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How does it deform? - Compliant mechanism visualization challenge
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- Опубликовано: 3 май 2022
- This video shows a compliant mechanism that Prof. Hopkins designed as a visualization challenge. Given its complex arrangement of bent-blade flexures, most students can’t visualize how the mechanism can deform. See if you can and then write your answer in the comment’s section below before I show the answer so everyone can gauge how difficult this challenge is for everyone else. Good luck!
The part files for the mechanism can be downloaded from Thingiverse at this link:
www.thingivers...
Acknowledgements:
Special thanks to Ivan Biggs, who helped to fabricate and assemble the design.
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Disclaimer:
Responsibility for the content of this video is my own. The University of California, Los Angeles is not involved with this channel nor does it endorse its content.
Although your shape in the middle clearly gave away the intended motion, from just looking at the shape I thought it would compress axially along the handles. Turns out that was one of the possible unintended motions as you explained later.
I got it but the little circles in the middle was a strong hint. I reasoned my answer from the reflective symmetry
I think it can rotate tangentially to the “socket“ in the center. So if one of the sticks is 90 ° to the ground you could twist the upper stick in the direction the “socket” is flat.
I can't unsee that while turning it the intended way, you're twisting the middle flexure of the three on each side. Maybe even all of them, depending on their exact angles. I didn't think that was the intended degree of freedom for this type of flexure.
Same here
Based on the Freedom And Constantine Topology theory we learned in class, each set of the three bend blade flexures has a constraint space of a plane. The 2 sets create a constrain space of planes intersecting at a line. The line they intersect is the freedom space. Therefore, my guess is that the mechanism can rotate about an axis that passes through the center of the circular part of the rigid body and is perpendicular to it.
I'm so happy the series is back!!!
Your videos are fabulous! You’ve already explained about the The rule of complementary pattern, but I’m still not understand. Could you kindly recommend some articles that I can read? Or make another video? Tks!
"I recommend you put the video on pause" is correct because I got a serious case of vertigo watching that thing spin around wildly as you said that.
dude, your technical vocabulary is stellar, I'd watch just to hear that..
I remember getting this question on my final in the winter, should've guessed it was going to be a video lol
Amazing videos ! Please continue teaching us tips and tricks, creative thinking using this fabulous topic ^^
Or may I say field of research
I am not sure if this mechanism servers as a good visualisaton tool. The way the mechanism bends is different from other compliant mechanisms, which usually have specific joints they bend along. Here, the mechanism features large flexible plates that become twisted along their length, which is not a motion that is nearly as easy to predict as the kinds of compliance mechanisms that I know (which mostly do not twist material around its plane, but just bend it)
I think the bent blade flexures center the handles relative to each other, and the intended motion is like a hand brake - one handle moves forward and back, but it could also collapse sideways
can you do some content about tensegrity joints?
Instead of 3D printing you can use fast version - cardboard, old wine cork (you can cut it with a knife) and pencils. No central "pivot" is needed to it bill be working. BTW - cardboard modeling is a nice and fast, strongly recommended. :)
My guess is that they either rotate (judging purely from the shape of the central wedge) or they linearly slide apart on the depth axis (since they look sort of like balanced/symmetrical leaf springs)...
This is a great little test, which I failed! It is also a very intriguing puzzle that is sure to spark considerable interest.
My best educated guess is that the center cylinder will move back and forth through the “U” shape. I never would have come to the conclusion that it can move. I figure that each set of three flaps can only deform along a line, but since those lines aren’t parallel, it shouldn’t be able to move at all. I even built a lego version of the flaps to test if I could rotate them in a weird way, yet I found nothing. I’m very interested to see the solution.
I love this kind of video.
My guess is, and the shape of the center kinda suggests that as well, that the two pieces can move in the direction of the handles, like a piston, extending and contracting.
- yeah okay that makes more sense
My guess is it pivots like a hinge around that section in the center with the circular part and the semi circle around it
Eu imaginei que ele se deformaria ao longo do eixo central por causa da pista que você deixou naquela junta ali, mas se não tivesse aquele eixo ali, eu imaginaria que o movimento seria o afastamento ao longo do eixo como se fosse uma mola se alongando
My immediate thought was that it could compress or expand but then the circle gave it away and my final answer would be that it can move like a lever!
What are some application for this joint?
I'm guessing the parts can pivot in relation to one another about the axis of the central cylinder feature, but cannot otherwise twist or translate. This is based only on intuitive mental simulation.
I'm guessing it bends side to side, along the axis of the ball and socket parts
The only thing bad about this content is that here isn’t enough of it
I psyched myself out... I thought there was no way it would actually move in that way when someone who sounded like *that* teacher asked.
I thought the trapeziods were moving around the outside, but that's clearly not possible as they are fixed, maybe a rocking of the central joint ?
i think it might twist, possibly with a little side to side motion
damn i thought that middle bit was to throw us off
The socket and ball in the middle give it away, especially knowing they don't touch. The cylindre would be an axis of rotation
I am going to guess that the center slides in and out of the C shaped housing axially
It should move back and forward like a lever. Think sequential shifting gearbox.
This structure deforms into two opposing conic sections with a mirror plane connection .
That's great! But how do you go about designing smth like this?
It’s probably based loosely on another mechanism, figured out a way he wants it to move and designed around that. But the bendy mechanisms can be pretty abstract
My guess: it rotates at a 90 degree angle toward you, if the circular part is in front of you.
That’s awesome
I don't see how it is constrained from sliding along the axis.
A twist motion?
The hinge in the middle gives it away.
I would have guessed "compress and rotate axially."
Interesting that it does not rotate at all.
me too!
Idk looks to me like the sides would squidge out and in, thinner or thicker and rotate a bit forwards and backwards. Honestly it’s way harder to describe with words how I think it moves than visualize it
please slow down the spinning so I can actually look at the mechanism!
My prediction:
The upper handle can deflect about 45* off-axis side-to-side in one plane
If the sockets were spherical instead of cylindrical it should deflect in any plane
I got it even if I know nothing about this type of mechanism.
This is just logical.
This was supposed to be hard ?
I would guess it could twist, but yes this is quite a challenge
Linear rotary motion vertically positive while vertical negative motion os halted
I was wrong yay!
45 degree of not just sideways, like a twist motion.
it moves like a hinge around the center only in one direction
if you didn't include the bearing structure it would have been more difficult
my guess: colinear motion
Ah crap, rotation was my first guess but then I thought he's definitely trying to mess with me so it is probably translational.
So yeah fooled me 🤣
My guess is it rotates and raises
Joint!
Prediction: moving vertically with a twisting motion, like a screw
axially
Flappers will cloese.
Nuh - ailed it 😁
i would say it deforms by torsion and extension.
ok i was wrong lol. i also thought of this deformation, but i thought that the material was too stiff for torsions
spiral unravelling into plane
i got no idea
My frist thought was correct but then I thought it was trap
Quick guess is that it actuates like a universal joint. Let's see
I was kind of wrong. Great video!
I think it will twist sideways
I was wrong
a simple 2d joint.
its a hinge
Well that was easy XD
Pivit
It is not as hard as i thought.
AAAAAAAA STOP SPINNING