
Tensegrity - ics
http://en.wikipedia.org/wiki/Tensegrity
======
Animats
Designing structures such that all elements are either in tension or
compression, with no bend moments, used to be very important in the era of
iron bridges. Truss type railroad bridges were built that way. Often the
joints were actual pins, so that no bend moment could be applied at a joint.
Iron didn't handle bend moments well, but cast iron could handle pure
compression and wrought iron could handle pure tension.

Steel is equally strong in tension and compression, and once good steel became
cheap, structural design was much less constrained. (Mass production of steel
came later than is generally realized. Until about 1890, good steel was about
as rare as titanium is now. Steel swords go back a long way, but I-beams
don't.)

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gkop
Probably the very coolest way to set up a hammock:
[https://www.youtube.com/playlist?list=PL4IGA3iO2R62SAhLcIbKE...](https://www.youtube.com/playlist?list=PL4IGA3iO2R62SAhLcIbKE2fCAcXbY-1K9)

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whiddershins
there's a cool book called Anatomy Trains that analyzes the elements of the
human body as forming a tensegretic structure, rather than a compression
structure. So don't think of all the bones stacking on top of each other like
stone, but instead being held in constant tension by muscles and ligaments.
Also in the introduction it shows you how to make a tensegretic tetrahedron
out of chopsticks and rubber bands. Pretty good stuff.

[http://www.anatomytrains.com/fascia/tensegrity/](http://www.anatomytrains.com/fascia/tensegrity/)

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nazca
I just bought a "Tensegrity" tent... it isn't pure tensegrity (there is one
small bent pole) but it gets close.

[https://www.sierradesigns.com/product/tensegrity-2-elite](https://www.sierradesigns.com/product/tensegrity-2-elite)

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ealloc
What happens if a single cable snaps? It seems like all the strucutral members
in the network will then experience a "bending moment", yet the structure
depended on the lack of bending moment for rigidity.

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nvader
Reminds me of the Stick Bomb.
[http://en.wikipedia.org/wiki/Stick_bomb](http://en.wikipedia.org/wiki/Stick_bomb)

~~~
throw_away
from the references:
[http://lunatim.com/kinart/stickhistory.htm](http://lunatim.com/kinart/stickhistory.htm)

this is amazing. now I'm strongly resisting the urge to order a couple hundred
tongue depressors.

~~~
ars
> now I'm strongly resisting the urge to order a couple hundred tongue
> depressors.

Give in:
[http://smile.amazon.com/gp/product/B0033F7YQW/](http://smile.amazon.com/gp/product/B0033F7YQW/)

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gdubs
I went through a period of being obsessed with Buckminster Fuller's work. I
took a trip to Montreal to visit the Canadian Centre for Architecture a while
back, and at the library got to view this old construction kit called
Tensegritoy. [1]

1:
[http://tensegrity.wikispaces.com/Tensegritoy](http://tensegrity.wikispaces.com/Tensegritoy)

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andrewliebchen
Diller + Scofidio's Blur building ([http://www.dsrny.com/#/projects/blur-
building](http://www.dsrny.com/#/projects/blur-building)), in addition to
being an awesome environmental experience, was a tensegrity structure.

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lotsofmangos
Cellular cytoskeletons are another interesting area to look for these kind of
structures.

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kristopolous
There's a lot more to this... I've been a fan of these studies for a long time
in the way of holistic dynamic analysis of systems - problems that usually get
a statistical analysis approach. I think there's another school of thought
that can lead to higher fidelity predictions - and these tensegrity systems
are examples of that nonformalized and unstudied school.

Although these systems can be treated through classical analysis, there's
something a bit more compelling about how they are truly faceted in ways that
facilitate further nuanced analysis - and not the other way around, where the
systems are a product of an analysis. It's a short-circuiting of the classical
methods of scientific analysis and somewhat defies the limitation of models
that we are so accustomed to.

Instead, they embody an underlying system with dynamic networked coherent
responses. I've thought that there's something fundamentally different about
them and a way to punch through some of the computational, analytical, and
measurement barriers presented by classical analysis on traditional systems.

I've met one person,
[http://ti.arc.nasa.gov/profile/Vytas_SunSpiral/](http://ti.arc.nasa.gov/profile/Vytas_SunSpiral/)
who thought the same way I have with a requisite technical background to see
the implications of this school of thought, and so far, that is all other than
perhaps, Buckminster Fuller in his 1982 book, Synergetics - which deals with
the same concept.

I worked on this a few years and then I put it down, about 12 years ago. I hit
the end of my cognitive ability in the research and haven't returned. It's a
redefinition of analytical engagement. The classical Aristotelian discreteness
is a limiting factor in its development. Stepping outside this while
maintaining a descriptive formality of what constitutes this form of analysis
is exceedingly difficult.

I apologize that this is so vague but it is, for the most part, completely
unexplored. I think there's a very real possibility of coming up with a
divergent philosophy of science with a completely different disciplinary
system - but with higher accuracy and fidelity of analysis and results of some
of the problems which are for intents and purposes, currently intractable due
to the compounding effects of being multi-faceted systemic problems.

Here we are, we can construct highly-coupled, dynamic, reactive, but
ultimately stable systems - the same class of systems we see in our "unformed"
natural world. That's the key insight - that this is a real thing and that
there is a distinct and different way of dealing with it - and that it can be
exploited generally. This I believe, is inherently revolutionary.

If you've read all this and don't think I'm nutso, then congratulations, we
can work together maybe. Just respond below. I think this could honestly be
the most productive and meaningful project that people could ever engage
themselves in.

~~~
FiatLuxDave
I saw Vytas' presentation at the NIAC symposium a few weeks ago, and as
someone whose only previous exposure to tensegrity systems was the typical
outsider's view of its use in architecture and toys, I have to say that his
robots are damn cool. I'll post a link to the video after I get out of the
meeting I have in a few minutes, if no one beats me to it. If you haven't seen
this stuff it's worth seeing just for the cool factor alone.

I agree with you that one of the most difficult things about tensegrity
structures is predicting their behaviour under stress and failure - and since
behaviour under exactly those circumstances is also one of the main strengths
of the concept, that kinda sucks. It's like trying to sell a car which gets
better gas mileage, but you can't really predict how much. Better but
unpredictably better can be a hard sell and especially bad when trying to
optimize a plan for.

I see a lot of parallels between the concept of tensegrity and certain
concepts of resilient design of complex software. In both cases, testing (and
having good test cases) is a vital component of testing. In both cases, even
with testing it is hard to have a good predictive model of failure, because at
a certain level the complexity of test cases can start to compete with the
design itself.

What I see as the really cool thing about what Vytas is doing, is the addition
of controls (e.g. motors etc) to tensegrity structures. This only adds to the
complexity when it comes to testing, because now there are many more
variables. However, if this is a huge issue, it is theoretically possible to
set the controls in such a way that it actually reduces the space of possible
behaviours, and thus makes analysis more tractable. Of course, I think it's
much cooler to go the other way and make the darn things do crazy stuff, but
it all depends upon what you need out of a design. It's somewhat the same
issue with a robotic arm: it can move in so many ways, sometimes the easy or
safest way to do a job is to restrict the possibilities (like not letting it
move into a danger zone). But making it dance is more fun!

~~~
akagogino
I'm working with Vytas at NASA on the control issues for these tensegrity
robots. One of our main ways to address the complexity issue is to use machine
learning to determine control parameters. We have been using traditional
evolutionary techniques as well as some techniques related to importance
sampling. A counterintuitive result of using evolutionary controls is that the
control problem does not necessarily become more difficult as the complexity
of the structure increases. This is because the number of good solutions may
increase faster than the solution space. Currently in hardware, we are
building relatively simple structures, but we hope to expand to more complex
ones in the future.

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TheLoneWolfling
So effectively, the percentage of good solutions increases as the complexity
increases?

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ribs
Every year I've gone to Burning Man I've lived in a tensegrity-supported
structure. See

[http://shelter-systems.com](http://shelter-systems.com)

~~~
kd5bjo
Tensegrity structures don't have any internal bending forces, just tension and
compression. Those tents appear to be based on bent or curved struts exerting
forces in several directions, so I doubt they're actually tensegrity
structures.

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agumonkey
Ha, I was thinking about similar system but non static, absorbing multi-state
ones. Fuels my curiosity back, so thanks.

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Duhveed
love tensegrity! I'm working on a springy tensegrity bar stool.

