Subject:
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Re: THOUGHTS on mapping with Lego Robot ( added to searching walls)
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 28 May 2003 05:21:49 GMT
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Viewed:
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1018 times
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I'm not good at programing at all, but have some thougts about maze-mapping:
If you have some metods of positioning system like GPS then you know exact
where the robot are at all time, then the robot can send information back to
the PC where there are obstacles.
A GPS system with the RCX could be made in diffrent way:
1. A friend of mine had a competition on a course at the university here
where I live where they had a camera high up over the area they where ment
to use. The camerasoftware recognized icons attached to the top of each
robot and could detect direction of the robot and a grid position and sent
this back to the LAN where all computers that controlled the RCX-robots out
on the field.
There was a common IR tower too besides the camera that was connected to the
LAN and every competitor could send commands to their robot through this
IR-tower.
2. You can have markings on the floor with either color or lines or
something that differ from each sector or grid possition on the field. Or a
mix of color lines that is diffrent from each sector. Those sectors have
offcourse to be predefined so the RCX always now where each sector is in the
world.
With a type of "I-know-where-I-am" system (GPS) you can easy map each sector
and see if there is obstacles between sectors.
Just some thoughts....
Regards
Øyvind Steinnes
http://www.brickshelf.com/cgi-bin/gallery.cgi?m=Phoenix
"Steve Baker" <lego-robotics@crynwr.com> wrote in message
news:3ED3F260.2010905@airmail.net...
> Bill Blackmer wrote:
>
> > What I want to do is take a five foot by five foot square, put random • items
> > in the square, MAP THE SQUARE AND OBSTACLES and run our dog robot around • the
> > course and never have it stop. I do not want to do obstacle avoidance • (that
> > is much easier) I want to build a map and work from it.
>
> It's very difficult because all of the 'dead reconing' methods out there • are
> approximate and accumulate errors.
>
> If you drive your robot 10 feet in a straight line, your software will • probably
> by 'off' by maybe a half inch, after 20 feet, you'll be off by an • inch...after
> an hour of driving around, you could be just about anywhere! Turning is
> worse still - if you drive around a zig-zag course for 10 feet, you'll • probably
> be off by many inches in position and tens of degrees in heading.
>
> You need some way for the robot to (at least periodically) do a check on
> some absolute position to reset it's internal position indicator.
>
> > To do this, we have acquired several HiTechnic Sensors (these sensors • are
> > much more accurate then the Lego sensors - Compass, Ultrasonic and • Infrared
> > Range Sensors); and we have created several statistical averaging and
> > correction algorithms, etc.
>
> But things like wheel slip, slop in the gear train, small errors in the
> diameters of wheels, the fact that the Lego rotation sensors sometimes
> gain or lose a 'count' (especially when moving slowly)...all of these
> things conspire to make this a completely intractable problem.
>
> There are things you can do to lessen the problems - but *some* inaccuracy
> is certain to occur and if the "dog" robot doesn't periodically know with
> some precision exactly where it is, the errors will build up with alarming
> speed (ESPECIALLY when the robot turns).
>
> One idea that might work would be to have a 'kennel' for the dog - with
> a funnel-like entrance and an interior that *exactly* fits the shape of
> the robot. If the dog returned to the kennel every so often, the funnel
> would point it into the kennel even if it's navigation was off by a bit
> and the tight fit inside the kennel would allow the robot to reposition
> it's internal navigation coordinates to be EXACTLY where the 'kennel'
> is known to be. There are other ways to achieve the same effect - a
> barcode placed on the floor, navigation lights placed around the arena,
> etc.
>
> ---------------------------- 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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