How to make a robot walk on Mars? It’s a steep challenge

From the inhabitant rover, which landed on Mars in 1997, at Perseverance, which landed in february, the robots of the red planet share a defining characteristic: the wheels. Riding is much more stable and energy efficient than walking, than even robots on Earth. struggle to master. After all, NASA would hate their dear Martian explorer to tip over and flip like a turtle on its back.

The problem with the wheels, however, is that they limit where rovers can go: to explore complicated Martian terra like craggy hills, you need the kind of legs that evolution has given animals on Earth. Thus, a team of scientists from ETH Zurich in Switzerland and the Max Planck Institute for Solar System Research in Germany played with a little quadrupedal robot called SpaceBok, designed to mimic an antelope known as the springbok.

True to its name, a real springbok bounces in the deserts of Africa, maybe to confuse predators. The original concept of the robot, introduced in 2018, was actually to jump on the surface of the moon, as the astronauts did to move in low lunar gravity. It may work on our satellite, where the landscape is relatively flat, but on Mars it’s probably too risky given the complex terrain, which is full of sand, rocks, and steep slopes. So now researchers are changing its limbs and gaits to see if it might be able to handle more brutal landscapes.

In these new experiments, the team programmed SpaceBok with more traditional and less elastic gaits. More precisely, the researchers wanted to compare two types: a “static” gait, in which at least three limbs come into contact with the ground at a given moment, and a “dynamic” gait, in which more than one limb can leave. the ground immediately. The first is more methodical, but the second is more efficient because it allows the robot to move faster.

The researchers also equipped versions of SpaceBok with two types of feet: point and planar. Pointed feet have a small area, much like the hoof of a real springbok. Flat feet, on the other hand, are actually flat pivoting circles, which bend at an angle when the foot makes contact with the ground. Think of them more like snowshoes than clogs. Or really, they are snowshoes with cleats, because they are studded with projections that help the foot to grip the ground.

Notice the large area of ​​the flat feet

Courtesy of Hendrik Kolvenbach / ETH Zurich

Once the researchers had different gait and foot configurations that they could use to customize the robot, they unleashed it into a giant tilted sandbox laden with materials that come close to the ground found on Mars. This way, they were able to test whether one of these configurations allowed the robot to climb a 25 degree plane. By monitoring the robot’s energy consumption, they were able to quantify the effectiveness of each of the gait and foot configurations.

In one new preprint describing the work, which has been accepted for publication in the journal Field robotics, they showed that the machine can deftly and efficiently climb a simulated Martian hill without rolling down it. “We wanted to show that with these dynamically functioning systems nowadays, they can actually walk on Martian sand,” says Hendrik Kolvenbach, roboticist at ETH Zurich, lead author of the study. “It’s a technology that has a lot of potential now for the future. “

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