Subject:
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Re: challenge: LEGO copier
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 5 Aug 2004 22:05:27 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail.[StopSpam]net>
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Viewed:
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1282 times
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Joe Strout wrote:
> > Also, it's going to be hard for any type of sensor (light sensor or camera)
> > to tell the difference between a brick of unknown color, and the background,
> > unless you have stereo vision (two cameras).
No - you'd just use a touch sensor that you could lower down onto the model
you are 'scanning' - it would be easy enough to measure whether there was a
hole or a brick.
> We've been assuming a limited set of colors -- say red, white, and blue.
> Put this against a black background and it'll be quite easy to parse it
> with a camera. (I don't know much about LEGO robotics, but I used to
> work in machine vision, so I can say this with confidence.)
The Lego camera isn't really much use because it can't talk to the RCX.
Hence you have to have a PC connected to both the camera and the robot.
It would be possible to distinguish three colours with a simple light
sensor.
I don't think the 'scanner' part is hard at all...having seen the Lego
photocopier - I believe we could build a scanner - even if there are
a few different colours of brick and holes in the design.
That's something you could do with a single RCX - and I think most
people who've had a little building experience would be able to
tackle it with a good deal of confidence. Then it would be easy
to have the 'scanner' RCX send the list of colours and locations
via IR to the 'constructor' side of things.
The 'constructor' side is a different matter though - I think it's
a VERY tough problem just to build a robot that can build a solid,
straight line wall out of one kind of brick. Picking up the
bricks from some kind of feed 'hopper' - aligning them to the bricks
already in the wall accurately enough and applying enough force to
connect them are all very tough problems.
Having it have to deal with bricks of different colours makes it
MUCH harder - because you need multiple 'hoppers' containing bricks
of different colours - so the 'picking them up' problem gets much
more difficult.
Making it have to use different sizes of bricks makes it unbelievably
harder. You'd need MANY more hoppers - different sized hoppers. Then
the gripper to pick up the brick and place it would be nightmareish -
and the force you need to apply to snap together larger bricks starts
to be comparable to the strength of the robot itself (which is made of
Lego remember!) - and making the 'gripper' both strong enough to do
that *and* small enough to deal with 1x1's *and* light enough to reach
across a large distance - yet subtle enough not to destroy a thin column
of bricks by squeezing them too hard...all of those spell disaster to me.
Then, finally having to construct things like the letter 'M' example
(things with arbitary gaps and holes) in an arbitarily complex order
makes it almost impossible.
Blindfold yourself, tie one hand behind your back and try to make the
letter 'M'. A human hand is by far the most dexterous device in existance,
and even when driven by the incredibly powerful human brain, this is almost
impossible.
I VERY much doubt we'll see anyone even attempt this problem...which makes
it rather futile to think too deeply about it.
I think a better (and frankly, more interesting) problem is to build
an arbitary 3D sculpture from *only* (say) 2x4 bricks and using three
different colours. This would be more impressive to watch (IMHO) and
more possible to do.
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://www.sjbaker.org
Projects : http://plib.sf.net http://tuxaqfh.sf.net
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Message has 1 Reply:
 | | Re: challenge: LEGO copier
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| (...) One could cheat (if you consider it that) on this pretty easily, though. Instead of hoppers containing a jumble of bricks, each feedstock source could be a neat queue of bricks in a constant orientation. Grabbing the next brick from such a (...) (20 years ago, 6-Aug-04, to lugnet.robotics)
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Message is in Reply To:
| | Re: challenge: LEGO copier
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| (...) Why would that be impossible? You'd start by building up the sides; when you've done row B, then you can attach the block in row C, followed by the one in row D. So yes, this means the robot has to be able to move back and forth; it can't just (...) (20 years ago, 5-Aug-04, to lugnet.robotics)
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