Subject:
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Soda-can challenge: beacons, tethers, etc. (was Re: Locating your position with the help of fixed be
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 2 Aug 1999 19:43:34 GMT
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Viewed:
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873 times
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Yet another comment about my "beacon" ideas.
Yesterday I talked with someone who was involved in Joel Shafer's "soda can
challenge" that was proposed in this message:
http://www.lugnet.com/robotics/?n=3968
and learned that the primary reason people are trying to locate their
*position* is only because they need to *return to the start position*. That's
a totally different and much simpler problem.
My "beacon" design as I described it is very slow to use. I talk about rotating
one degree at a time and waiting for one beacon sweep on each rotation; even if
you went 10 or 20 degrees at a time it's still going to take at least 2 or 3
minutes to complete a position reading.
If all you want to do is return to the "home base" for a project like the soda
can challenge, all you need for a beacon is a simple blinking light (that
blinks very fast). For example, just drive the axle of the polarity switch
directly off a motor and run a light through the switch so the light blinks
quickly. The quicker the better.
Since the soda can challenge requires the robot to "enter [the] room", that
means the beacon must be part of the robot. The robot would drop the beacon
(that is, break into two pieces and leave part of itself behind) upon "entering
the room". Fortunately the challenge says to "return to the starting point" and
doesn't require "leaving the room in one piece".
If the beacon blinks fast enough, your robot can scan for the beacon while it's
rotating. Stop rotating when the pulse brightness (measured via the decayed
average technique I described) is highest. Then move forward a bit, and scan
again for mid-course correction.
There are other even simpler ways to return to home base for the soda can
challenge. Mike Moran suggested ( http://www.lugnet.com/robotics/?n=4021 ) that
you could use a tether with one fixed end and the other end attached to the
robot to gather cans. No-one replied that it would be cheating.
Also, you could use string to pull yourself (or simply guide yourself) back to
the doorway of the room when it's time to bring the can back to the start
point.
- Robert Munafo
In lugnet.robotics, Robert Munafo writes:
> > The simplest way to do this is to build a device that emits a sweeping light
> > signal, similar to a lighthouse, and a blinking signal synchronized to the
> > sweep. Unlike a lighthouse, you want it to sweep back and forth (otherwise
> > there are problems with wires getting twisted).
> > [...]
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