What do this satellite thruster, plastic tool
and micro mechanical switch have in common?
They all contain components that bend
so-called compliant mechanisms.
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Now about a month ago
I was giving a talk in Utah hence the suit
and that’s where I met this guy
Larry Howell, professor of mechanical engineering.
So it’s always been considered to be bad to have flexibility in your machines.
We’ve tried to take that thing that everybody hates, that is trying to avoid
and say how can we use flexibility to our advantage?
How can we use that to do cool stuff?
Now Professor Howell literally wrote the book on compliant mechanisms.
That‘s the most cited book.
But he’s pretty nonchalant about his work.
Just watch how he introduces this mechanism
he developed to prevent nuclear weapons from going off accidentally
Actually in safing and arming of nuclear weapons.
And so if…
-所以 如果 -啥？
Hang on, hang on hang on
-What-ing nuclear weapons?
-Safing and arming -Safing and arming
Yeah so if there’s anything in the world
that you want to be safe It’s not going to accidentally go off.
I feel like this is, it doesn’t even need to say
but yes, nuclear weapons obviously, you don’t want them to go off.
What I don’t understand how this is gonna keep the nuclear weapons safe.
Now I want to come back to this device and explain how it works
Once we understand why compliant mechanisms are best suited to this task
So let’s start with something basic.
Probably the first compliant mechanism I ever designed wasthis thing.
What it is is a compliant mechanism that is a gripper.
So you can put something in there
It will get actually a really high force.
I can put that in there
and it breaks the chalk
What have you put your finger in there and squeeze it?
You would scream in pain
Would you like to try?
I would like, I would actually like to feel the force
OK, you need to squeeze it yourself though or it’s… -Really?
-那你得自己按下去 否则…… -真的？
Well all right, I’ll squeeze until you scream in pain
-好吧 你喊疼我就停 -别……
That very quickly got incredibly painful.
It felt like having my finger like in a in a vice.
That looks suspiciously like vice grips.
but now with these flexible components where the hinges are.
What I learned in my visit with Professor Howell
is that compliant mechanisms have a number of advantages over traditional mechanisms
But I thought he needed kind of a clever pithy way
to remember all of these advantages.
So I came up with the eight pieces of compliant machanisms
and the first of those is Part count.
Compliant mechanisms have reduced part count
because they have these bendy parts
instead of having things like hinges and bearings and separate springs.
This gripper is just a single piece of plastic
but achieves a similar result to the much more complicated vice grips.
Like how much does it amplify the force?
This will get about thirty to one
so I could get for one pound force in, get thirty pounds out.
That’s pretty good. It seems like that would be super cheap.
And really inexpensive, so this we just made here in our shop
but you can imagine also injection molding that
-That would cost like cents -Yep, this would cost cents
-成本只需要几分钱 -对 只要几分钱
The other thing is because of its shape
you could extrude it and then just chop them off.
That would be cool.
So the simple design allows different production processes to be used
which lowers the price
These switches, for example, achieve in one piece of plastic
what is normally done with springs, hinges and many rigid plastic pieces
-also a good fidget device -How long can these last?
We’ve had these in our fatigue testing machine.
We’ve been able to go over a million cycles without failure
-What have we got there? -All right, Derek I’ve got a quiz, quiz for you.
-这是什么？ -好了 Derek 我要考你一个问题
Okay, I’m gonna -elephant！
-那么 我要…… -大象！
Okay I’m gonna push on elephant’s rump, this direction okay?
I’m gonna hold this
and that little dot right there, is that dot,
when I push on it,
is it gonna go left, right, up or down?
请问这个它会向左 右 上 下哪个方向移动？
I just, you know what, I wanted to guess without even thinking about it?
Yeah, please do.
-I’m gonna say like up and in -okay, up and in
-我觉得会向内向上运动 -好 向内向上运动
And I kind of feel like that because like that would be a logical way
for an elephant to hold its trunk -okay
but also because like, if this is all going over
I feel like this is gonna kind of extend there
and that’s gonna get pushed up in there.
-Ah, good thinking well -I don’t know, is that good thinking?
-想的不错 -我不知道 刚刚我说对了么？
That’s well it’s thinking at least. So…
还不错 这至少是个想法 嗯……
This is designed so that when you push on that
it actually just rotates in space.
It doesn’t move at all.
I knew you were gonna pull some sort of trick
it’s a trick question!
now since I was fooled by it
I had to try it out on my friend, the physics girl.
That’s so trippy.
-That is so cool! I don’t understand What!
it’s modeled after the mechanisms you use in wind tunnels
where you want to have, say, a model that’s that’s attached here
but you move it
and all you want to do is is control its its angle and move it around in a wind tunnel.
don’t displace it but be able to change the angle.
Devices like this demonstrate that
compliant mechanisms are capable of producing very precise motion
which I personally found pretty counterintuitive
because these objects are made up of flexible parts
but maybe that shouldn’t be surprising
because compliant mechanisms don’t suffer from backlash for one thing.
So backlash occurs when you have a hinge
which is basically just a pin in a hole
and it’s moving in one direction
and now if at some point the motion reverses
it doesn’t happen instantaneously
because there’s some give in the hinge.
This also causes wear and requires lubricant
and that is why compliant mechanisms
have better performance than their traditional counterparts.
This one though is my favorite.
That is is one of my favorites too.
It’s just so pleasing, right? Ahhh,
that sound is so satisfying.
This actually, believe or not
was inspired when we were doing things at the microscopic level
where we’re building compliant mechanisms on chips
We had to be able to make these compliant mechanisms out of silicon,
which is as brittle as glass.
which is as brittle as glass.
it’s crazy hard
But that also means once we figured out the design
we could make it in a material even like PLA
which is also, you know, not the ideal compliant mechanism material.
So you can get on our website
and get the material… and get the files to make this yourself
I’ll put a link in the description
That also has a nice feel and nice snap to it
It has a really nice snap. I like when it comes out,
It’s like“gunk” , you know, there’s something about that that’s really it’s very pleasing.
So these things actually move?
Oh yeah, yeah yeah
是 对 没错
-I need to see this okay -all right we’ll do it
-我得看看 -好呀 我们来试试
Were those etched on there?
Yeah, those are etched and so just using the same process as used to make computer chips.
So another advantage of compliant mechanisms is
that they can be made with significantly smaller proportions
because they take advantage of production processes like photo-lithography
And we have motion that we want at the microscopic level.
Plus, since they simplify design,
compliant mechanisms are much more portable, meaning lightweight
which makes them perfect for space applications.
This here is something we did with NASA making a hinge
that can replace bearings for say deploying solar panels.
This is titanium, 3D printed titanium.
But what’s freaky about it is
you get that motion which people expect
but there’s a piece of titanium that can bend plus minus 90 degrees,
That is solid titanium.
That is one piece of titanium that is 3d printed
-There’s no alloy, nothing to make it flexible. -Yep, this is, yeah
-没有加入合金使它变得易弯曲 -是的 没错
And even freakier than this is this guy right there.
So that looks like a crazy beast
but every part in there has a purpose.
All these flexible beams, here are the two inputs
And again we did this with NASA for a thruster application
where you can put a thruster right there
and now with our two motor inputs
we can direct that thruster in any direction.
That titanium device moves that,
you notice, that’s just all bending
and then there’s no pinch points for the fuel lines or electrical lines coming in.
Here, this single piece of titanium allows you to use one thruster
in place of two.
Okay, that is a clutch
So the idea is if you spin it up really fast
because it’s flexible, this outer part will actually start coming outwards
and then if there’s a drum around it
it’ll contact with that drum and spin that thing
Oh, so this like kind of, oh!
That kind of comes out, like so
When it gets spinning really fast
and then you’re essentially engage this outer drum
This is like the way that a chainsaw would work or something like that
because you get it spinning fast enough
and it engages the chain and then it turns over
-Centrifugal force, Wow, that’s cool
离心力 哇 那太酷了
So here this is made of plastic, you can see it
But in reality it’s gotta be a lot stiffer
so here it is made in steel -What?
So hang on, you’re saying that that thing, which is made of steel
-Yep -You spin it up to a certain speed
and then it expands and engages a drum that is around it
-然后它向外伸展 卡住滚筒 -对
-Yep -So idle with no motion
but then at a certain speed that are what we designed it for
It will speed up to that rpm
-You speed it up and it engages -Yup
-你给它加速 然后它带动其他部件 -对
I had no idea like I have learned something today
So let’s come back to the safing and arming device for nuclear weapons.
Its purpose is to ensure that no random vibrations, say, from an earthquake
inadvertently disable safeties and arm the nuclear weapon
Now one of the requirements was
that this device be made as small as possible.
They had made those as small as they possibly could using traditional methods
even using things like what the Swiss watch manufacturers were using.
With compliant mechanisms they produced a device out of hardened stainless steel
where some components were the size of a human hair.
This is high-speed video
Here the device is operating at 72 Hertz
meaning this little hole makes two complete revolutions each second
The way it’s meant to work is an arming laser shines on the rotor wheel
and when the proper input is given to the system
the wheel rotates a notch.
If all the proper inputs are given
then the hole lines up with the laser beam
and crazy things happen from there.
So it is essential that this device’s performance is perfectly predictable
even if it sits unused in a silo for decades.
So are these now being used on nuclear weapons?
You know, it turns out that they don’t tell us what they do with their nuclear weapons
So we design them, we made prototypes we tested them
我们只是设计出来 做出原型 进行试验
and then it goes what they call behind the fence.
And…where it’s all classified and, you know
We don’t know what happened, so…
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What do this satellite thruster, plastic tool