen moons in our solar system. To monitor the chemical and physical characteristics of glaciers, the team will drop a tiny sensor suite that EELS will eventually be able to deploy to far-off locations.
At some point, Robinson stated, “we’ll look at what science instruments we can integrate with EELS,” adding that “our focus so far has been on autonomous capability and mobility.” “Scientists tell us where they want to go and what makes them most enthusiastic, and we’ll give them a robot to go there. How? We just need to construct it, just like a company.”
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