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This is Pleurobot.
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Pleurobot is a robot that we designed
to closely mimic a salamander species
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called Pleurodeles waltl.
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Pleurobot can walk, as you can see here,
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and as you'll see later, it can also swim.
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So you might ask,
why did we design this robot?
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And in fact, this robot has been designed
as a scientific tool for neuroscience.
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Indeed, we designed it
together with neurobiologists
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to understand how animals move,
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and especially how the spinal cord
controls locomotion.
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But the more I work in biorobotics,
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the more I'm really impressed
by animal locomotion.
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If you think of a dolphin swimming
or a cat running or jumping around,
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or even us as humans,
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when you go jogging or play tennis,
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we do amazing things.
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And in fact, our nervous system solves
a very, very complex control problem.
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It has to coordinate
more or less 200 muscles perfectly,
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because if the coordination is bad,
we fall over or we do bad locomotion.
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And my goal is to understand
how this works.
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There are four main components
behind animal locomotion.
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The first component is just the body,
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and in fact we should never underestimate
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to what extent the biomechanics
already simplify locomotion in animals.
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Then you have the spinal cord,
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and in the spinal cord you find reflexes,
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multiple reflexes that create
a sensorimotor coordination loop
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between neural activity in the spinal cord
and mechanical activity.
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A third component
are central pattern generators.
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These are very interesting circuits
in the spinal cord of vertebrate animals
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that can generate, by themselves,
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very coordinated
rhythmic patterns of activity
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while receiving
only very simple input signals.
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And these input signals
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coming from descending modulation
from higher parts of the brain,
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like the motor cortex,
the cerebellum, the basal ganglia,
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will all modulate activity
of the spinal cord
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while we do locomotion.
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But what's interesting is to what extent
just a low-level component,
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the spinal cord, together with the body,
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already solve a big part
of the locomotion problem.
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You probably know it by the fact
that you can cut the head off a chicken,
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it can still run for a while,
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showing that just the lower part,
spinal cord and body,
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already solve a big part of locomotion.
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Now, understanding how this works
is very complex,
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because first of all,
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recording activity in the spinal cord
is very difficult.
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It's much easier to implant electrodes
in the motor cortex
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than in the spinal cord,
because it's protected by the vertebrae.
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Especially in humans, very hard to do.
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A second difficulty is that locomotion
is really due to a very complex
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and very dynamic interaction
between these four components.
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So it's very hard to find out
what's the role of each over time.
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This is where biorobots like Pleurobot
and mathematical models
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can really help.
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So what's biorobotics?
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Biorobotics is a very active field
of research in robotics
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where people want to
take inspiration from animals
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to make robots to go outdoors,
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like service robots
or search and rescue robots
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or field robots.
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And the big goal here
is to take inspiration from animals
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to make robots that can handle
complex terrain --
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stairs, mountains, forests,
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places where robots
still have difficulties
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and where animals
can do a much better job.
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The robot can be a wonderful
scientific tool as well.
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There are some very nice projects
where robots are used,
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like a scientific tool for neuroscience,
for biomechanics or for hydrodynamics.
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And this is exactly
the purpose of Pleurobot.
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So what we do in my lab
is to collaborate with neurobiologists
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like Jean-Marie Cabelguen,
a neurobiologist in Bordeaux in France,
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and we want to make spinal cord models
and validate them on robots.
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And here we want to start simple.
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So it's good to start with simple animals
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like lampreys, which are
very primitive fish,
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and then gradually
go toward more complex locomotion,
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like in salamanders,
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but also in cats and in humans,
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in mammals.
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And here, a robot becomes
an interesting tool
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to validate our models.
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And in fact, for me, Pleurobot
is a kind of dream becoming true.
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Like, more or less 20 years ago
I was already working on a computer
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making simulations of lamprey
and salamander locomotion
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during my PhD.
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But I always knew that my simulations
were just approximations.
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Like, simulating the physics in water
or with mud or with complex ground,
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it's very hard to simulate that
properly on a computer.
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Why not have a real robot
and real physics?
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So among all these animals,
one of my favorites is the salamander.
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You might as why,
and it's because as an amphibian,
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it's a really key animal
from an evolutionary point of view.
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It makes a wonderful link
between swimming,
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as you find it in eels or fish,
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and quadruped locomotion,
as you see in mammals, in cats and humans.
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And in fact, the modern salamander
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is very close to the first
terrestrial vertebrate,
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so it's almost a living fossil,
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which gives us access to our ancestor,
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the ancestor to all terrestrial tetrapods.
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So the salamander swims
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by doing what's called
an anguilliform swimming gait,
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so they propagate a nice traveling wave
of muscle activity from head to tail.
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And if you place
the salamander on the ground,
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it switches to what's called
a walking trot gait.
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In this case, you have nice
periodic activation of the limbs
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which are very nicely coordinated
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with this standing wave
undulation of the body,
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and that's exactly the gait
that you are seeing here on Pleurobot.
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Now, one thing which is very surprising
and fascinating in fact
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is the fact that all this can be generated
just by the spinal cord and the body.
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So if you take
a decerebrated salamander --
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it's not so nice
but you remove the head --
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and if you electrically
stimulate the spinal cord,
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at low level of stimulation
this will induce a walking-like gait.
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If you stimulate a bit more,
the gait accelerates.
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And at some point, there's a threshold,
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and automatically,
the animal switches to swimming.
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This is amazing.
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Just changing the global drive,
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as if you are pressing the gas pedal
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of descending modulation
to your spinal cord,
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makes a complete switch
between two very different gaits.
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And in fact, the same
has been observed in cats.
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If you stimulate the spinal cord of a cat,
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you can switch between
walk, trot and gallop.
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Or in birds, you can make a bird
switch between walking,
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at a low level of stimulation,
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and flapping its wings
at high-level stimulation.
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And this really shows that the spinal cord
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is a very sophisticated
locomotion controller.
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So we studied salamander locomotion
in more detail,
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and we had in fact access
to a very nice X-ray video machine
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from Professor Martin Fischer
in Jena University in Germany.
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And thanks to that,
you really have an amazing machine
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to record all the bone motion
in great detail.
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That's what we did.
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So we basically figured out
which bones are important for us
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and collected their motion in 3D.
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And what we did is collect
a whole database of motions,
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both on ground and in water,
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to really collect a whole database
of motor behaviors
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that a real animal can do.
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And then our job as roboticists
was to replicate that in our robot.
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So we did a whole optimization process
to find out the right structure,
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where to place the motors,
how to connect them together,
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to be able to replay
these motions as well as possible.
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And this is how Pleurobot came to life.
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So let's look at how close
it is to the real animal.
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So what you see here
is almost a direct comparison
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between the walking
of the real animal and the Pleurobot.
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You can see that we have
almost a one-to-one exact replay
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of the walking gait.
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If you go backwards and slowly,
you see it even better.
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But even better, we can do swimming.
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So for that we have a dry suit
that we put all over the robot --
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(Laughter)
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and then we can go in water
and start replaying the swimming gaits.
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And here, we were very happy,
because this is difficult to do.
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The physics of interaction are complex.
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Our robot is much bigger
than a small animal,
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so we had to do what's called
dynamic scaling of the frequencies
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to make sure we had
the same interaction physics.
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But you see at the end,
we have a very close match,
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and we were very, very happy with this.
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So let's go to the spinal cord.
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So here what we did
with Jean-Marie Cabelguen
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is model the spinal cord circuits.
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And what's interesting
is that the salamander
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has kept a very primitive circuit,
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which is very similar
to the one we find in the lamprey,
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this primitive eel-like fish,
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and it looks like during evolution,
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new neural oscillators
have been added to control the limbs,
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to do the leg locomotion.
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And we know where
these neural oscillators are
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but what we did was to make
a mathematical model
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to see how they should be coupled
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to allow this transition
between the two very different gaits.
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And we tested that on board of a robot.
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And this is how it looks.
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So what you see here
is a previous version of Pleurobot
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that's completely controlled
by our spinal cord model
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programmed on board of the robot.
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And the only thing we do
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is send to the robot
through a remote control
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the two descending signals
it normally should receive
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from the upper part of the brain.
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And what's interesting is,
by playing with these signals,
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we can completely control
speed, heading and type of gait.
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For instance,
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when we stimulate at a low level,
we have the walking gait,
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and at some point, if we stimulate a lot,
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very rapidly it switches
to the swimming gait.
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And finally, we can also
do turning very nicely
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by just stimulating more one side
of the spinal cord than the other.
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And I think it's really beautiful
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how nature has distributed control
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to really give a lot of responsibility
to the spinal cord
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so that the upper part of the brain
doesn't need to worry about every muscle.
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It just has to worry
about this high-level modulation,
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and it's really the job of the spinal cord
to coordinate all the muscles.
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So now let's go to cat locomotion
and the importance of biomechanics.
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So this is another project
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where we studied cat biomechanics,
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and we wanted to see how much
the morphology helps locomotion.
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And we found three important
criteria in the properties,
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basically, of the limbs.
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The first one is that a cat limb
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more or less looks
like a pantograph-like structure.
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So a pantograph is a mechanical structure
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which keeps the upper segment
and the lower segments always parallel.
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So a simple geometrical system
that kind of coordinates a bit
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the internal movement of the segments.
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A second property of cat limbs
is that they are very lightweight.
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Most of the muscles are in the trunk,
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which is a good idea,
because then the limbs have low inertia
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and can be moved very rapidly.
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The last final important property is this
very elastic behavior of the cat limb,
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so to handle impacts and forces.
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And this is how we designed Cheetah-Cub.
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So let's invite Cheetah-Cub onstage.
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So this is Peter Eckert,
who does his PhD on this robot,
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and as you see, it's a cute little robot.
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It looks a bit like a toy,
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but it was really used
as a scientific tool
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to investigate these properties
of the legs of the cat.
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So you see, it's very compliant,
very lightweight,
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and also very elastic,
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so you can easily press it down
and it will not break.
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It will just jump, in fact.
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And this very elastic property
is also very important.
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And you also see a bit these properties
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of these three segments
of the leg as pantograph.
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Now, what's interesting
is that this quite dynamic gait
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is obtained purely in open loop,
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meaning no sensors,
no complex feedback loops.
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And that's interesting, because it means
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that just the mechanics
already stabilized this quite rapid gait,
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and that really good mechanics
already basically simplify locomotion.
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To the extent that we can even
disturb a bit locomotion,
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as you will see in the next video,
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where we can for instance do some exercise
where we have the robot go down a step,
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and the robot will not fall over,
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which was a surprise for us.
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This is a small perturbation.
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I was expecting the robot
to immediately fall over,
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because there are no sensors,
no fast feedback loop.
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But no, just the mechanics
stabilized the gait,
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and the robot doesn't fall over.
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Obviously, if you make the step bigger,
and if you have obstacles,
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you need the full control loops
and reflexes and everything,
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but what's important here
is that just for small perturbation,
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the mechanics are right.
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And I think this is
a very important message
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from biomechanics and robotics
to neuroscience,
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saying don't underestimate to what extent
the body already helps locomotion.
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Now, how does this relate
to human locomotion?
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Clearly, human locomotion is more complex
than cat and salamander locomotion,
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but at the same time, the nervous system
of humans is very similar
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to that of other vertebrates.
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And especially the spinal cord
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is also the key controller
for locomotion in humans.
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That's why, if there's a lesion
of the spinal cord,
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this has dramatic effects.
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The person can become
paraplegic or tetraplegic.
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This is because the brain
loses this communication
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with the spinal cord.
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Especially, it loses
this descending modulation
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to initiate and modulate locomotion.
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So a big goal of neuroprosthetics
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is to be able to reactivate
that communication
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using electrical or chemical stimulations.
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And there are several teams
in the world that do exactly that,
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especially at EPFL.
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My colleagues Grégoire Courtine
and Silvestro Micera,
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with whom I collaborate.
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But to do this properly,
it's very important to understand
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how the spinal cord works,
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how it interacts with the body,
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and how the brain
communicates with the spinal cord.
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This is where the robots
and models that I've presented today
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will hopefully play a key role
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towards these very important goals.
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Thank you.
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(Applause)
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Bruno Giussani: OK, I've seen
in your lab other robots
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that do things like swim in pollution
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and measure the pollution while they swim,
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but for this one,
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you mentioned in your talk,
like a side project,
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search and rescue,
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and it does have a camera on its nose.
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Auke Ijspeert: Absolutely. So the robot --
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We have some spin-off projects
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where we would like to use the robots
to do search and rescue inspection,
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so this robot is now seeing you.
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And the big dream is to,
if you have a difficult situation
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like a collapsed building
or a building that is flooded,
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and this is very dangerous
for a rescue team or even rescue dogs,
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why not send in a robot
that can crawl around, swim, walk,
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with a camera onboard
to do inspection and identify survivors
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and possibly create
a communication link with the survivor.
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BG: Of course, assuming the survivors
don't get scared by the shape of this.
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AI: Yeah, we should probably
change the appearance quite a bit,
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because here I guess a survivor
might die of a heart attack
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just of being worried
that this would feed on you.
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But by changing the appearance
and it making it more robust,
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I'm sure we can make
a good tool out of it.
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BG: Thank you very much.
Thank you and your team.