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 17:00:35 GMT
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Original-From:
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Paul Speed <pspeed@augustschell.com+NoSpam+>
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Viewed:
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575 times
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Hello,
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.
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.
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
>
> #######################################################################
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Message has 4 Replies:
 | | Re: Line Followers
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| Perhaps the light sensor could be placed at the end of a vertical arm that swings in a cone pattern. This would prevent the twisting of connectors. -Wes (...) (25 years ago, 16-Nov-99, to lugnet.robotics)
| | | Re: Line Followers
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| (...) That is the method I've usually assumed would be best. (...) 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. My two cents: 1) maybe a (...) (25 years ago, 16-Nov-99, to lugnet.robotics)
| | | Re: Line Followers
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| (...) Just a thought (and the reason I still want to use real walls): by bumping into a wall, there are small orientation errors that are introduced (especially when hitting it at an angle). I just like tougher problems! :-) /Vlad (25 years ago, 16-Nov-99, to lugnet.robotics)
| | | Re: Line Followers
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| You could make a gantry that can make the arm go forwards and back, and at the same time have it on another gantry that can move side to side. Move both gantrys (sp?) at once and you should be able to carve out a rough circle without twistind the (...) (25 years ago, 16-Nov-99, to lugnet.robotics)
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Message is in Reply To:
| | Re: Line Followers
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| 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 (...) (25 years ago, 16-Nov-99, to lugnet.robotics)
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