This tiny robot weighs less than a tennis ball
and can jump higher than anything in the world.
In the competitive world of jumping robots,
the previous record was 3.7 meters,
enough to leap a single-story building.
This jumper can reach 31 meters,
higher than a 10-story building.
It could jump all the way from
the Statue of Liberty's feet up to eye level.
For something to count as a jump,
it must satisfy two criteria.
First, motion must be created by pushing off the ground,
so, a quad-copter doesn't count
because it pushes off the air.
And second, no mass can be lost,
so, rockets constantly ejecting burnt fuel are not jumping,
and neither is an arrow launched from a bow.
The bow would have to come with the arrow
for it to count as a jump.
Many animals jump,
from sand fleas to grass hoppers to kangaroos
and they launch their bodies into the air
with a single stroke of their muscles.
The amount of energy delivered in that single stroke
determines the jump height.
So if you wanna jump higher,
you have to maximize the strength of the muscle.
The best jumper in the animal kingdom is
the Galago or Bush baby.
And that's because 30% of their entire muscle mass
is dedicated to jumping.
This allows the squirrel-sized primate
to jump over two meters from a standstill.
It has like very small arms and upper body
and it's just like, huge jumping legs.
It doesn't have better muscles or anything,
it just has more of them.
- There are some clever jumping toys.
(laughs)
- I used to play with these poppers as a kid
and when you deform a popper,
you store energy in its deformed shape.
Effectively it becomes a spring
and then just like an animal in one stroke
it applies a large force to the ground
launching itself into the air.
(whimsical music)
All elastic jumpers follow the same principle
of storing energy in a spring and releasing that energy
in a single stroke to jump.
But none of the jumping toys we had
could compare to this tiny robot.
(bouncy music)
- Of all the things that I have ever tried to film,
this is the most challenging.
Because it's so small, it accelerates rapidly
and travels a huge distance on each jump.
Each takeoff happened faster than we could even register.
Now, jumping might sound like a niche skill,
but engineered jumpers would be perfect
for exploring other worlds,
particularly where the atmosphere is thin or non-existent.
On the moon with one sixth the gravity of earth,
this robot would be able to leap 125 meters high
and half a kilometer forward.
Rovers may struggle with steep cliffs and deep craters,
but jumpers could hop in and out,
fetching samples to bring back to the Rover.
And you don't lose much energy when jumping,
so if you could store
the kinetic energy back in the spring on landing,
the efficiency could be near perfect.
The team has already started to build an entire fleet
of jumping robots.
Some of them can right themselves after landing so,
they can take off again right away.
Others are steerable.
They have three adjustable legs that allow the
jumper to launch in any direction.
- Essentially, what we've done is
we've added three additional legs
that don't store energy but rather allow it
to form a tripod sort of that allows it to point a direction
and launch in that direction.
- But how does this jumping mechanism work?
Well, the main structure consists of four pieces
of carbon fiber bound together by elastic bands.
Together they create a spring that stores all
the energy needed for the jump at the top of
the robot is a small motor,
a string wrapped around the axle is connected to the bottom
of the robot.
So when the motor is turned on, it winds up the string
compressing the robot and this stores energy in
the carbon fiber and rubber bands.
After about a minute and a half
the structure reaches maximum compression.
How do you know like when to put it down?
- Basically once the bottom there,
sits inward and it can stand up,
right now it would roll over.
- Right.
- Then you put it down.
- Got it. - So as soon as you can.
- And at this point, a trigger releases the latch
that's holding the string on the axle.
So all the string unspools all at once and
the energy stored in the spring is released.
- The jumper goes from a standstill
to over a hundred kilometers an hour
in only nine milliseconds.
That gives an acceleration of over 300 g's.
That would be enough to kill basically any living creature.
- Watch out, watch out, watch out.
- But how does it jump so much higher than everything else?
Nearly 10 times higher than the previous record holder.
Well, this jumper has three special design features.
First, the jumper is incredibly light at just 30 grams.
It achieves this weight by employing a tiny motor
and battery.
Plus its entire structure made of lightweight carbon fiber
and rubber doubles as the spring.
Per unit mass natural latex rubber can store more energy
than nearly any other elastic material,
7,000 joules per kilogram.
And the design of the spring makes it ideal for its purpose.
Initially they tried using only rubber bands connected
to hinged aluminum rods,
but with this design when compressing it, the force rises
to a peak and then decreases.
Just feels like it all of a sudden got a lot easier to pull.
Another design with only carbon fiber slats requires a lot
of force to get started,
and then it increases linearly after that.
There is more and more force required to do this.
The ultimate design is a hybrid of these two approaches.
The benefit being it's force profile is almost flat
over the entire range of compression.
Feels like that needs a lot of force,
and now it feels pretty steady
with the amount of force that I need to apply.
Therefore it provides double the energy storage
of a typical spring
where force is proportional to displacement.
The researchers argue this is the most
efficient spring ever made.
- Sometimes a string will snap,
it's not always consistent that it releases
when it's supposed to.
- Ooh.
- There's a string cut,
let me go re-string it.
(fingers snap)
I'll be right back. - All right.
- You'd probably expect that lighter would always
be better with a jumper,
especially if the added weight is simply dead weight
rather than anything useful like a spring or a motor.
- So we're adding basically a chunk of steel
to our jumper and it's gonna jump higher.
And the key is that we're adding it to the top.
You want your body,
the part that's moving to weigh at least as much as the foot
and when your body's lighter it's basically this collision
this energy transfer is very inefficient
and you don't jump very high.
- But the real secret to how
this jumper can achieve such heights is through something
the researchers call work multiplication, unlike an animal
which can only jump using a single stroke of its muscle,
an engineered jumper can store up
the energy from many strokes or in this case
many revolutions of its motor.
And that's how the motor can be so small.
It doesn't have to deliver the energy all at once.
It builds it up gradually over a few minutes.
So the trade off is kind of like time for energy.
- Exactly.
- And this is possible because
there is a latch under tension preventing the spring
from unspooling until the robot is fully compressed.
Interestingly, biological organisms do use latches,
for example the sand flee,
which can jump incredibly high for its body size.
- It has a muscle that is attached,
let's say right here,
is right inside of the pivot point.
So as it contracts
that muscle the leg doesn't extend, right?
It's actually closing it more,
but then it has a second muscle that pulls it out.
It's going to shift this muscle ever so slightly
outside the pivot point.
That's wild. So there's these two muscles that are working.
- Yeah. So here's your big power muscle,
here's your trigger muscle.
It's a torque reversal mechanism
and then all of a sudden it shoots.
- But even though the biological world has latches
no organism has developed work multiplication for a jump
from standstill.
At least not internally, spider monkeys have been observed
pulling back a branch hand over hand using multiple muscle
strokes stored in the bend of the branch to
catapult themselves forward.
There's a spider that shoots out a silky string
which they pull back multiple times in order
to slingshot themselves to another location.
So it's like slingshotting itself?
- Yes. So they are called the slingshot spider.
- Now I tried jumping in moon boots to see if
they would help me go higher.
- That is okay. (laughs)
- Okay
Ooh.
- And it certainly felt like they did,
but Elliot pointed out that from a standing start
they don't actually help much.
- Like kinda build it, build it, build it, and then go.
- Okay.
Only if you jump a few times before, can you store up some
of the previous jumps energy in the elastic bands and then
that energy helps launch you higher on the following jump.
For years, engineered jumping was developed to
mimic biological jumping, but with work multiplication
it gained an advantage.
If you can generate a large burst of energy
simply by running a motor for a long time
the power of the motor is no longer the limiting factor
The spring is.
So you can focus on making
the most powerful spring possible.
This jumper has nearly maximized the achievable height
with this spring.
Assuming an infinitely light motor
with infinite time to wind up the highest possible jump
with this compression spring is only
around 19% higher than what they've achieved.
If you want to incorporate air resistance
and play with aerodynamics
another way to send the jumper higher is to
make it 10 times isometrically larger leading
to a 15 to 20% higher jump.
- So we're in kind of an intermediate scale where
we still are getting hit by air drag
but it's not as bad as the flee.
If we went 10 times bigger
we could actually avoid drag completely.
- This works since if the jumper is scaled up ten times
on all sides the cross sectional area increases
by a hundred,
which increases the drag force
but the jumper's mass increases by a thousand.
So it has way more inertia meaning
the drag force affects it less.
The entire concept of work multiplication
could bring robots to the next level.
Currently motors and robots have to be relatively small
so they remain portable.
But the simple principle of building
up the energy from multiple turns of a motor
over time would allow robots to store
and then release huge amounts of energy
and set some world records in the process.
(outro music)
Getting this robot off the ground required more
than just engineering.
It took a deep understanding of math and physics.
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