Subject:
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Re: Lego or Biscuit pc/Linux (for path following robot)
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 6 Mar 2003 15:02:48 GMT
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Original-From:
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Steve Baker <SJBAKER1@AIRMAIL.NETantispam>
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Viewed:
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782 times
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Teoman Naskali wrote:
> I have to build a robot for my thesis projet that will be able to follow a
> line and inetrpret some graphical commands on the line (like left triangle
> turn left, big circle wait 10 secs etc)
> Then i saw lego mindstorms, and started wondering IS IT SERIOUS ENOUGH? Does
> it have the power on its own to accomplish such a task?
Well - if you want to see a 'graphic' of (say) a circle and intend that to tell
the robot to go around in a circle, you'll need a camera. The RCX isn't powerful
enough to interface to a camera (although some dubious Lego adverts seem to
indicate otherwise!). You can interface to the Lego camera only via a long cable
going back to the PC.
HOWEVER, apart from the task of recognising those icons, it's all very easy.
Robots that can follow a line are REALLY easy to build with just a simple
light sensor - I bet nearly everyone on this mailing list has built at least one.
Could your "graphical commands" be bar-codes?
I have built robots that could read a bar code whilst following a black line.
You can either place the bar codes a couple of inches away from a reasonably
straight section of the line you are following and use a second light sensor
to read them - or (as I have managed) - embed a black-on-grey barcode in a grey
line. The robot is programmed to follow either grey or black - and can use the
black-on-grey image to extract a few dozen bits of binary information.
Using Lego for this is absolutely the right way to go. It saves you all the
tedious mechanical engineering that goes with building a robot. It also gets
you out of all the nasty issues of interfacing simple switches and motors to
a PC or whatever. Even if you have to use a PC to provide the image processing,
the savings in time and money will be significant. I don't think you could do
this with a modified RC Car for example.
> Or can it be teleguided by a computer (robot sends images to the computer
> which processes the images and controls the robot) (If possible the computer
> can be dragged on wheels...)
The Mindstorms system comes with an infra-red link to allow your PC to
communicate with the robot's computer.
However, if there *must* be a camera on the robot then the best solution
I know of is as follows:
1) Go to www.thinkgeek.com - they have some little radio controlled tanks that
can carry a camera. That camera broadcasts it's image as a signal that a
standard NTSC television can pick up.
2) Buy a TV card for your PC. It can now capture the image from the thinkgeek
camera - and presumably do the image processing to extract your 'graphical
commands'.
3) The Lego Mindstorms robot can carry the camera around and obey commands sent
to it from the PC via the Lego Infrared system. If it gets no special commands,
it just mindlessly follows the line around using it's light sensor.
Tadaaa!
However, if you can bend the rules to allow the 'graphical commands' to be bar codes,
you can make a truly autonomous robot to do the task out of an absolutely standard
Lego Mindstorms set.
> Besides how far can I use legos? Can i use them in my further studies,
> like can 2 cameras be attached and effectively controlled so the robot is
> aware of its 3D environnement. Can i do AI stuff on it?
The Lego computer is fairly limited - it doesn't have a lot of memory and it's
interfaces to the world don't extend to cameras and such. Using the standard
Lego "operating system" in that computer limits you to programs of a few
hundred to maybe a couple of thousand lines. However, you can replace that
firmware with a freeware Operating System called 'BrickOS' - which allows you
to write much larger programs that run much faster. Whether it can do "AI stuff"
depends a lot on what you mean by that term.
I don't think it can be "aware of it's 3D environment".
> I could buy a biscuit pc aswdell ( small pc 800mhz via cpu, everything
> onboard, 10cm x 8cm) which would do me more good for learning AI and image
> processing for robotics. Please advise, i have to make a decision and start
> my project which is due in 2 and a half months.
Well, you could carry a small PC around - if it has a USB or serial port, it
could communicate with the Lego robot (which you'd still need because it
has all the interfaces for reading light sensors, driving motors, etc, etc).
I don't know whether those tiny PC's can interface to cameras or not.
But if your project allows you to use bar codes instead of little pictures
of triangles and circles, it'll be a million times easier and can be done
with off-the-shelf Lego parts. If humans need to see the 'graphical
commands', couldn't they be printed next to the bar code? The trouble with
course projects is that they tend to set up artificially difficult problems
that force you to look into things like image processing - where in the
real world there is a MUCH more practical solution that can be done with
relatively low tech parts.
If you needed a machine like this in a factory (and you could easily
imagine how that would be useful). You wouldn't even consider using
image processing. A bar-code (or metal studs embedded under the
track or something) would be much more practical.
It would be pretty neat to have a robot drive around a track - and
stop to pick something up when it sees one barcode - then continue
to drive along the track until it sees another barcode to tell it
to put the object back down again.
I played a bit with that in my long quest to build the
"Fetch-me-a-beer-o-bot". :-)
> I would be glad if you send me any ideas on my project.
No problem. Let us know how you get on!
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://www.sjbaker.org
Projects : http://plib.sf.net http://tuxaqfh.sf.net
http://tuxkart.sf.net http://prettypoly.sf.net
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Message has 2 Replies:
 | | Re: Lego or Biscuit pc/Linux (for path following robot)
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| (...) >> (like left triangle turn left, big circle wait 10 secs etc) (...) Steve, for the most part I agree with you. However, I was thinking that a robot with two or three light sensors should be able to accomplish this task. See the following (...) (22 years ago, 6-Mar-03, to lugnet.robotics)
| | | Re: Lego or Biscuit pc/Linux (for path following robot)
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| (...) This has been done. I remember seeing a video clip of a Mindstorms robot doing just this. The builders had it on display at some sort of convention (I think). The robot followed a line that made a loop, at certain places, there were different (...) (22 years ago, 7-Mar-03, to lugnet.robotics)
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