Name: 為什麼能彎曲的機器更好？ (Why Machines That Bend Are Better)
Uploaded: 2021-01-14T10:25:34.000Z
Duration: 12 min 52 s
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What do this satellite thruster, plastic tool, and micro mechanical switch have in common?

Well they all contain components that bend, so-called compliant mechanisms

基礎被動語態

This episode was sponsored by SimpliSafe. More about them at the end of the show.

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 in your machines. Well we've tried to take that 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

actually in safing and arming of nuclear weapons.

And so if you want.... -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 saying but yes nuclear weapons obviously you don't

want them to go off. What I don't understand how this is gonna keep the

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

[that's cool] So let's start with something basic.

compliant mechanism I ever designed was this thing. What it is is a compliant

mechanism that is a gripper so you can put something in there and it will get

actually a really high force. I can put that in there and 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?

well all right, I'll squeeze until you scream in pain

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

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 eighth P's of compliant mechanisms 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

you could extrude it and then just chop them off and that would be cool.

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

-we've had these in our fatigue testing machine. We've been

able to go over a million cycles without failure

quiz for you okay, I'm gonna  -elephant I'm gonna

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

I just you know what I wanted to guess without even thinking about it?

I'm gonna say like up and in -okay  -and I kind of feel like that because like

that would be a logical way for an elephant to hold its trunk -okay

if this is all going over then I feel like this is gonna kind of extend there and

that's gonna get pushed up in there. - ah, good thinking

good thinking? that's well it's thinking at least so... 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

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

be surprising because compliant mechanisms don't suffer from backlash

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

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.

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為什麼能彎曲的機器更好？ (Why Machines That Bend Are Better)

fatigue

incredibly

engage

material