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Subject: 
Re: Line Followers
Newsgroups: 
lugnet.robotics
Date: 
Tue, 16 Nov 1999 19:23:41 GMT
Viewed: 
537 times
  
On Tue, 16 Nov 1999, Paul Speed wrote:
My two cents:
1) maybe a half or 3/4 circle would be all that is needed? No
twisting problems then.

        True, but I sort of like the idea behind having a sort of
blip at four compass points.  It makes maze navigation a simple
problem and then I can focus on maze traversal.

Hmm. If you only blip at the compass points, what happens if you "cross"
a fork while between one of the four points?

2) When you rotate the bot, any idea on how you will realign the
sensor to the bot's new direction?

        That was the idea behind the synchro platform.  The bot will
always be "facing" the same way which is one of the things that
necessitates a full circle sampling.  Initially I will focus on
movement restricted to 90 degrees.  Eventually it would be nice to
develop a more general solution that can handle more than four
directions.

Ahh. I missed the synchro part. Crazy. :)
-Luis

        -Paul (pspeed@progeeks.com, http://www.progeeks.com/)


Just some thoughts-
Luis

      I will leave solutions to the problem of keeping the light
sensor cable from getting twisted as an exercize for the reader.
(heh)  At least until I've built a working example.  Speculation is
always so much easier than proving that it will work. :)

      -Paul (pspeed@progeeks.com, http://www.progeeks.com/)

Luis Villa wrote:

With just one light sensor, the problem is that you have to guess
which direction you just fell off the line. i.e., your sensor
suddently goes from dark to light. Is the dark to your left? Your
right? There's no real way of telling, is there?

If you guess well, you can follow the line well. If you don't guess
well, you are in trouble. Frankly, I have no strategies for
guessing well. However, "go x left, 2x right, 3x left, 4x right" is
not unreasonable, and I believe some variation on that (perhaps x
left, 2x right, 4x left, 8x right, but I'm not sure) is
mathematically provable to be the best solution for this type of
problem. Note: these are not actually go left, but spin left, spint
right, etc. with the assumption that you have stopped when you "lost"
the line.

With two light sensors, this suddenly becomes much easier, and with
three, you can build a great light sensor. However, forks still
aren't dealt with well- you need depth as well as breadth to be able
to analyze those robustly and on the fly (in my opinion). Anyone
have any thoughts on that one?
-Luis

On Tue, 16 Nov 1999, David Morgan wrote:

Date: Tue, 16 Nov 1999 00:08:59 GMT
From: David Morgan <lego-robotics@crynwr.com>
To: lugnet.robotics@lugnet.com
Subject: Line Followers

Hi,

Could someone please give me a little bit of advice on building a line
follower with the standard lego light sensor? I will be doing the
programming  for it with LegOS.

Can you achieve decent performance with just one light sensor?

Thanks!!
     Dave Morgan



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Message is in Reply To:
  Re: Line Followers
 
(...) re: Mechanical mess - agreed. :) Hopefully, and elegant solution will present itself there too. (...) True, but I sort of like the idea behind having a sort of blip at four compass points. It makes maze navigation a simple problem and then I (...) (25 years ago, 16-Nov-99, to lugnet.robotics)

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