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 19:54:20 GMT
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Original-From:
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Steve Hassenplug <SteveH@mailcode.com>
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Viewed:
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565 times
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I've been working on a line following bot. My original idea was to have an
arm that swings back and forth (to cover about 3 inches) over a line and
would be able to adjust the direction of the bot based on the position of
the line within the arc.
The first problem is that running a rotation sensor directly off the arm
doesn't give me much in the line of feedback (only three of four counts)
and I couldn't get touch sensors to work very reliably, either. So it was
hard to track the position of the arm.
The next issue is that there is a problem if, for example, the arm swings to
the left at the same time the line swings to the right. The bot could loose
the line altogether.
So, I stepped back and made a very simple edge following robot. It turns
right when it sees black, and left when it sees white. It still seems to
wiggle too much, but I'll work on that. It's really my first line following
bot. It made it around the [old] test track in less than five seconds, but
I'm not sure how that compares to other bots.
Does anyone have suggestions on how to build a track everyone could use?
Some way for us all to compare against each other?
My first thought is to make up a 'track' that consists of several pieces of
paper that can be taped together to form a single track, and then post these
pages on the web. Any other ideas?
Steve
-----Original Message-----
From: Paul Speed [mailto:pspeed@augustschell.com]
Sent: Tuesday, November 16, 1999 1:27 PM
To: lego-robotics@crynwr.com
Subject: Re: Line Followers
Luis Villa wrote:
>
> > 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
> > > >
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Message has 1 Reply:
 | | Re: Line Followers
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| Steve Hassenplug wrote: <snip> (...) Full details for building a suitable track based on a FLL design can be found if you go to the NJRC website at (URL) click on the playing field icon. Happy building! -- C S Soh (URL) where air is power (25 years ago, 18-Nov-99, to lugnet.robotics)
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