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  • This is Pleurobot.

  • Pleurobot is a robot that we designed to closely mimic a salamander species

  • called Pleurodeles waltl.

  • Pleurobot can walk, as you can see here,

  • and as you'll see later, it can also swim.

  • So you might ask, why did we design this robot?

  • And in fact, this robot has been designed as a scientific tool for neuroscience.

  • Indeed, we designed it together with neurobiologists

  • to understand how animals move,

  • and especially how the spinal cord controls locomotion.

  • But the more I work in biorobotics,

  • the more I'm really impressed by animal locomotion.

  • If you think of a dolphin swimming or a cat running or jumping around,

  • or even us as humans,

  • when you go jogging or play tennis,

  • we do amazing things.

  • And in fact, our nervous system solves a very, very complex control problem.

  • It has to coordinate more or less 200 muscles perfectly,

  • because if the coordination is bad, we fall over or we do bad locomotion.

  • And my goal is to understand how this works.

  • There are four main components behind animal locomotion.

  • The first component is just the body,

  • and in fact we should never underestimate

  • to what extent the biomechanics already simplify locomotion in animals.

  • Then you have the spinal cord,

  • and in the spinal cord you find reflexes,

  • multiple reflexes that create a sensorimotor coordination loop

  • between neural activity in the spinal cord and mechanical activity.

  • A third component are central pattern generators.

  • These are very interesting circuits in the spinal cord of vertebrate animals

  • that can generate, by themselves,

  • very coordinated rhythmic patterns of activity

  • while receiving only very simple input signals.

  • And these input signals

  • coming from descending modulation from higher parts of the brain,

  • like the motor cortex, the cerebellum, the basal ganglia,

  • will all modulate activity of the spinal cord

  • while we do locomotion.

  • But what's interesting is to what extent just a low-level component,

  • the spinal cord, together with the body,

  • already solve a big part of the locomotion problem.

  • You probably know it by the fact that you can cut the head off a chicken,

  • it can still run for a while,

  • showing that just the lower part, spinal cord and body,

  • already solve a big part of locomotion.

  • Now, understanding how this works is very complex,

  • because first of all,

  • recording activity in the spinal cord is very difficult.

  • It's much easier to implant electrodes in the motor cortex

  • than in the spinal cord, because it's protected by the vertebrae.

  • Especially in humans, very hard to do.

  • A second difficulty is that locomotion is really due to a very complex

  • and very dynamic interaction between these four components.

  • So it's very hard to find out what's the role of each over time.

  • This is where biorobots like Pleurobot and mathematical models

  • can really help.

  • So what's biorobotics?

  • Biorobotics is a very active field of research in robotics

  • where people want to take inspiration from animals

  • to make robots to go outdoors,

  • like service robots or search and rescue robots

  • or field robots.

  • And the big goal here is to take inspiration from animals

  • to make robots that can handle complex terrain --

  • stairs, mountains, forests,

  • places where robots still have difficulties

  • and where animals can do a much better job.

  • The robot can be a wonderful scientific tool as well.

  • There are some very nice projects where robots are used,

  • like a scientific tool for neuroscience, for biomechanics or for hydrodynamics.

  • And this is exactly the purpose of Pleurobot.

  • So what we do in my lab is to collaborate with neurobiologists

  • like Jean-Marie Cabelguen, a neurobiologist in Bordeaux in France,

  • and we want to make spinal cord models and validate them on robots.

  • And here we want to start simple.

  • So it's good to start with simple animals

  • like lampreys, which are very primitive fish,

  • and then gradually go toward more complex locomotion,

  • like in salamanders,

  • but also in cats and in humans,

  • in mammals.

  • And here, a robot becomes an interesting tool

  • to validate our models.

  • And in fact, for me, Pleurobot is a kind of dream becoming true.

  • Like, more or less 20 years ago I was already working on a computer

  • making simulations of lamprey and salamander locomotion

  • during my PhD.

  • But I always knew that my simulations were just approximations.

  • Like, simulating the physics in water or with mud or with complex ground,

  • it's very hard to simulate that properly on a computer.

  • Why not have a real robot and real physics?

  • So among all these animals, one of my favorites is the salamander.

  • You might ask why, and it's because as an amphibian,

  • it's a really key animal from an evolutionary point of view.

  • It makes a wonderful link between swimming,

  • as you find it in eels or fish,

  • and quadruped locomotion, as you see in mammals, in cats and humans.

  • And in fact, the modern salamander

  • is very close to the first terrestrial vertebrate,

  • so it's almost a living fossil,

  • which gives us access to our ancestor,

  • the ancestor to all terrestrial tetrapods.

  • So the salamander swims

  • by doing what's called an anguilliform swimming gait,

  • so they propagate a nice traveling wave of muscle activity from head to tail.

  • And if you place the salamander on the ground,

  • it switches to what's called a walking trot gait.

  • In this case, you have nice periodic activation of the limbs

  • which are very nicely coordinated

  • with this standing wave undulation of the body,

  • and that's exactly the gait that you are seeing here on Pleurobot.

  • Now, one thing which is very surprising and fascinating in fact

  • is the fact that all this can be generated just by the spinal cord and the body.

  • So if you take a decerebrated salamander --

  • it's not so nice but you remove the head --

  • and if you electrically stimulate the spinal cord,

  • at low level of stimulation this will induce a walking-like gait.

  • If you stimulate a bit more, the gait accelerates.

  • And at some point, there's a threshold,

  • and automatically, the animal switches to swimming.

  • This is amazing.

  • Just changing the global drive,

  • as if you are pressing the gas pedal

  • of descending modulation to your spinal cord,

  • makes a complete switch between two very different gaits.

  • And in fact, the same has been observed in cats.

  • If you stimulate the spinal cord of a cat,

  • you can switch between walk, trot and gallop.

  • Or in birds, you can make a bird switch between walking,

  • at a low level of stimulation,

  • and flapping its wings at high-level stimulation.

  • And this really shows that the spinal cord

  • is a very sophisticated locomotion controller.

  • So we studied salamander locomotion in more detail,

  • and we had in fact access to a very nice X-ray video machine

  • from Professor Martin Fischer in Jena University in Germany.

  • And thanks to that, you really have an amazing machine

  • to record all the bone motion in great detail.

  • That's what we did.

  • So we basically figured out which bones are important for us

  • and collected their motion in 3D.

  • And what we did is collect a whole database of motions,

  • both on ground and in water,

  • to really collect a whole database of motor behaviors

  • that a real animal can do.

  • And then our job as roboticists was to replicate that in our robot.

  • So we did a whole optimization process to find out the right structure,

  • where to place the motors, how to connect them together,

  • to be able to replay these motions as well as possible.

  • And this is how Pleurobot came to life.

  • So let's look at how close it is to the real animal.

  • So what you see here is almost a direct comparison

  • between the walking of the real animal and the Pleurobot.

  • You can see that we have almost a one-to-one exact replay

  • of the walking gait.

  • If you go backwards and slowly, you see it even better.

  • But even better, we can do swimming.

  • So for that we have a dry suit that we put all over the robot --

  • (Laughter)

  • and then we can go in water and start replaying the swimming gaits.

  • And here, we were very happy, because this is difficult to do.

  • The physics of interaction are complex.

  • Our robot is much bigger than a small animal,

  • so we had to do what's called dynamic scaling of the frequencies

  • to make sure we had the same interaction physics.

  • But you see at the end, we have a very close match,

  • and we were very, very happy with this.

  • So let's go to the spinal cord.

  • So here what we did with Jean-Marie Cabelguen

  • is model the spinal cord circuits.

  • And what's interesting is that the salamander

  • has kept a very primitive circuit,

  • which is very similar to the one we find in the lamprey,