My spiel is that if you look at limbed motor control,
if you measure our level of understanding by what we can
make a robot do, then walking is by far a harder task and less
understood than reaching units.
So in that sense, it's very interesting.
So there's a trend, especially at MIT
here, to try to make the robots a little bit more like biology.
You'll see this today because each of the motors on Troody
actually has a spring attached.
Right, so that's the first step in kind of taking--
I'll show you maybe some rigid robots later.
But if I'm going to a very rigid type of robot
to one that's more fluid, maybe a little bit more
like what biology's doing.
And that brings up a lot of challenging control questions.
And I think that Troody is an excellent example
of a bipedal robot that actually works despite the fact
it has springs.
Right.
So this is a proof of concept and hopefully the spring idea
will lead to some very exciting and floppy robots
in the future.
So Pete, take it away.
All right.
So everybody, I want to begin by--
I was talking a little bit earlier with Russ about a way
to explain the whole idea of using springs
that could motivate this a little bit better,
maybe for all of you.
And there's just three main reasons
why I think springs are really a good way
to go with this particular type of technology.
And before I go on, I should certainly
give credit where credit's due.
The originator of the idea of using springs in series
with a motor, which is called a series elastic actuator,
was done by Professor Gill Pratt,
or he's previously a professor, he's now at Olin College.
He's one of the people who's starting up
Olin College, which is a pretty interesting story, [INAUDIBLE]..
So Gill kind of just came up with the idea
of putting a spring in series with a motor
and taking advantage of the properties
of the spring and that whole control movement.
He has kind of a electrical engineering background
and he thought of it in those terms, the springs [INAUDIBLE]
capacitor or whatever.
The basic idea is that you have a position controlled
robot, which I'm certain you're all familiar with.
You have a motor connected directly either to the joint
or to a small transmission gear reduction to the joint.
And if you grab the end of the robot
when the motor's turned off and move it,
you'll find that the motor will spin,
and you'll back drive the motor or if the gear ratio is very
high, nothing will happen because you can't back
drive the motor.
You might even break the gears if you move it.
That's sort of the way the position control joint feels.
The way this joint feels is entirely different.
If you turn it off and move the joint,
the spring that you have in series with the motor
will stretch if you wiggle the joint.
So if you were to grab the motor and keep it from spinning,
you could move the joint a fair distance
because the spring is taking up a lot of the locomotion.
And as you push it, you put energy to it.
If you let it go, it'll bounce back to its zero set point
and you can pull it back the other way.
So it feels different, sort of feels fundamentally different.
And again, if you let go of the motor,
you could back drive the motor, but with a spring, kind
of in there.
And so it's everybody--
can never be imagined.
OK.
So now the three main points, the three main reasons why
this is good are one, because the spring takes up
shock, meaning that if you take the position-- remember how
I said if you take the position controlled system
and if the gear ratio was high enough and you move it,
you try to move it, nothing will happen.
It feels very, very stuck.
Well, if you shock the end of a robot arm,
if you hit it against the wall or if you're
walking, if your foot lands on the ground,
if that gear ratio is extremely high,
or just if you have gears in series with the motor, OK,
every time you hit the ground, you're
going to be putting these large loads on the gear train.
Sort of a very instantaneous spike.
And over time, that will break your transmission.
OK.
And it may well break it right away
or it may break it after a few months.
But the point is that that's a very damaging thing
to do to a mechanical system.
So what the spring does is it acts
like a shock absorber in a car.
When you hit the ground, that initial huge spike
is taken up by the spring, just like a capacitor takes up
a voltage spike.
So from a purely engineering perspective,
you get an instant benefit in terms of mechanical robustness.
OK.
That's the first thing.
The second thing is--
let me see if I remember this--
that the spring gives you a way to invert
the dynamics of the robot.
And so this is a little bit of subtlety here, not much,
but the basic idea is if you have a position controlled
system, if you move the arm to a certain angle,
you typically have a feedback loop, a PD loop.
OK.
So you have a proportional gain and a derivative gain.
Now, if you move that to a certain position
and it's staying at that position, and you grab it,
this is in the case of a position--
this is in the case of a position controlled robot.
If you grab that arm and move it, [INAUDIBLE] move it
a little bit because you're going
to be introducing an error into that feedback loop, right?
OK.
So in order to reduce the amount of that error,
you have to turn up the gain on that controller, right?
And naturally, if you turn that gain up high enough,
it'll go unstable.
OK.
So your goal in life as an engineer
is to keep that gain as low as possible
because you want the robot to be stable,
but then make it as high as possible
so that the robot does exactly the right thing.
So there's always this tension, you're
fighting between instability and the performance of the system.
The spring gives you a really clever way
to tackle that problem.
If you look at position controlled robots that walk,
OK, and I'm really dealing specifically
with the domain of walking robots.
One of the problems you have is that the robot has
a fair amount of mass to it, you have
to have all the motors, the batteries, the computers,
you wind up with--
a tree weighs 10 pounds so it's holding up--
the body itself weighs five or six pounds,
it has to hold up that weight.
Now, if it was a position control robot--
and there are several position control robots out there--
quadrupeds, [INAUDIBLE],, the Honda robot.
The position controllers need to have relatively high gains
in order to function well.
Right?
Because there's all this mass that the joint's
trying to hold up.
So in order to keep the mass in the right place
so that you can keep the dynamics right,
all the mass and torque's in the right place, that [INAUDIBLE]
these very high gains.
And the only way to keep such a system
stable in a purely position controlled domain
is to have an extremely high performance actuator.
So you need very, very good motors
with very high gear train that's very well made.
There's no backlash.
Your components tend to wind up being somewhat expensive.
And not only that, but if over time they wear
and you get some play in the system or the gears start
rattling, that can introduce some serious problems
because all those things will naturally introduce instability
into the position control loop in which you just
set very high gains.
OK.
Now what the spring lets you do is
invert the dynamics of the robot, which what I said
I nee--
you're taking into account the mass
of the robot in a separate controller
from the one that actually performs the walking motion.
So in a position control robot, you have one batch of software
that says, make the robot stand like this
or move the leg like this to walk.
In the force control [INAUDIBLE],,
which is Troody, or any of the robots in the LegLab,
you have two parallel software modules.
One software module says, just apply forces
to counteract the masses of the robot.
So in other words, make the robot
feel as though it is floating in space, that there's no gravity.
So that's sort of the inverting the dynamics part.
And running in parallel with that,
you have another control loop, which
says, move the leg this far, move it forward that far,
that kind of thing to do that actual walking.
And the cool thing about that is that the major force that's
applied to the robot--
if you look at the amount of a force being commanded
to the joint, the software routine
that takes care of the gravity of the masses has a large turn.
Its turn's relatively large, and the one
that's controlling the positions of the joints
and making the robot walk has a relatively small addition
to that.
OK.
And that's very important because the gain
on the one that inverts the mass is a very low gain.
You can make that gain extremely low because your joint angles
can be off by large amounts and the system
will still perform very well.
And the gain on the other one can be very low
because you've already taken care of most of the forces
with the conversion of the inverse dynamics.
So what you wind up with is a system
that can perform relatively well and do
the right thing but that winds up being stable
with the gains in the right place.
So that's the second thing.
And the third thing is that the--
[INAUDIBLE]
The third thing is that when the robot is walking, what you'd
like to do is typically have the motion be very quick and fluid.
So if I'm walking kind of like a robot--
kind of go slowly like this, I'll
slowly move my foot up and move it forward, slowly put it down.
And I kind of have to move slowly
because in a position controlled robot,
if you move very quickly, you're liable to just smack
the foot down on the ground and introduce this huge disturbance
into the robot and it might keel over or something, very simple.
But with a force control robot, when the foot's in the air,
you can command a force, a very small force
to push the foot down.
And since it's in the air, it'll go down
very quickly because there's nothing pushing against it.
OK.
So a very small force command can cause
a rapid motion of the leg.
But once the foot hits the ground,
it hits it softly because it's being
commanded with a low force.
And so the basic idea is that in a position control system,
it's sort of an oxymoron to say, hit something quickly
but softly.
Like, this is not a concept that makes any sense.
But with a force controlled robot, you can do that.
You can say, hit something quickly but then when you hit
it, give it a soft touch.
And that allows you--
You said depending on a low mass--
Yes, if the leg was extremely heavy--
it's not a perfect thing.
OK.
But by keeping the legs lightweight
and keeping the bandwidth up, you can kind of achieve that.
Yep.
And so that last point is a critical one
because it allows the robot to have
a fluid and rapid smooth motion to it, which is necessary
in order to kind of have biological realness to it.
So those are the three main reasons
kind of why I like how the springs and series would
work, so.
So let me say one thing that maybe--
to tie it in.
In robotic technology, things were always
very precise movements.
Right.
So position control made a lot of sense in that case.
Robotic arms, you want high precision.
And walking, it seems like high precision is not the way to go.
So what Pete's saying is instead of having very stiff, very
accurate motors, we're putting springs in, right,
and it changes the way we have to think about it.
It's more like a muscle activation or some--
loosely, it's more like a muscle activation
than a particular servo command.
And it allows you to kind of--
when I'm pushing against things, it's more of a force command
than just say, go to this position and stop.
Right.
So it's a different way to think about things.
Yeah.
I mean, they're kind of duals of each other, you could say.
Because in position control, you're
more concerned with getting the angle just right.
But you don't really know or care what the force is.
In force control, you don't really
need to know exactly what the angle is, you don't really
care exactly what it is.
But the force is important.
You can say, hit it hard, hit it soft, that kind of thing.
So there's that side to Troody.
Another side of Troody, of course,
is the walking on a limb itself.
And for that, it uses a controller,
which I call the PQ controller.
So essentially, what the robot does
is it has inside of its body a dual axis accelerometer
and a dual axis rate gyro.
And it takes those four pieces of information
and does some processing on and it generates a vertical--
it's software vertical gyro, so it
knows which way gravity's pointing, which way up is.
It also knows its linear velocity,
it's X and Y velocity, which of course, as Einstein observed,
is relative.
So it only gets to linear velocity
for sort of a short time period, but it's
short enough for the robot to make use of it.
It's like a person.
Like, if you get on a train, right, and close your eyes,
you can feel the train speeding up,
but once it reaches steady velocity,
you no longer sense that you're moving at a certain velocity.
So the robot has the same exact thing.
In other words, Troody can get diz--
It was Galileo, not Einstein.
Pardon?
It was Galileo he's quoting.
It's not Einstein.
I'm sorry, I'm sorry.
[LAUGHTER]
[INTERPOSING VOICES]
So--
Translate this.
He said it's Galileo, not Einstein.
Oh, Galileo would say that.
He's Italian.
Oh, my apologies.
So anyway, the--
Sorry.
So it's OK.
So the robot has X and Y velocity.
And X being front, back, and Y being side to side.
So it has XY velocity.
And then it has XY rate of roll, XY acceleration, and then
absolute roll and pitch.
So it has a lot of different bits
of kind of vestibular information inside of it.
And the velocity term, actually, turns out
to be one of the most important ones.
The X and Y velocity is--
once I got that working, that was
kind of the last major hurdle to getting the robot
to walk stably because by having those velocities,
you can use them as a damper, as a damping turn,
to control what the mass of the robot is doing.
It turns out that dampers and hardware
are much more difficult than they
are in the world of simulation or theory.
The problem is because the way you generate a velocity
turn, typically is you make a success of subtraction
of the value of the sensor.
And if you ever have any noise or spikes on that,
you're going to get all kinds of amazing noise
and your velocity gets squared or cubed or something.
So when you take that differentiation,
you amplify your noise.
So there's always a constant battle
among people who do robotics to get
smooth reliable damping turns so that their joints give
this really weird humming and vibration.
So I had that problem with Troody
when I was using purely mechanical joint angles
and things like that for damping.
But once I got the damping from the gyroscope,
the gyroscope is a separate system
from the mechanical system of the robot.
It's a solid state device so it's relatively smooth.
And the other nice thing is that I'm
integrating to get velocity.
I have an accelerometer and I'm integrating it.
So therefore, I'm actually reducing the noise.
And so I have this incredibly smooth velocity signal now.
And that means I can crank up a lot of gains
on other parts of the robot and use that as my damping turns
to stabilize the robot.
So that's a very important part of it.
Troody has all of its masses in joint angles.
So every sensor has--
every joint, rather, there's 16 joints
and every joint has a force sensor and a position sensor.
So the robot has a kinematic model of itself inside.
It has all this mass as--
it knows the mass of each link and kind
of roughly where the center of mass is of each one.
So it computes from that various things,
like center of mass, center of pressure.
Could you just point out all the joints?
Yep.
Sure, I can do that if you don't mind.
So the joints are a tail, which goes up and down
and side to side.
And just two of these springs here that
serve as the force sensor.
The legs can go in and out and they can twist a little bit--
Like that.
And the main motors, these are little Futaba airplane
servos that I just kind of cut away the electronics
and just using them as gearhead motors
because they're very nice, the gearheads
are very smooth and everything and they're cheap, so.
So you took out the servo?
So I took out the servo.
All right.
Thanks.
Because you have your own servo?
Own servo [INAUDIBLE].
And so the main power, there's three big motors here.
So this is pitch for the hip, this is the knee,
this is ankle.
And so there's a redundant degree of freedom in the leg,
in this case.
And the foot is two feet-- one, you have pitch and roll.
[INAUDIBLE]--
And there's sensors, force sensors, springs.
Every joint has a spring.
So this cable drive for the main leg joints with compression
springs and the other joints use sort
of beam springs with a little potentiometer
hooked up next to the spring [INAUDIBLE]..
So is the [INAUDIBLE] actuated?
Yes.
There's two motors--
What kind of motor are you using there?
These, for the feet?
Yeah.
They're the same, Futabas.
They're all Futabas?
Do you want to know the kind?
It's like, S--
No, just curious.
And then they're, like, cordless motors.
There--
Hobbyist motors.
Yeah.
They're not all like the RC cars, remote control cars.
They are, actually.
Remote control planes.
They have those too.
I know all the--
The big ones.
The big ones are Pittman--
standard Pittman.
They're all PC brush motors.
Pretty ordinary.
But [INAUDIBLE] of the robotics use, they know cheap,
off-the-shelf components.
And so like these Pittman's are $40 bucks a pop.
So how much did the whole thing cost to make?
If I had to make a new one and I can make a new one,
I can do this for probably $4,000.
Wow.
So.
And what's the major-- so the motors
are about what, a hundred, two hundred each, or?
Yeah.
Call it like, a hundred or two each.
Yeah.
And I mean the computer's going to be about $1,000 bucks.
Data acquisition, $1,000.
But that's still very cheap for a robot
that does what this does.
The Honda robot is--
$350 grand.
Yeah, something like that.
Yeah.
And--
So what about the computer?
And the spring.
The computer is not very interesting.
It's a TIC32.
It's an old computer.
For this day, it's very slow and awful.
But it's [INAUDIBLE].
So is it all that on board?
Yeah, everything is on board.
So we don't have any power?
So yeah, it has batteries.
And I've run the robot off batteries.
The batteries right now are damaged.
They won't work, for some reason.
But typically, when I was working on Troody,
the way I would use it is I would have a serial cable,
there's an for a serial cable that would go to a PC
and I'd write what the [INAUDIBLE],, compile it,
download it to the robot, and it's a flash [INAUDIBLE]..
And then you can--
So when's your initial [INAUDIBLE]??
An IPO?
Well, I--
Sure enough [INAUDIBLE].
[INAUDIBLE],, on that topic, I mean,
right now, Troody's retired.
And I'm going to [INAUDIBLE] until it just gives up
the ghost, I guess.
I mean, I might try to maintain it a little bit.
But I goofed on building a quadruped and a biped,
which are going to be covered in a covering
to make them look like real dinosaurs.
And the goal is to start a business that sells
walking dinosaur robots, so.
All different kinds of robots.
Not going to be 40 feet tall?
Well, we'd like to build big ones and small ones.
I see.
Yeah.
So we'll see what happens, but I'm
right in the beginning stages of that, so.
But this one currently lives in a museum.
This one lives in the Museum of Science in an acrylic case.
I give a demo at the museum about once every month.
And they have had a robotics exhibit there for a while
and that exhibit is shutting down.
But they've asked me to give them Troody,
so Troody might become a permanent part
of the collection of the Museum of Science,
which would be cool.
I used to go there when I was a kid.
So I can try and give you a demo.
Do it.
I can't make any promises.
The robot worked yesterday but it didn't work the day before,
so.
So you just got to hope, and--
If it's going to take a couple minutes to warm up, I mean--
It's going to take a couple minutes to warm up, yeah.
So maybe some videos or something
to keep people [INAUDIBLE].
So figure out [INAUDIBLE].
So I just brought up a couple of videos
that can help you put things in perspective.
LegLab springy robots versus Honda-style mission control
robots that'll help you understand
what Pete's been talking about.
Can I ask one thing about the design, with the motor off,
I mean, it's amazingly much closer
to any biological system than a truly position
control [INAUDIBLE].
But if you think of a biological leg or eye,
can see that the more compliant [INAUDIBLE] actuating the mass
it'll stay straight but have a relaxed program brought in, is
even--
It's even more compliant.
Yes.
Right, right.
And in a sense, we know all right,
that there's a lot of national dynamics
to get the support [INAUDIBLE].
Like, [INAUDIBLE].
So this doesn't look much like [INAUDIBLE]..
Right.
I mean, this is kind of [INAUDIBLE]----
Is there any specific [INAUDIBLE]----
This is a pathway between a truly biological system
and a purely kind of [INAUDIBLE]----
Isn't there [INAUDIBLE] development
in doing actually quite a lot of passing dynamics?
Yes, absolutely.
I mean, the springs in these robots
can already function as [INAUDIBLE]
so we can always take advantage of that.
In order to do that really well, [INAUDIBLE] to the springs--
Right.
[INAUDIBLE]
And then the optimal thing, I mean,
one of the main drawbacks of this
is that this the spring's like a fixed spring constant,
and of course in the muscles, we can change that.
So if there was some way to vary that,
that could potentially add a lot of [INAUDIBLE]..
We'd have to add a whole new kind of [INAUDIBLE]
to change that.
One thing that I would love to do some day
is find someone who's built like an artificial muscle.
They had another case based on a--
Right.
There's some [INAUDIBLE] trying to do that, yeah.
If they can give me, like, [INAUDIBLE]----
Just the science.
Just, like, plug it in and it works, that would be great.
I mean, I'd love to do that because that would be almost
identical to the biological.
And I think we already have the control systems now
to handle that, so.
Another thing that this can do, you
can actually tell the motor to observe zero [INAUDIBLE]..
Right.
So that's something you can [INAUDIBLE] for.
So some of the--
Yeah, yeah.
You can make it--
It can simulate.
It can simulate, right.
[INAUDIBLE]
Yeah, yeah.
And actually, Jerry Pratt wrote a thesis
called, exploiting natural dynamics in bipedal walking,
which [INAUDIBLE].
I won't take much away from you, but you
can see this guy swings his leg forward passively, actually.
So this is another one of the LegLand robots.
And as soon as the leg gets about halfway
through the swing phase, it just turns off.
It exerts zero torques and swings forward.
Is this person having to simulate the controllers?
If you turn off--
Yes.
--the motor, is it stiff like this?
That's right.
OK.
So.
So might as well give it a shot.
All right.
[INAUDIBLE]
So now that-- so there's no--
are you controlling or is it just he has to--
This is a joy stick on top.
OK.
And a kill switch.
It's one of the safety aspects.
Kill switch.
[INAUDIBLE]
This side's about ready to begin.
Transmitting.
So there's just a slight--
funny that foot's still [INAUDIBLE]..
Yeah, Troody's once again a little [INAUDIBLE]..
Let me just let it warm up for another minute or two.
Maybe it needs to warm up.
[INTERPOSING VOICES]
That's what I'm here for.
Yeah.
Just gyroscope's kind of warming up a little bit
and there's some component on one
of the feet I think it's starting to fail
and maybe a thermal [INAUDIBLE],, but I'm not sure, so.
Yeah.
What results do you have?
Pardon?
What kind of diagnostic do you have to [INAUDIBLE]..
Oh, well, just--
You can look at the raw sensors?
Yeah, you can look at the raw data from the sensors.
You don't have anything like, more [INAUDIBLE]..
I mean, all you--
Your brain is the diagnostics.
My brain is the diagnostics, yeah.
Exactly.
So we'll give this another whirl.
Come on, Troody.
[INAUDIBLE]
So now it's immediately on the--
There it is.
A couple of [INAUDIBLE] steps.
[APPLAUSE]
See if you can make the table [INAUDIBLE]..
Well, Troody, Troody when it's working,
it's pretty good, actually.
That's another advantage to force
control, since you don't care what the joint angles are,
doesn't matter what the terrain is doing.
The terrain can go up and down and the foot,
once it hits that terrain, it'll just kind of
sense an issue, so.
And I might as well just show you another trick, just
[INAUDIBLE].
[LAUGHTER]
Apparently, [INAUDIBLE].
You're going to try to get a reaction?
We'll try it this way.
There.
Cool.
[APPLAUSE]
I can't do that sometimes.
We got a demo on the robot so I'm
going to go turn it off now and not push my luck.
This robot was completed about a year and a half ago.
I've kind of left the lab and I'm now
in the process of kind of finding all the software
because I want to have the ability to maintain it and kind
of keep demoable.
So I'm kind of refiguring out how to do that, so.
Typically, there's two ways that it fails.
The first way it fails is if something breaks.
And you have to kind of track down which joint is broken
and you diagnose that.
So in this case, there's something wrong with the foot
and I need to find out where it is.
More commonly, one of the springs will stretch
or something and you'll lose calibration.
So the robot needs to know kind of when it's at rest,
it needs to know what zero is, the zero force.
So the good way-- way to to this, you'll hang up the robot,
read all the joint sensors with the motors turned off,
and then put those numbers in for zero
to help calibrate the robot, and that's something
that you'll be doing once every few weeks
with the typical robot, I think.
Because parts kind of stretch and change over time.
But once you have that zero point, the scaling from that
is usually pretty consistent.
You don't have to worry about that.
Again, because the force control doesn't
require very exact values.
So if the scales are off by a little bit from spring
to spring or whatever, it doesn't affect
the stability of the robot.
And if this thing was sitting in a glass case for a year
and a half, and you took it out last week and it got
[INAUDIBLE],, right, and that's sort of--
That's impressive.
It still works.
Yeah.
Awesome.
What is the power emission?
What's the what?
How much power does it require?
How many parts?
No, power.
Power.
Oh, how much power?
Oh well, the supply needle--
I haven't really measured exactly,
but I mean, just going by the supply,
I think it uses somewhere around 75 to 100 watts.
Something like that.
And I would say the vast majority of that
is actually wasted in heat.
Because the [INAUDIBLE] parts and the electronics
get very hot.
In fact, I'm working on some new electronics.
The actual walking itself probably
takes like 15 watts or something.
Wait, so humans about 100 watts also?
[INAUDIBLE]
Yeah, I don't even know what it is.
If it [INAUDIBLE].
Troody hardware is--
--comparison.
Troody's electronics is very, very different--
Different technology.
Yeah.
[INAUDIBLE]
So.
The motors themselves are pretty efficient,
like an electric motor can [INAUDIBLE]
in the 80% efficiency rating.
Geartrain, same thing.
So most of the loss is just the electronics.
Any other--
Man.
It's very, very beautiful.
Think it is special whether you want
to do become more sort of investment product
or something?
Well, yeah, I--
So maybe even there could be more things to get inspiration
from biology.
Like this issue of sensors, if you have to have redundancy.
Yeah, I'd love to have redundancy.
So maybe having much, much less accurate sensors
but maybe more of the--
Yeah, if there was a way to package that.
Right.
But then it could be different technologies--
Right.
Yeah.
But instead of having precise force measurement,
having a hundred fibers that'd give you a rough measurement
and different--
[INTERPOSING VOICES]
And then you do some [INAUDIBLE]----
Right, right.
That would be perfect.
Yeah, because one of the problems is potentiometers
will fail and then you're toast, so.
Yes.
Plus, you can have some sort of built in diagnostics and pain
receptor.
Yeah.
Yeah, yeah, yeah.
Something that tells you that the sensors on [INAUDIBLE]..
Right, I mean like it's--
[INTERPOSING VOICES]
Especially if you start having 1,000 channels because you
have sort of distributed sort of information gathering.
You want to have some sparse information about it all.
Right, right.
Well, there's a lot of issues.
I mean, if you have hundreds or thousands of sensors,
then you need to have data acquisition for all those,
which I mean, I could barely cram like,
32 analog channels in Troody.
Right.
So I mean a lot of technology I think
needs to change before we can really do
what we all kind of dream of.
So Troody's kind of a hack in a way,
it's kind of using old technology
to try to solve these problems.
And you know, we need fuel cells,
we need just many forces of magnitude,
more inputs for data.
Like I said, redundant sensors.
We need muscle actuators.
We need all these new technologies
that just don't exist yet.
In terms of not existing, in terms the parallel processing
chips [INAUDIBLE] different sort of thing, are there any--
obviously, parallel processing is
how we do it, are there any parallel chips that
can be adapted to a multisensor processor, or are they done?
I don't know.
I mean--
They should advance the [INAUDIBLE]
there because the frequency of the computational rate
and the processor is completely [INAUDIBLE]
faster times [INAUDIBLE] so you simulate [INAUDIBLE],, right.
So if you go with any [INAUDIBLE] plus the speed,
you need the fuel one hundred cycles for [INAUDIBLE]..
The problem is effective cycles, you
can have thousands of parallel [INAUDIBLE]..
Right.
Well, I guess-- sorry, maybe I guess
that the computation that you didn't have,
I was just wondering why.
On that onboard unit there, that seemed to be a limitation
but the computational power doesn't
seem to be a problem handling multiple sensors.
The computer in Troody is loaded.
I mean, like I literally couldn't put any more
computation on the robot.
I'd have to slow down its control loop.
Right.
So you'd need another chip of a series, right,
or there's nothing wrong with putting a parallel machine.
[INTERPOSING VOICES]
--relatively all the [INAUDIBLE] processing, it's old.
I mean, for the new robots, somebody
buying a PC/104 Pentium III or whatever,
I'll have more than enough horsepower
for the type of programming I'm doing.
But you know, I mean, one thing that I
would love to have someone work on is some kind of a learning
and adaptive system.
And for that--
Russ was talking about that.
I mean, that's actually not my field.
And one problem with the robot is
that I do all of its learning and its adaption
and once I'm done, it can never get any better.
So I would really like the robot to be
able to work for months and months
and slowly get better and better.
I mean, that would be great, so.
[INTERPOSING VOICES]
I mean, just as much as all the other things I mentioned,
that's another critical technology, which is needed.
And fortunately, that's one which
we can do because we don't have to make anything.
It's purely conceptual.
And another aspect of the learning
is that each robot will be the same as when it's first
manufactured but they'll all kind of, over time,
tend to diverge because different robots will wear out
in different ways.
They'll be in different environments.
So again, having an adaptive system
enables each robot to adapt to its own particular foibles
and optimize itself.
So that is an extremely critical area.
And for a large neural network, perhaps, you
need some kind of custom--
a parallel processor or something like that.
I came in late but did you-- the control that you're using,
are you using a regular kind of state machine?
| mean it's a event cycle loop.
I think it runs at like 500 hertz.
It's a state machine, and I have a controller
in there, which looks at the ZMP and kind of does
some funky geometry on the ZMP.
ZMP is how it works?
The zero moment point.
So essentially, the robot knows the point
on the ground at which it's angle of momentum is zero.
Above [INAUDIBLE]?
Center of pressure.
So physically, it's center of mass plus the velocity.
So think of it that way.
So it's a very simply control system.
It's a simple linear, kind of hacked together control system.
And it seems to work pretty well.
We actually got Troody on a forced plate
last week over at Spaulding Rehab
and the center of pressure--
we put little golf balls on it, the little reflective golf
balls--
took like an hour.
We graphed the center of mass of the robot
and it looked very biological.
This little sort of side wave, right, and it
never went all the way over to either side, to either foot.
So Troody's definitely trying to be dynamic
in the way it's walking, so.
Which is kind of good.
Just very fast--
It's a very simple control system.
But the controller is implementing a virtual control,
which is this-- right?
Virtual controller?
Right, like [INAUDIBLE]--
Sure.
Yeah, it's a virtual controller.
Yeah.
So this control loop is actually transforming like this mass,
like it's moving, while the other controller keeps it
[INAUDIBLE].
Exactly, exactly, yeah.
So the high level controller, it's
a abstract cell kind of all the joints
of the leg, that kind of thing.
Right, right, right.
Exactly.
Yeah.
Have you tried giving it some kind of extra perturbation
like--
Well, yeah.
We--
What direction is that--
Somewhere at the lab we have some video,
we put it on a board and kind of did this with a board,
and we actually were able to move it pretty fast,
and the robot could just stand there.
So it's very good at balancing, kind of.
It could stand on a boat, basically.
How about an escalator kind of where the surface ground itself
is moving?
Moving sideways?
I haven't tried that, actually.
I mean, I don't know what would happen.
I suspect that what you saw moving that the damper would
tell the robot to lean over but I'm not sure
how that would stabilize it.
I mean, it's a relatively simple robot.
I mean, you saw it balancing on one leg.
So I wouldn't be surprised if it sort of
tried to do the right thing, whatever that is.
But I haven't pushed the robot too far because it's
a very delicate machine.
One experiment I did do was I made it walk across a desk
and then I put a notebook, which was about a half an inch
high, in front of it, and the robot had, of course,
has no vision and no concept of where it is,
but it was able to just stumble over the notebook.
And it stumbled, it began to kind of walk funny
but it made it over the notebook twice and didn't fall over, so.
So again, that's one of the beauty of springiness
and the floppiness of the robot is
that it can withstand sudden changes in ground level
and things like that.
But the most I've done in terms of perturbing the robot is
making it [INAUDIBLE],, center it on a tilted thing,
the notebook.
And one day we had it sitting outside
and there was a pretty brisk wind, actually, like a 15,
20 mile an hour wind gusts, and it seemed to take that, so.
Cool.
Yeah, so.
We should be [INAUDIBLE],, if you have
anymore questions [INAUDIBLE]?