Subject:
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Re: Autonomous Robot
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 9 Aug 2000 23:14:21 GMT
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Viewed:
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547 times
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in article 4.2.0.58.20000809145637.00c0a460@mailserver, John Barnes at
lego-robotics@crynwr.com wrote on 8/9/00 3:07 PM:
> I think that this autonomous robot thread has been the most interesting
> one on lugnet for a while.
>
> I am fascinated by all the creativity which pours out in response to this most
> interesting challenge.
I'm enjoying it too. I hope my employer isn't reading this group! :) If
so, Hi John, I'll have that server done right away, working on it now.
>
> Personally, I have cheated this issue by using ultrasonics, but that isn't
> to say
> I'm not interested in the problem as laid out.
>
> I have a suggestion, which I think may date back 50 years to the early days of
> radio direction finding. I believe the British Isles are (were) surrounded
> by a system
> of transmitters with counter-rotating antennas, one rpm. Each had a different
> signal, so you listened and counted the time for each signal and deduced your
> resulting bearing from the transmitter.
>
> Can't you do this with two counter-rotating lasers! The RCX sits out there and
> counts out the time between three hits, 1 - 2 - 1 for example. The relative
> time
> gives the angle. There is an ambiguity but if the transmitter is in the
> corner of the
> room, then the ambigous position is not real.
Wow, this is another good idea! This gives you your bearing with a single
base station and one light sensor.
It will be pretty hard to guarantee a specific rotation rate with Lego
pieces, so you'll probably need to measure it with an angle sensor and
broadcast the time information via IR. If you broadcast it continuously,
the robot will have a stored copy of it from the last time it was within
range of the base station, which should be pretty close to correct assuming
the robot hasn't been out of range long enough for the batteries in the base
station to run down.
>
> A crude approach at range, is then to move at right angles to the beam some
> known
> small distance using odometry which should be good for a short straight
> line and then
> resample the transmitter's new angle. You now have all the info to solve
> for the range.
How do you know you're moving at right angles to the beam? Boats have
compasses, so they know their heading. Our robots generally don't know for
sure.
If you can measure the time it takes for the laser to traverse the sensor
accurately enough, as discussed in one of my earlier posts, you can also
figure out your range.
>
> I have no idea if it can be made to work, I haven't tried it.
>
> Also, I wonder if you need lasers or if a pair of counter-rotating
> mini-maglites whould do it!
> They'd be a lot cheaper for testing out the idea.
Laser pointers are not much more expensive than MagLites in my area.
MagLites would have wider beams, which would make determining the time
between beams more difficult to pin down. The width of the beam grows with
distance from the base station, too.
However, the relative brightness of the beam drops with distance from the
base station, which would give you (probably a very rough estimate of) the
range. Lasers don't do that, at least not at the distances found inside the
average dwelling.
>
> JB
>
>
--
Doug Weathers, http://www.rdrop.com/~dougw
Portland, Oregon, USA
Don't spam me - I know how to use http://www.spamcop.net
"On a clear disk you can seek forever"
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Message is in Reply To:
 | | Re: Autonomous Robot
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| I think that this autonomous robot thread has been the most interesting one on lugnet for a while. I am fascinated by all the creativity which pours out in response to this most interesting challenge. Personally, I have cheated this issue by using (...) (24 years ago, 9-Aug-00, to lugnet.robotics)
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