Subject:
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Re: Positioning
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Newsgroups:
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lugnet.robotics
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Date:
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Sat, 29 Jan 2000 19:46:21 GMT
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Viewed:
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4274 times
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Hi Mauro,
Maybe I'm misunderstanding, but it seems to me that if you can't tell your
robot how to turn correctly, no mapping system would work.
The system I used contained a simple TURN LEFT, TURN RIGHT method. Each turn
is 45 degrees. I didn't really have any problems with this.
David Leeper (may have missed your point)
In lugnet.robotics, Mauro Vianna writes:
> I have been watching this discussion with great interest. I was looking for
> a solution for this problem since I wanted to program a robot to find his
> way inside my apartment.
> The problem I found in the landmark system was that you don't have a precise
> way to tell the robot how much to turn when it find it. Since this error is
> cumulative it will evetually lose the landmarks. It will find the first, the
> second but will eventually miss. It is especially important when the the
> robot moves through different knids of terrain (carpet, plain).
>
> Did anybody try any kind of course correction? I thought about one but
> didn't try it yet. The landmarks could have short lines of different color
> extending from it in the direction of the next landmark. This way an
> algoritm similar to the line folowing could be used to set the robot
> direction.
>
> Ok, ok, the problem of landmarks on the living room vs. wifes persists... :)
>
> Mauro Vianna
>
> "David Leeper" <david_leeper@hotmail.com> wrote in message
> news:Fp0v94.1r1@lugnet.com...
> > Hi Pete,
> >
> > I agree that the short sight is a problem. In my tests, I used wide • strips.
> > Three times as wide as the RCX. And they were no more than a foot apart. • So
> > missing them would have been difficult.
> >
> > In real life, you could use similar tricks. For example, suppose you • wanted
> > your robot to travel from the bedroom, into the living room, go over to • the
> > corner and turn on the stereo. You could put a red rug in front of the • stereo.
> > That's your landmark. People visiting you wouldn't think you're strange • (like
> > they would if you layed colored strips of paper all over your house) and • the
> > robot would have a (say) 1 foot by 3 foot target to hit.
> >
> > You could also combine the mapping methods. Since the relationship of your
> > bedroom to your living room is unlikely to change, you could use a timing • map
> > to navigate that. Then use a landmark map to zero in on the stereo. If • your
> > girlfriend moves the stereo a few feet to make room for her plants, your • robot
> > still finds the stereo.
> >
> > And, of course, I'm hoping sonar will increase the range that landmarks • can be
> > spotted. I'm not expecting it to be easy, and I don't even know what a
> > landmark would look like to sonar, but I'll find out more this summer.
> >
> > And in talking about all this, it's starting to dawn on me that error • handling
> > while traveling a map is relatively unexplored territory.
> >
> > David Leeper (is still learning)
> >
> >
> > In lugnet.robotics, Pete Hardie <pete.hardie@dvsg.sciatl.com> writes:
> > > David Leeper wrote:
> > > >
> > > > Hi Pete,
> > > >
> > > > I was looking back over you post and realized I didn't answer a couple • of
> > your
> > > > questions.
> > > >
> > > > > what are the steps leading up to "...when you get to the X..."?
> > > >
> > > > In the program I wrote there are only a few commands. Go forward. Turn • left
> > at
> > > > landmark X. Turn right at landmark X.
> > > >
> > > > > And how does
> > > > > a bot determine that it has not found a landmark and needs to ask more
> > > > > directions.
> > > >
> > > > To be honest, I ignored the problem. Although I knew it could happen in
> > > > theory, in practice it never did, though I admit it was a limited set • of
> > > > trials in a static environment. Offhand, I can think of a couple of • possible
> > > > solutions. 1) Just stop moving after a given time limit or wheel • rotation
> > > > count. 2) Have a set of landmarks that tell you when your lost, as in • "If
> > you
> > > > see a McDonalds on your left, you've gone too far." Really, both • answers are
> > > > the same. Have a mapping system to tell you when you're not correctly
> > > > following your mapping system.
> > > >
> > > > Again, I think the major flaw in all mapping systems that I've seen is
> > > > the "GO" command. Moving a robot is not acurate and the programmer has • to
> > come
> > > > up with ways to deal with the inacuracy, whether its a timer system, a
> > > > rotation system, or landmark system.
> > >
> > > The main problem I'm seeing is that the legobot has very short sight, and • so
> > it
> > > can
> > > only travel a certain distance before it is nearly sure to miss a • landmark,
> > and
> > > then
> > > be lost.
> > >
> > > Also, in the Real World (tm), creatures with the limited senses of • legobots
> > tend
> > > to
> > > use trail-following methods (ants and scent trails, etc) as the main path
> > > tracking,
> > > and perhaps landmarks to ID branching points. Creatures with long-range • senses
> > > use distance measures (bees and the honey-dance)
> > >
> > > --
> > > Pete Hardie | Goalie, DVSG Dart Team
> > > Scientific Atlanta |
> > > Digital Video Services Group |
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Message has 2 Replies:
 | | Re: Positioning
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| Well, it seems that you all want this to be flexible. How I understand it is that you will have to do at least some preperation to use this landmark system. Now I was thinking about Marco's idea-put a grid of IR beams on the floor, and use the (...) (27 years ago, 30-Jan-00, to lugnet.robotics)
| | | Re: Positioning
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| Well, I can tell the robot to turn 45 degrees using timing but it's not precise enough. It would be something about 43-47 degrees. I could use a rotation sensor (but I don't have one) to increase accuracy but there will always be a smal error. After (...) (27 years ago, 30-Jan-00, to lugnet.robotics)
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Message is in Reply To:
| | Re: Positioning
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| I have been watching this discussion with great interest. I was looking for a solution for this problem since I wanted to program a robot to find his way inside my apartment. The problem I found in the landmark system was that you don't have a (...) (27 years ago, 29-Jan-00, to lugnet.robotics)
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