Compliant Spherical Mechanism: A Flexure-based Kinematic Sculpture
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- Опубликовано: 27 апр 2022
- This video introduces a compliant three-degree-of-freedom (3 DOF) spherical mechanism that uses the collective deformations of blue flexures to ensure that every point trajectory on both its white dome-shaped frame and attached yellow probe lie in concentric spherical shells around a single stationary point (i.e., the center of the probe’s sphere). The mechanism was designed as a vibrating compliant kinematic sculpture to mesmerize students that poke at it.
The flexures used were adapted from a design proposed by Professor Just Herder’s group from Delft University of Technology. A link to their paper published in Precision Engineering is provided here:
www.sciencedirect.com/science...
Also see this related video: • New spherical flexure ...
The link to Thingiverse to download the STL files necessary to 3D print and assemble our mechanism yourself is included here:
www.thingiverse.com/thefactso...
Acknowledgements:
Special thanks to the following individuals, who helped to fabricate and adapt the design so that it could be fabricated for my Compliant Mechanism Design course:
Allaine Taduran, Alyssa Tomkinson, Feng Xu, Jiahui Xi, Justin Tang, Katusch Strich, Lily Tebb, Mingzhang Zhu, Mukesh Yadav, Noah Truong, Roger Truong, Sean Velandia, Shubham Wani, Varit Vicathorn, Weiqi Wang, William Xu, Yurika Yamada.
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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.
So that was really interesting the second time I watched it, the first time I was waiting for you to call it prefamulated amulight.
First time I thought it was a demonstration of how side fumbling is effectively prevented in the waneshaft.
Thank you for explaining the converging geometry of the flexure.
For a moment there the narrator almost sounded like the “Turbo Encabulator” guy lol. Excellent presentation nonetheless.
Flexures are so interesting. Thanks for sharing this. I'm printing another model I found on this channel right now.
This make my brain compliant
excellent! as usual... my sincere respect. following you.
Ooooooh that's my statics professor! Awesome!
He looks more dynamic than static.
You know what this reminds me of? Lol..
My newborn niece’s head :))) since her neck muscles is not strong enough yet she cannot hold her head in a stable position and I think her skull share the same DOFs with this kinematic sculpture 😅 & she obviously has a nerd aunt ☺️🙈
that is really cool! would be interesting in coupling it with an actuator
Very clever mechanism, and a very educational video. The principle of the bend axes of the flexures intersecting at a common point feels like a very general principle that I can apply in my own flexure designs. Thanks! (I especially appreciate you providing the STL files for the mechanisms you create.)
(Would it also be possible for you to post the CAD files themselves, so we can play with them or incorporate elements in our own designs? F360 would be preferable for us hobbyists, although I suspect you use Solidworks yourself…)
Sick!
I literally thought it was a computer simulation at first. Thats cool!
I remember printing one of those modules - super cool.
This should also work with 3 instead of 4 flexture modules, right?
Yes and two. Three is awkward because then they don't interlock. I did four to hold it up and get a cool interlocking look
That is so awesome! It reminds me of a hip ball joint. I want to 3D print this over the summer. Can the thinigiverse link be fixed?
I am unsure exactly what it is about compliant mechanisms that make me angry. I realize they are a good idea. They're elegant and I see the benefits. I think it's because I feel like we've spent a long time as a species fussing over joints and parts and oiling the points where things connect and this and that and the other thing.... when we could have just been like "oh, bendy thing no break herp derp"
They aren't equivalent, a proper spherical joint is very rigid and can take significant loads. Flexures like this have very limited rigidity, it would be easy to move the sphere away from the centre of rotation with little force. Much more useful for applications with negligible loading where a part cannot be mechanically constrained.
What about fatigue fractures? How do compliant mechanisms deal with it?
Is there any video on flexure U join designs? I’m trying to make 3d printed 2dof load cell
Hypothetically, is it possible to use this design for the manufacture of a seismic sensor?
Awesome tech. Thingiverse link is broken though
Yeah that is right... what gives?
how could or would you mechanically control these though?
How do those flex modules prevent up/down movement? And if they can't do that, then it isn't going to be able to keep the small sphere in a single location.
They can do that - each blade is very stiff in the width axis compared to the flat axis. With the flexures bent along an angle like they are, it means that any translation of the center point of each flexure will be accompanied by the blades' stiffness effecting a rotation in the center point as well. You can overcome that if you can overcome the strength of the blade flexures, but the point of the device is it's just easier to move individual flexures while inducing that ideal rotation around the centerpoint than not to. Combine multiple flexures together and you end up with a device that's pretty well constrained in translation but very poorly constrained in rotation.
This is quite an ingenious mechanism! Does it have any known or plausible applications?
Aiming of gamma ray beams for treatment of cancers.
Ball joint on wishbones of a car which lasts forever
@@predragbalorda It does look like it would be quite a challenge to get it small enough to have the same packaging efficientcy. You might just end up with a lot of very small precision parts to replace what is essentially just a ball, which can be turned out rapidly on a cnc lathe.
@@PartykongenBaddi 3 parts to be exact. Also a ball requires lubrication due to friction between mating surfaces and the ball(s). This thing has no moving parts ergo lasts forever (or untill material fatigues enough to break). There is a reason they use flexures on the JWST.
Don't get me wrong I get your point but different requirements for different usage scenarios - minimal servicing means flexures.
@@predragbalorda i was just thinking of how small this would be to replace a bearing with 14mm outer diameter as some of the spherical bearings we use in small car suspension are. Those are also maintenance and lubrication free by use of teflon composite bearings.
Bobble heads will never be the same.
Super cool! I printed this but the Base_1_V3.STL file is empty, can you please repost.
All that time and effort building Airfix kits when I could have just used an animated sequence to put them together. 😂
Damn, the thingiverse link is 404'ing. Did anyone get the files?
No!!
Why do so many of these flexure based mechanisms use a combination of straight blades and sharp corners instead of curves?
Based on the geometric explanation of this specific setup, I would guess it is analogous to the static index of refraction in most manufactured products.
Sure you could possibly have a continuous solution … but it might be significantly more complex to fabricate (in terms of the technique) or necessitate tighter tolerances.
In this example they used four fexures. But wouldent three already be enough?
Yes. And actually 1 would be enough although it wouldn't be symmetric. Two would be symmetric and may be best for practical application. We picked four to do the cool interlocking design and to be able to hold up the weight of the heavy dome. This piece was more of an artistic sculpture than a practical machine
The chroma keying used seems really off for some reason.
Enhanced bobble head
Not seeing how this prevents translation along the x, y, or z axes--which would push the probe tip out of alignment
The blue triangle bits have all of their faces oriented to pass through the center, and with all of those creases each face can only move/flex in sphere-tangential directions. None can move radially towards or away from the center. (Judging from the video the center tip does appear to jiggle slightly.)
@@jacobolus Thanks. And yet, that's an awful lot of material: a small flex along each joint in that path could represent a fairly large overall deflection. I'd be curious to see a stress/strain plot for translation.
Were printed on various prusa printers "shows an ultimaker" 😅
N64 controllers sticks would never wear out
4 springs to restrict 3-DoF - - isn't this overconstrained?
..1:27 looks like an Ultimaker ;) not Prusa..
You probably saw this already, but just in case: ruclips.net/video/HXB925ptd7Y/видео.html&lc=UgyuoV7ubEDfYNtLvP94AaABAg.9aP8Lj2ct0G9aPZbb6xlTO
"Yes. And actually 1 would be enough although it wouldn't be symmetric. Two would be symmetric and may be best for practical application. We picked four to do the cool interlocking design and to be able to hold up the weight of the heavy dome. This piece was more of an artistic sculpture than a practical machine"
Very cool, but its not perfect there is too much slop you can see the ball is displacing on Z and X axis when moved.
Haven't anybody noticed that its not holding the position of that sphere in the same spot all the time? It's not much but that is visible on the video so it must be couple of millimeters so not enough to get this doing any useful work I think
It's a flexture. It's not for precision.
Very much depends on what 'useful work' is here. As shown, it won't give submillimetric precision - but there are a lot of areas where that is absolutely sufficient, especially when combined with the other advantages of compliant mechanisms.
Also, it depends on what materials you use. PLA will flex in ways that e.g. spring steel will not.
@@Barnaclebeard I can't really agree with that. Flexures are all about removing any lost motion and reducing or eliminating friction- those are key attributes in 'precision applications' I've known them in classical precision Instrument design, not much in power transmission.
I was wondering if this could be adapted for use in an astronomical mirror mount whiffle tree. You want to have each contact point on the back of the mirror not introduce stress via friction/stiction, but allow some lateral movement and no vertical displacement.
@@autochton This is a good suggestion but I can't fully agree cause what I see here is rather few millimeters than submilimeter. There are obviously some applications that this would be enough but at the same time lots of limited ones
You made a nice video and it demonstrate well what you wanted to show. But the construction is heavily over constraint. Which is sad because if the principals of flexure design would have been followed, it would have been well designed.
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three-dimensional spatial space none inertia gyroscope .
gay