Subject:
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Re: Line Followers
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 16 Nov 1999 18:27:09 GMT
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Original-From:
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Paul Speed <pspeed@augustschell+saynotospam+.com>
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Viewed:
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423 times
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Luis Villa wrote:
>
> On Tue, 16 Nov 1999, Paul Speed wrote:
> > After various discussions here about maze walkers and synchro
> > 'bots, I decided to try my hand at YASB (yet another synchro 'bot).
> > Furthermore, I decided that instead inverting the problem as Ralph
> > did, that I would turn it inside out by having a solid black line that
> > traces the path of the maze instead of having walls.
>
> That is the method I've usually assumed would be best.
>
> > This means that I will need an efficient way of tracking the
> > line and detecting junctions. Initially I will leave the maze
> > "square", but I hope to be able to generalize in the future.
> >
> > My idea is to simulate having multiple light sensors by
> > using one light sensor to sample in several places. Imagine a light
> > sensor moving around in a circle sampling discrete points along this
> > circle. Standard methods have been discussed for various forms of
> > rotation sensors but I think a "touch sensor pressed by a gear"
> > type has some elegance when considering that the touch sensor could
> > probably be stacked on the same port with the light sensor.
>
> Wow. This sounds like a mechanical mess, but an elegant solution (in a
> broader sense) to the depth/breadth issue I was talking about last night.
> Good luck.
re: Mechanical mess - agreed. :) Hopefully, and elegant
solution will present itself there too.
>
> 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.
> 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.
-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
> > > >
> > > >
> > >
> > > #######################################################################
> > >
> > > Profanity is the one language that all programmers understand.
> > > -Anonymous
> > >
> > > #######################################################################
> >
> >
>
> #######################################################################
>
> Profanity is the one language that all programmers understand.
> -Anonymous
>
> #######################################################################
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Message has 2 Replies:
 | | Re: Line Followers
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| (...) Hmm. If you only blip at the compass points, what happens if you "cross" a fork while between one of the four points? (...) Ahh. I missed the synchro part. Crazy. :) -Luis (...) ###...### Profanity is the one language that all programmers (...) (25 years ago, 16-Nov-99, to lugnet.robotics)
| | | Re: Line Followers
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| Sorry! I misunderstood you in that last post. If you want to make it go all the way around the robot (which is how I understand it now), then all you have to do is put the light sensor + arm on a turntable and rotate that. To keep from getting the (...) (25 years ago, 16-Nov-99, to lugnet.robotics)
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