
World's Fastest Rubik's Cube Solving Robot [video] - prawn
https://www.youtube.com/watch?v=ixTddQQ2Hs4
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Gravityloss
More like a machine, not a robot. One of the traditionally viewed differences
between industrial machine automation and robot automation is that robots are
relatively general and can be repurposed.

Think of wiring vs software.

I would think a real robot solving a cube would perhaps at least have to pick
it up and put it back down after solving.

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erikpukinskis
> robots are relatively general and can be repurposed.

I see your point, but I'm not sure that's a good definition. It's a _very_
fuzzy line. Is a Roomba a robot? It's not a general purpose device.

I've always found it difficult to define intelligence in any useful way, but
when I think about it I usually come to the conclusion that it's almost
indistinguishable from adaptation, which is easier to define. And adaptation
is sort of an interesting line to use for the machine/robot distinction.
Machines do work, but robots adapt?

By that definition the Roomba is a robot... it will adapt to foreign objects
you place in front of it. This Rubiks machine can adapt to different
configurations. But there is a small finite space of scenarios it can adapt
to.

So maybe that's it. How many states can you adapt to? If not very many, you're
a machine. If quite a lot, you're a robot!

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Flammy
Fun fact: Every possible cube starting pattern can be solved in 20 face moves
and a maximum of 26 quarter turns.

[https://en.wikipedia.org/wiki/Optimal_solutions_for_Rubik%27...](https://en.wikipedia.org/wiki/Optimal_solutions_for_Rubik%27s_Cube)

EDIT: Details, history, and math of proof here:

[http://www.cube20.org/qtm/](http://www.cube20.org/qtm/)

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DrScump
Why is it always solved in the _same final orientation?_ (red to near left,
blue to near right, ...)

It would seem to me that from a truly random start point to the truly fewest-
moves solution, the colors would end up facing random orientations for each
run.

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Flockster
Because within the cube, the centerpieces are fixed to a core. And because
these define the orientation of the cube and are fixed within the robot you
end up having the same orientation every time. This happens with every solving
robot that only turns the outer layers of the cube, meaning the inner layers
and therefore the centerpieces do not move.

~~~
gohrt
It's mathematically interesting that the optimal solutions (I assume that the
robot uses the fewest-moves-possible to get its high-speed results) never
require rotating the middle layers.

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sebastos
On closer look it's actually trivial. Any move that requires rotating a middle
layer is isomorphic to rotating the top and bottom layers in the other
direction. :)

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ng-user
I remember seeing this a couple days ago and they said they had tried not to
modify the cube but weren't able to get the right amount of leverage needed to
rotate it and thus insisted on drilling into each center piece. Don't think it
still counts, pretty cool set up none the less.

~~~
kafkaesk
The creators themselves are apparently rather confident that it will indeed
count, at least for the guiness record. The World Cube Association doesn't
have a "robot category" as far as I am aware.

[https://www.reddit.com/r/Cubers/comments/42ank6/worlds_faste...](https://www.reddit.com/r/Cubers/comments/42ank6/worlds_fastest_rubiks_robot_11_seconds_official/cz98r8n)

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hamitron
its really awesome what they accomplished, but does the drilling diminish the
achievement?

~~~
trevyn
Yes! ;)

I wonder if suction cups under high vacuum could work.

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Someone
They might work, but if, as I do not rule out, the machine uses dead reckoning
(i.e. it doesn't use its cameras to detect when a face is oriented at exactly
90 degrees, but just rotates a face by what it knows to be 90 or 180 degrees),
I think it would be difficult to properly set up the machine.

You would have to place the suction cups exactly at the center of each face,
cannot allow one cup to suck a bit harder than another, and have to make sure
all faces are very close to being perfectly flat in the starting position.

Edit: also, if those suction cups slip, I guess you will be looking at more
Rubik's cube parts than you thought existed.

~~~
vectorjohn
I don't think you need all that. They use stepper motors so they do indeed
turn exactly 90 degrees. What they _would_ have to worry about is the suction
cup not sticking perfectly. E.g. after a 90 degree turn if the momentum makes
that part of the cube slide a little when they try to stop, it will introduce
a small error. Maybe turning other parts of the cube would correct it.

~~~
JoshTriplett
I've seen other Rubik's cube solvers that handle this by heavily lubricating
the cube, so that if the machine attempts to turn it without perfect
alignment, it'll just slip into alignment rather than snapping.

See
[https://www.youtube.com/watch?v=X0pFZG7j5cE](https://www.youtube.com/watch?v=X0pFZG7j5cE)
for an example solver.

~~~
gohrt
Human solvers do the same.

~~~
Someone
Human solvers do not hold all six sides of their cube in a tight grip.

I guess it all depends on how much force it takes to turn such a stepper motor
when it isn't powered.

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udev
This is one of those cases that neatly separates the (ivory-tower) academic
types from the (getting-hands-dirty) engineer types of people.

People who say that drilling the wholes in the cube diminishes the
achievement, the perfect-or-nothing crowd, belong to the first group.

People who see the drilling of holes as a valid tradeoff to achieve higher
performance are more pragmatic and belong to the second group.

~~~
cjfont
This doesn't seem to be a question of pragmatism -- they're going for a world
record, not trying to solve a practical problem. I'm no expert on this, but it
seems to me like the criteria for obtaining a world record title would include
not modifying the object used. To me this is like trying to beat the record
for furthest soccer ball kick by modifying the materials used in the soccer
ball.

~~~
Tepix
Agreed. The holes invalidate their record attempt. It's like drilling channels
into a football so you can throw it farther.

~~~
waynecochran
Or deflating a ball to beat the Colts...

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udev
How about lubricating the cube so that it rotates faster? Lots of people do
that. Would that count as a modification?

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chbrown
After frustratedly fixing an unsolvable Rubik's cube over Christmas break (my
dad thought it'd be funny to "solve" it by peeling off the labels and putting
them back on, but got tired halfway through and left it in an unsolvable
configuration), I'd love to see what their robot does if you give it an
unsolvable cube.

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Levex
It would most likely not do anything at all. As the Rubik's solving algorithm
should return null (if not stuck in an infinite loop).

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uxcn
How are times compared for rubik's cube bots? I would guess there's some
variance even for the same bot solving the same cube from the same state.

It might be interesting to see a competition based on number of moves.

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tetraodonpuffer
what would be interesting is if there was a category where the robot solver
has to grab the cube from the table, analyze it, solve it, and put it back on
the table in the same spot, would be cool to see the compromises that would
have to be made for speed of transfer/analysis vs speed of solving

~~~
lutusp
Yes, true, but consider the fact that, at the moment, the best robots in the
world still can't fold a towel without enormous effort.

[http://www.npr.org/sections/money/2015/05/19/407736307/robot...](http://www.npr.org/sections/money/2015/05/19/407736307/robots-
are-really-bad-at-folding-towels)

My point is that the intelligence required to pick up the cube and manipulate
it, might require more processing power than solving it when attached to a
frame.

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apalmer
Yeah but that's why it would be interesting. Solving a rubics cube quickly is
interesting from a human standpoint, for a purpose built machine not so
much.... I mean its doubtful that the majority of the competitors wrote the
software algorithm to solve the cube... What they bring is the mechanics
behind it... But really if the professional robotics orgs got involved they
would probably just outclass the record holders... Thing is that they arent
even interested because their is No money in it and its just not that
interesting a robotics challenge

