Cheetah-cub is a super-fast mammal-like quadruped robot. Image via Biorobotics Laboratory, EPFL
Robots might already be able to fight wars, make art, and win at rock-paper -scissors, but they’ve got a way to go when it comes to moving from point A to B over rough terrain. Your standard wheel-based bot might be fine on a flat floor, but put some mud, water, or rocks in its way and it’s about as good as a Dalek faced with a flight of stairs.
Researchers at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland are turning to the animal kingdom for inspiration on getting their robots moving, and in the process they’re helping to decode how the spinal cord works, and how animal movement evolved over the millennia from swimming to crawling to running.
A selection of their robots came over to London’s Science Museum over the weekend, as part of a “Robot Safari” display. The exhibition showcased biomimetic robots from across Europe, but EPFL was the most widely represented institution with four different bots for the public to see, including its Cheetah-cub, the fastest sub-30kg quadruped robot in the world.
Amphibot III is modeled on a lamprey. Image: Biorobotics Laboratory, EPFL
But cheetahs are pretty far along the chain of evolution. To begin their work in robo-evolution, the researchers started several steps prior with a robot modeled on the lamprey, a rather terrifying-looking fanged, snake-like fish. Their Amphibot achieves a primitive swimming motion similar to the lamprey, and can swim as fast as a human. It's largely thanks to the robot's backbone.
“What controls the robot is really a model of the lamprey spiral cord,” Auke Ijspeert, who leads the Biorobotics Laboratory, told me over the phone. “Not many people realise to what extent the spinal cord is really the most central part of the whole central nervous system for controlling locomotion (movement). You can almost locomote without other parts of the brain, like the fact that you can cut the head off a chicken and it can still run for a while.”
The Amphibot demonstrates that they understand the organisation of the lamprey spinal cord enough to see how it controls its movement—a step towards helping neuroscientists understand vertebrates' spinal cords more generally.
Salamandra Robotica II, a basic salamander robot. Image: Kostas Karakasiliotis, Biorobotics Laboratory, EPFL
Next up in their evolutionary tour was the salamander, a key animal from an evolutionary perspective.
“It’s an amphibian that is very similar to the first terrestrial vertebrates, so it’s an animal that can swim and walk, and interestingly again the spinal cord completely organises a swimming and walking gait,” explained Ijspeert.
Back in 2007, he and his colleagues published a paper in the journal Science that showed how adding another layer of control on top of the lamprey’s swimming circuits allowed the salamander’s spinal cord to transition from swimming to walking. Ijspeert suggests that this could be what happened during evolution to take animals from water to land.
Pleurobot was unveiled in London this weekend. Image: Biorobotics Laboratory, EPFL
They found the salamander so interesting that they made several robots based on the creature. Salamandra Robotica is a simple extension of the lamprey robot, with just one motor per limb, to show the basic transition from swimming to walking. Pleurobot, their latest, has twice the number of motors and moves a lot more like the actual animal.
In order to accurately mimic the lizard-like amphibians, the researchers collaborated with biologists to capture the animals’ different movements using an x-ray machine, so they could see in detail how the bones moved.
“So basically we had the best data possible explaining the salamander locomotion, and from that we could very carefully reconstruct a robot that could closely match this bone motion during different types of gaits—the swimming, the crawling, the walking,” said Ijspeert. Pleurobot is still in the making, and wasn’t able to swim on its London visit—it’s waiting for a waterproof suit.
Cheetah-cub is the fastest sub-30kg quadruped robot in the world, reaching 1.42m/s. Image: Biorobotics Laboratory, EPFL
From the salamander robots, it was a bit of an evolutionary leap to the Cheetah-cub and a first attempt at mammal-like locomotion. The biggest challenge for mammalian bots, Ijspeert explained, is maintaining balance: A cat is a lot higher from the ground than a salamander, and therefore more likely to fall over. Their cheetah prototype (which is basically a set of legs) mimics a mammal’s biomechanics, which makes controlling it a lot simpler.
“It’s kind of outsourcing the control problem to the mechanics, to the body,” said Ijspeert. “I like to call it the intelligence of the body; a mechanical intelligence which we tend to underestimate.”
Because the Cheetah-cub has the same limb structure as the animal, with robotic muscles and tendons that share the same properties, it handles a lot of the challenges related to movement in what can only be described as a “natural” way. The researcher has a controller but only gives simple directions—like left, right, and so on—and the robot’s spinal cord model, which is onboard in the form of microcontrollers or microprocessors, automatically transforms these into the many different signals required to complete the movement.
Watch Cheetah-cub go! Via Youtube/EPFL Biorobotics Laboratory
You can see where this is going: from lamprey to salamander to cheetah to, ultimately, human. Of course, human bipedal movement is much more complicated, but the principles remain the same.
“What we want to contribute to in the long run is to be able to design therapies of how you could kind of correct something that went wrong after a spinal cord injury,” said Ijspeert. For him, that sort of contribution to neuroscience is the main point of working with the robots. To investigate further, his lab has been working with the child-sized humanoid iCub, and now its adult successor COMAN.
Aside from the broader goal of scientific understanding, the robots have various practical applications. A spin-off project is looking at using the lamprey and salamander robots in search-and-rescue missions in collapsed buildings, especially where water is present. Equipping them with sensors could allow them to crawl and swim around looking for survivors or inspecting the building, without the need to put humans or rescue dogs at risk. Meanwhile, the Amphibot is also being use to monitor pollution in lakes.
The Jessiko robotic fish shows how robots can work together in a "shoal." Image: Robotswim
Among the other robots on show at the Science Museum was U-CAT, a robotic turtle that can inspect shipwrecks from the Tallinn University of Technology in Estonia, fish-like robots Jessiko and iTuna from Robotswim SARL in France and the Universidad Politécnica de Madrid in Spain, respectively, and a Bat-Bot also from Madrid.
Ijspeert sees a future quite literally crawling (and swimming and flying) with biomimetic robots helping us with exploration, transport, and rescue missions, but said there’s one sector he’s not keen on working with: the military.
“It’s purely civilian and I’d really like to keep it that way,” he said. “I think there’s a big risk of robotics getting a bad name, as we see with drones, for instance … I think there’s a big risk of going in completely the wrong direction.”
So for now, let's keep our biomimetic robots as pets and helpers, not predators.