Subject:
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Re: Navigation using landmarks (Was: Re: lasers and RCX)
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 14 Jun 2002 22:56:24 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail.netNOMORESPAM>
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Reply-To:
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SJBAKER1@nospamAIRMAIL.NET
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Viewed:
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853 times
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Mauro Vianna wrote:
> The funny part is that my alternative nav system was very similar to yours.
> But it was based on a line, not a ? shape.
> Since I never really tried it in a large scale I don't have real results to
> show. But I pretend to try it again.
I looked into several patterns. What would be ideal would be something which
you could drive across along any straightline path and get back your direction
and position from the pattern of dark and light.
It seems rather unlikely that such a pattern could exist - but I havn't
finished thinking about it yet.
Meantime, I settled for a pattern that could be approached from any direction
and then *followed* to lead you to a barcode that would tell you what you need
to know.
> The main idea was to use a robot with rotation sensors on 2 wheels. Starting
> from a known position it would be able to turn and move with some precision.
> But there will still have some acumulated error due to slippery, obstacle
> avoidance, etc.. But it would be enough to move from one landmark to the
> other.
> Once there, it needs to move to a known position and direction. A bar code
> would be used as the landmark id. Coords would be hardcoded or stored by a
> landmark search routine.
Yes - my plan exactly.
> I liked your idea of a ? shaped. It is a big target, no matter which angle
> the robot approaches. In my case the robot had to search the line once it
> detected it was over a white sheet of paper (it was lighter than my lliving
> room floor).
Yes.
> The problem with the tail you mentioned may be solved using grey for the
> line and black for the bar code. I never tried it...
No, me either.
> In my experiments I had trouble to have a precise direction. The
> line-following algoritm I used was the one that follow the border of the
> line. But once the line ends the direction wasn't precise since it still
> tried to correct before detecting the line was over. Maybe using a black dot
> in the end solves the problem, like it was used in Dave Baum book.
Well, the idea is that there could be a straight section of line before the
barcode. Following that *should* allow the machine time to get nicely
aligned so it can just drive forwards and still hit the barcode.
What would make this easier would be if you had TWO light sensors - one to
follow a line - and another to read off information. Then, you could just
have a circle (to follow in a clockwise direction with a light sensor to
the left side of your robot...and inside that circle, printed in a ring
inside it, there could be a series of bar codes that would tell you your
present heading. The robot could drive in a circle tracking the line -
and just go off in a straight line once it had read off the heading it's
looking for.
> I had one idea for correcting the direction but I never tried it. It would
> be a mechanical solution. Something like a "docking station" (built with
> lego?). It should be funnel shaped so that if the robot aproaches from a
> aproximate correct angle, it would fit straight in the docking station and
> correct its direction.
Yes - that could certainly work.
----------------------------- Steve Baker -------------------------------
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URLs : http://www.sjbaker.org
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Message has 1 Reply:
Message is in Reply To:
 | | Re: Navigation using landmarks (Was: Re: lasers and RCX)
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| Hi, Steve I thought about most of your solutions (sphere, bycicle and 3 mirrors). Unfortunatelly I came to the same conclusions. The funny part is that my alternative nav system was very similar to yours. But it was based on a line, not a ? shape. (...) (22 years ago, 14-Jun-02, to lugnet.robotics)
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