“Binary Stiffness Compliant Mechanism EXPLAINED” - Binary Stiffness (Part 1)
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- เผยแพร่เมื่อ 22 ก.พ. 2021
- This video depicts a translational binary stiffness compliant mechanism that achieves two different states of stiffness by being triggered using a simple switch. One state is very compliant while the other state is very stiff.
Details about this video are published in the journal, Extreme Mechanics Letters, and can be found at this link:
www.sciencedirect.com/science...
A raw video of this mechanism was previously uploaded to my student, Reinier Kuppen’s, TH-cam channel,
/ @reinierkuppens
but this video is intended to explain the mechanical principles behind how the mechanism works.
The part files to 3D print this mechanism can be downloaded on Thingiverse at the following link:
www.thingiverse.com/thing:543...
This video is the first part of a five-part mini-series about binary-stiffness compliant mechanisms. Be sure to watch the other parts to learn more about how they work and for what applications they could be used.
Also, to understand more about compliant mechanisms in general, be sure to watch the other videos in my Compliant Mechanism Design series on this channel.
Acknowledgements:
This video would not have been possible without the brilliance of Reinier Kuppens, who designed the mechanism, so a huge thanks to him for the great work he did in my lab at UCLA! And although we jointly own the copyright on this material, I’m grateful to him for giving me permission to publish about the content.
Donate to help support my channel:
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PayPal.me/FACTsMechDesign
Thank you for your support! It is much appreciated and helps enable me to make more content.
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.
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Honestly this series doesn't get enough credit for how awesome it is. This is very educational and interesting that it explains a popular trend going on right now. Thanks for the hard work, keep it up guys!
Additioinal comment: The "negative stiffness" wasn't immediately intuitive so I had to think about it a little bit. Once triggered and then deflected laterally, there are 4 elements involved in bending and/or compression/tension. The 2 vertical elements are strictly in bending and fairly linear, with stiffness of 12EI/L^3. The 2 "truss" elements are the key to the negative stiffness. When the meachanism is "set" the 2 truss elements are buckled and in compression to hold the deflected position. As the mechanism deflects to one side one truss element lengthens and the other shortens. Elements in a buckled shape are not linear when they shorten or lengthen, requiring less force to shorten than the amount of force they gain when they lengthen. This change in force of one vs. the other is what provides the negative stiffness. IOW if the vertical elements were removed, or made longer/thinner so they offer less resistance, I believe the mechanism would actually be laterally unstable meaning when it was set it would want to also deflect left or right and hold that position. (Actually I think "negative stiffness" is somewhat the definition of unstable.) The mechanism as pictured is somewhat balanced so that the straight vertical elements have just enough stiffness to brace the 2 bucked truss elements that want to make the mechanism buckle laterally.
You mentioned Part C of episode 3 on this channel, however your latest video prior to this one was Part B. Do you have another channel, or are your videos available anywhere else?
This series is so fascinating and educational. Thank you for posting it! Keep the video’s coming.
I just stumbled upon your series and it is amazing! Thank you very much for all the hard work you (and your students) have put into this!
Strong start to the series!
Fantastic and very well explained!
Fantastic, keep making these videos.
Stumbled on this video!
I know this guy from my old university (TU Delft, the Netherlands), used to get lectures from here when he did his PhD. Cool!
Totally awesome!!! Those two critical forces that pulls-straight & pushes & bends are well explained. After watching your videos I am beginning to realize that there maybe a way to categorize those complex-degrees of freedom of motion concerning the RNA and DNA molecules volumetric displacements, sorta like mapping the "mechanical codes" of both the RA and DNA molecules!
Great and inspiring video! Your videos inspired me to order 3D printer and to start working with compliant mechanisms on my own :) Thank You!
The 3d printers aso so useful, you can do almost everything
It is interesting that the mechanism can trigger itself. Of course in the untriggered state where the restraint is primarily due to truss action, the truss can't deform significantly unti lone of the elements buckles, and as that element buckles the tension in the other element pulls on the switch to trigger it. This type of behavior can happen in buildings with steel braces during seismic loads where one brace will buckle and lose its stiffness while the brace in tension maintains its strength and starts pulling on something else. (I'm a structural engineer and I understand completely how this is behaving, but it is still very interesting to watch.)
You had me at “Binary Stiffness Compliant Mechanism EXPLAINED”... jeje
Thank you for providing the paper without a paywall!
wow, inventing the cricle all over again is very impressive
Really interesting video... 👍
It's amazing to be witnessing a whole new science. It's like microcomputers in the 80s in that it's accessible to almost everyone and the floor is littered with innovations just waiting for someone to pick it up and run with it.
May I present you the wheel, another whole new science
Everything was created in beautiful and most effective way. Why!
Because the creator is The Affectionate and have the knowledge of all things.
He gave us physics to show us how hard and beautiful his creation is, So we love him for giving us all of it.
I saw it and immediately knew how it worked but the terminology was completely new to me
so awesome.
What a great idea! This seems like a solution without a problem but I can guarantee we can find many purposes for this invention. The comments alone in here have a plethora.
I had scales come to mind. Lock for transport then unlock for weighing things. And that’s about all I can come up with. Doesn’t have enough movement to be 3d print or to be suspension components.
Just thought of the best use for this!! Very interesting possibilities!
Very interesting
I found a gem channel now :D !
This would be great for a "hidden lock" button. The shuttle i.e. the router of the lock, could be locked/ fixed until the "button" is pressed freeing the lock.
Varying degrees of on and offness at last, love it. Look at the J banned suspension from f1 you will like it.
I would have said that the tension of the angled blade flexures (one or the other depending on direction) is the primary limiting condition resulting in stiffness when the bistable switch is in the "stiff" position. The animation showing strain curves of the "truss" arrangement appears to ignore the possibility that the material may not have enough elasticity to stretch as depicted.
so with a well calculated lever you can use that as a resettable overstrain/out of bounds flag, though that can trivially be done with strain gauges and software, the fact that it becomes loose is useful compared to a stiffer mechanism, and it doesn't require energy.
I can see it used as resettable a pressure safety valve for example, where the arm is connected to a plunger, and if the pressure is too high or too low it triggers, allowing the pressure to equalize
I was viewing this as a "mechanical switch". So when set the input force can go through the mechanism and create an output force, but when not set the input force cannot go through it. This sounds like the mechanical equivalent to a transistor. So if multiple transistors can be configured to form electronic circuits for adding and so forth, it would follow that a group of these mechanisms could be combined to to digital computations.
And good Old tried and true micro switches
Can you make a variable stiffness
Nice
Anyone have ideas on practical uses for this?
Wait, the button at the bottom is also bi-stable isn't it? The part with three fins on each side.
I guess this would be useful for analyzing structure failure.
This is a very interesting design. I'm confused, however, about the claim that was made at 1:00 that the shuttle is constrained by the parallel blade flexures to move along one axis (the one perpendicular to the face of the parallel flexures). I would expect that shuttle to follow a circular path since the parallel flexures are fixed at one end. This is because the shuttle would rotate about the points at which the flexures are fixed. In fact, you can see this circular motion at 4:28 to 4:34. As the shuttle moves, it gradually comes closer to the wall on which the flexures are fixed, meaning that the shuttle moves along two axes, not along one. Maybe I'm misunderstanding the motion constraint, but understanding this would be very helpful, since I'm trying to build a uniaxial compliant stage.
The range of motion is small enough that it’s basically linear
Would this be considered a 2D (2 dimensional) "tensegrity" mechanism?
Yes, as it is held together by tension in the stiff state. However the compliant state is like adding slack to the lines of a tensegrity, rendering the model useless
0:40 "calm-ponent"?
Banger outro song, what's the name?
I have search it with Shazam and it's "The follower - 7 Minutes Dead"
Fascinating. Would have been nice to include at least a couple examples of application for this gadget as I can't visualize anything it could be used for.
Yes that video is coming soonish so stay tuned!
@@TheFACTsofMechanicalDesign Awesome. Look forward to it, I'm sure it'll be quite interesting.
Im no engineer but the easiest thing I can think of is a mechanical overload (or stress) safety switch, like the ones in a circuit breaker more or less (in function not mechanics). IE too much pull causes the bi-stable switch to detract removing power from whatever device its attached too. Admittedly not a very creative idea on my part, but it'd work.
@@thartwig That makes sense but then I can't think of a mechanical system that should hold firm but releases and flexes if the strain becomes too great without causing more damage to whatever was relying on it to hold firm. Maybe like a torque wrench type device?
@@darioinfini i was actually thinking heavier machinery and as a safety mechanism for the operator, to prevent injury or catastrophic damage to equipment. I look forward to seeing what they come up with though!
I am probably not the first person to think this, but I wonder if it would be possible to build a flexture that mimics binary logic gates. Making possible a physical force driven computer. My guess is yes, but it wouldn't be as fast as an electronic computer.
Before the Transistor, Yes, And, Not, Nor & Nand gates, there were Relays that performed similar tasks. A plethora of relays clicking and clacking to do this and that. In large automatic machines like lathes, mills, ect, I was amazed at all the action the relays, capacitors, wiring were doing. I think your suggestion is possible.
It’s possible but it would be super slow for a pretty long time probably. I mean electricity on computers goes 90% the speed of light. Hard to get anywhere close to that mechanically. But yeah you could probably make a computer. Another problem might be a buss. how would you be able to hook each component up and transfer the data. it wouldn’t work like an ordinary computer. But I don’t know that much about any of this so idk what this even is. I just know a tiny bit about computers.
The question "how does it work?" simply amazes me: *it's DOING it right in front of your eyes* - the V-oriented members are turning from a push-rod state into a leaf spring state... why don't people trust their eyes any more but demand "an explanation"??? This appears to be a modern phenomenon, also reflected in the behaviour of my students in an increasing inability/unwillingness to find their own path to a solution...
@@creamwobbly I guess it's safe to assume that you felt personally attacked by my observation that there is a visible decline in people's "confidence in their own analytical capabilities." Please note that I was trying to be nice and didn't say that laziness is the reason for this new ignorance.
resetable load measuring device
Which software could be used for simulate the movement of compliant mechanism? thank you.
Hi UD MV, any finite element software package with structural analysis will do the trick. For example COMSOL, ANSYS, ABAQUS, but also many cad software programs have basic FEM functionality these days.
@@ReinierKuppens Thanks so much for your reply!
it's a bit simple, but for something like this you can use algodoo, and use pivots with a springs for bars, and ropes for the buckling system.
tbh it's not that great, but if you just need to test the mechanincs it'll do the trick.
just like a transistor
Compliant design is the future!!! Although I can see clearly the how it works the computational side is beyond my skillset at this moment. Suggestions on how to acquire these skills, Videos, books, online classes, would be appeciated.
More please. [NomNomNom]
Perfect for earthquake constraints
what material is it ?
It says it’s PLA in the video
Interesting, but how is this better than anything that already exists? Like hydraulic cylinders with control valves? Like those found in bicycle forks.
Круто
How about this explanation. The wires are bend but they are not stretchy. It allows any kind of movement as long as we are not stretching any wires. At the stiff position to allow any kind of movement we have to stretch the wires. When we apply a large enough force to bend the 6 horizontal wires it goes to the compliant position. Compliant position allows movement in a region where we don't have to stretch any wires.
Yeah, that's much more straightforward. PLA only has a tiny bit of stretchiness.
And why do we need this again?
Yo I can imagine this with some heavy modifications being used as a cheap way to have ""adaptive"" suspension damping in some vehicles!
Welp, time to make mechanical transistors and really loud computers.
I had an idea that can make anyone bilionaire with it.
wait what? i am struggling to imagine the possibilities
i have the same mechanism in my pants
Very interesting and fun to watch. But please please remove this annoying background music. It just lowers signal to noise ratio.
at some point we'll have to play background music during school and university lectures
WHY!?? ... What's the relevance at all in making something so complicated but no one understands it's purpose. Where is the passion? What problem is being solved??
I think it got a purpose, idk what, but I really think this thing can be useful on something
I think it just might be a generalized demonstration of a mechanism that could be used in designing something else, not a invention with any use of it's own.
All those force graphs are idealizations, linearizations, approximations... and overall hiding more of what's going on than they show.
That yellow graph @2:30 is absurdly scaled up compared to the situation before. In reality it is pretty much 0 everywhere.
That blue graph @3:02 is not linear in reality, with a flat tangent in the origin.
So you add 0 to 0 and sell it as sliced bread that the result is also 0. SCIENCE! :D
I'm not sure you criticism is important here? It's an explanation pitched so that anyone with a reasonable grasp of school maths can follow. The assumed linearization is just normal engineering approximation - it's accurate enough to describe the system's behaviour acceptably well.
The one bit that does bother me is the claimed and visualised (near) 'zero stiffness'. 0.08 N/mm is roughly equivalent to 8g of weight in standard gravity per millimetre of travel, which is definitely perceptible and clearly enough for the mechanism to self-center when released.
Yes, it seems the motivation to introduce the concept of negative stiffness may have been stronger than acurately answering the "how" question.
Imagine trying to explain this to anyone in the world who simply had no clue what your saying. 😂 My girl ran over to see ehat the hell i was watching.🤣 She was like what the hell are you watching. I know what she 🤔 but come on now. This is like the episode of the Fluxencombinator. Some people really are not able to handle intelligent and technical descriptors.
*can’t easily move.
In the beginning was the Word, and the Word was with God, and the Word was God. 2He was with God in the beginning. 3Through him all things were made; without him nothing was made that has been made. (John 1:1-3)
skip the noisy music, it degrades information quality.
You can literally achieve the same function with a stick and a hole.
Look, I push the lock in, the door does not open, but if i push the lock out, you can move the door freely...
These people literally have too much time on their hands.