sometimes she likes to wrap around me
like this and it's a little extracting
yeah getting her out again that's the
problem
so my area is bio-inspired robotics and
how to learn from living animals to make
robots that function as well as the
living animals because anyone can string
a bunch of servo motors together to make
a snake robot for instance but what
makes snakes so special is how they
actually control their locomotion it's
those control algorithms that we're
trying to figure out that gives them the
versatility they need to move through
their habitat
we start by analyzing how they move so
we use motion capture cameras and study
their motion we use instruments to study
the forces we're currently embarking on
a project to understand their muscles
but also a key aspect is going to be
understanding what happens when they
encounter a disturbance if they're
moving through a series of of objects
and one of them yields and breaks how
does the snake respond to that
disturbance that gives us insight into
what they're controlling are they
controlling force velocity position
how are they handling this we have a
robot that's capable of three of the
four modes of snake locomotion
we're very limited motors are nowhere
near as good as muscle yet in a variety
of ways uh
we can't our snake robot for instance
has uh 24 servo motors whereas a real
snake she has over 200 vertebrae in her
body and several dozen more in her tail
each of which has 40 different muscles
crossing every single joint yeah we're
still a ways away from replicating the
true elegance of snake locomotion
so yeah you're obviously well known for
the uh having the snake yeah
the snake is arguably the most famous
part of the lab
and i'm finally i'm i'm working on a
grant for him but
she's poking through the sideburns
[Laughter]
oh radiance
move this and this
i really need to pay them to put more
power outlets in this place
so what's your lab then is if you say
it's um
biology inspired robotics yeah by
biology comparative biomechanics
bio-robotics because it goes both ways
we can use the animals to help us
understand how to build better robots
but the great thing about robots is
unlike animals robots will do what you
tell them to do every single time and
they'll do the same thing every single
time so it makes it easy to test
hypotheses including sort of
what if hypotheses what if the animal
didn't do the thing that it does to
adjust to a particular environmental
change or what happens would it fail we
don't know because the animal won't do
it but the robot will so because we tell
it to
the robot is actually quite simple it's
just a series of
dynamics servo motors dynamics xl320s so
these are commercially available servos
and dynamic soles they have their own
controller but it's basically a modified
arduino arduino-based code so on and so
forth
so
bring this around
and
it doesn't even it's not even that good
of an arduino it's not like a mega or
anything
there we go oh i need to fiddle with
those parameters so yeah
so
this one the snake robot is performing
uh sidewinding let's give it a little
boost for speed sidewinding is this
strange mode of locomotion used by a
variety of desert snakes
and it can use sidewinding to move on
shifting desert sands does sand is very
hard to move on for a variety of reasons
but the short version is you press it
one way it solidifies like a solid if
you press it another way it yields and
flows like a fluid and predicting which
is going to happen is very difficult and
so snakes have evolved this method that
allows them to move across a huge range
of sand substrates very easily and
it's robust to the different types of
sand they don't have to test for exactly
what the sand is doing
so i did some previous work at georgia
tech with the actual sidewinder
rattlesnakes and that's how we came up
with the algorithm for this which is
really just two sine waves they have a
vertical horizontal wave right to left
along the body and a vertical wave you
can see how it's lifted its body clear
of the substrate here so it's got this
lifting and lowering sort of system
going on
as a result it can transition to lateral
undulation and then back to sidewinding
but basically we have a sine wave for
left to right a sine wave for up and
down and they're slightly offset and
that's it the actual code to produce
this is maybe
15 lines and so similarly for lateral
undulation
let me fiddle with the parameters for
that one before it swaps over so snakes
can move through this typical slithering
gate and this is still a pale imitation
of the grace and beauty of real snakes
but
this is just a single wave we're working
on more complex implementations and
finally it can even perform something
called concertina locomotion
and so once it gets to that point
it'll finish a cycle so this is what
they do inside of a tunnel if it hit the
tunnel wall it would be detecting that
unfortunately i don't have the tunnel
set up at the moment but basically it
stretches its body forwards like you see
here
and then it feels for the wall of the
tunnel and if there was a real tunnel it
would detect that
and automatically adjust itself and then
inch worm its way forward just like the
real snake it's actually not a terribly
efficient form of locomotion and that's
true for these guys as well their
endurance drops dramatically when you do
this it's sort of a last resort mode of
locomotion so the only one it's missing
so far is actually a form called
rectilinear and that's actually where
they can ripple their belly scales alone
it's a form of locomotion powered
entirely by the skin and unfortunately
we don't have skin actuators that are
good enough for that yet but we're
working on it so
can you say right go over there and that
sort of thing this is a purely
feed-forward mechanism so it does not
yet have external sensors that's another
area that we're working on
how to control this thing so right now
the biggest issue is they're still
tethered because they wind up drawing a
tremendous amount of energy
when they i mean this thing is pulling
over an amp at any given time so it
sucks down the energy pretty fast it's
yeah we're a ways away from fully
autonomous snake bots but we're getting
there bit by bit i like to say that
snake robots are sort of where humanoid
robots were 20 years ago and now look at
boston dynamics and in fact boston
dynamics is an excellent example of this
all of those magnificent robots they're
based on the uh the control mechanisms
observed for human locomotion so when we
walk we use an inverted pendulum we sort
of vault over a stiff limb and when we
run our limb becomes springy and by
controlling those dynamics that's how
boston dynamics is able to make their
robots do amazing things is because
they're trying to control just the
center of mass trajectory and the
springiness of the effective limb which
can be multiple limbs if it's one of
their quadrupeds
and then they have sort of secondary
processes i imagine that they
handle all the little sort of details of
what joint gets how many volts and
things like that just like with us
it's all handled in our spinal cord
there's a lot of that stuff where we're
walking our brain is just sending a few
signals saying go roughly this fast in
this direction and the spinal cord takes
care of all of that stuff of which
muscle turns on when and how and
responses to a perturbation like missing
a step or something like that so there's
a lot of decentralization even in humans
so is this something anyone could do
absolutely this is just off the shelf
servo motors xl320s with 3d printed
brackets connecting them but i've built
tons of others with regular high-tech
servos and then you just uh impose a
sine wave what i basically do is i i say
here's a i compute a sine wave and i say
every motor has a certain phase offset
and then i impose a global phase offset
on the sine wave at successive time
intervals and the trick is i sort of
tweak the time interval so that the
motors have enough time to get where
they're going
the other thing is dynamic soles are
great because you can daisy chain them
so if i
pop this out so it's not no longer doing
anything so i can string
one input along for six motors so this
is the
vertical lead the horizontal lead for
these six you can technically go more
than six but i wind up having problems
with the voltage
drops at the end and the motors aren't
quite doing what they need to you could
see that a little bit at the tail
sometimes the voltage drops a little bit
at the tail
normal servo motors it's just a simple
one one thing you can hook them up in
parallel with a lot of soldering if you
want but uh my personal favorite for
snake robots that aren't dynamic souls
is actually the linx motion controller
links like the animal and it has 32
servo channels i use python because it's
a snake name and i like snakes but also
it's what
my predecessor used and so
you just send a serial command that says
channel number 13
go to position
750 and take
700 milliseconds to do it and then you
just repeat that send all the commands
in a chain and the robot will go to that
position and then you wait for a little
bit go to the next time step move it to
the next position so on and so forth
these are more sophisticated than
regular servos for all sorts of reasons
but yeah the ultimate end game for this
is snakes the whole reason snakes
evolved the whole reason they lost their
limbs and got this elongate body form is
to move through cluttered complex and
confined environments so they're really
good at dealing with those sort of
things like say exploring mars or a
building has collapsed and you want to
find out if there's people under there
or you want to go sneak into a bad guy's
house and see what they're talking about
through the walls and the cabling and
things like that that's what snakes are
excellent at and that's why this
elongate limbless form of body has
actually evolved
over 24 independent times just in
lizards snakes are merely the most
successful of those there's actually 23
other groups of limbless lizards
plus a bunch of other times so it's a
very very common strategy and it's
always associated with these cluttered
confined environments which is where
limbed robots and things with more sort
of chunky boxy bodies don't do as well
in fact if you or a dog or an insect
runs across a cluttered field of rocks
and logs and debris in order to not fall
down we get slower we have to slow
ourselves down to accommodate this
complexity snakes actually get faster
because when they're doing that
undulating form of locomotion what
they're doing their body is hitting
those obstacles and using them as push
points so they get faster the more
cluttered their environment is and so
that's a real advantage and something
that people are keen on capitalizing on
so
we've got this motion capture system
and we're going to be looking at the
arboreal locomotion of snakes and so the
idea is that we'll take a snake and
we'll put little reflective markers
message maybe you're sending a video
suddenly the bandwidth becomes actually
a bit of a problem this may not be an
issue depending on the application