Subject:
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Re: Navigation using landmarks (Was: Re: lasers and RCX)
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 28 Jun 2002 06:50:49 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail.&antispam&net>
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Reply-To:
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sjbaker1@NOMORESPAMairmail.net
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Viewed:
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889 times
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PeterBalch wrote:
> Steve
>
>
> > > ultrasonic beacons
> > I wonder how you estimate that error?
>
>
> Tradition had it that with three radio beacons and three hyperbolae you'd
> get three lines intersecting to form a triangle and the boat was most
> likely inside the triangle. That was nonesense. You've a 50% chance of
> being on either side of a line so a 1/8 chance of being in the triangle.
I meant the error due to things like refraction around solid objects,
reflections, etc. Also - I didn't mean estimating and correcting for
it at runtime - I just wanted an idea of what sort of magnitude of error
those effects presented.
> > If you had the sound generation system emit an IR or radio pulse in time
> > with each 'squeak', you could possibly get all the information you need
> > with just two beacons.
>
> More or less.
>
> Two beacons plus IR gives you two hyperbolae with two intersections. You
> could arrange it so one of the intersections was outside the room.
Yes - only if you know the exact time of the emission of the squeak,
you have two intersecting circles - which makes the math a lot easier!
> > How hard is it to reject sounds from sources other than the acoustic
> > emitters?
>
> With ultrasonics, probably not too hard. And you've got a good idea when to
> expect each sound.
Another good reason to use an IR pulse to announce the 'launch' of the sound.
> > we use acoustic head-tracking systems
>
> Hmmm. What about all the other ways people keep track of humans heads,
> hands, etc.?
>
> How about three large coils under the carpet? Each generates a small
> magnetic field a different frequencies. The relative strengths of the
> fields tells you where you are.
Well, there are many reasons why we chose audio - there is a lot of metalwork
in a simulator - and that's hard to compensate for with magnetic or inductive
approaches - we also have *BIG* video projectors which have large magnetic
coils on them. Also, we need near darkness inside the simulator cab and since
there are times when the pilots will be wearing night-vision goggles, we can't
use lasers or infra-red LED's or a variety of other tracking technologies.
But - yes - there are a large number of other techniques that appear to work
quite well in less specialised environments.
I was wondering whether one of those new fancy optical mice which use a tiny
camera to watch the motion of your desktop might be adapted with a suitable
lens to track the motion of a robot.
----------------------------- Steve Baker -------------------------------
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