Subject:
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Re: localization (was re: GPS)
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 12 Jan 2006 17:01:37 GMT
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Original-From:
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Chris 'Xenon' Hanson <xenon@3AVOIDSPAMdnature.com>
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Viewed:
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2179 times
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John Barnes wrote:
> I have tried all sorts of tricks with ultrasonic stuff, you're right :)
;)
> There are a couple of different schemes for the ultrasonic beacon type things.
> You can have ones which are triggered from the 'bot via radio or IR. I've tried
> the IR one. A really bright IR pulse can get around the same kinds of corners
> that ulrasonic can, although once the sounds has started going round corners,
> all bets are off anyhow.
Right. I'm assuming something that basically assumes Line of Sight between bot and 3 or
more beacons, just like GPS. GPS doesn't deal well with multipath either. ;)
> The other thing you have to do is be able to address
> each beacon so you can request which one transmits. Then you pick the earliest
> arriving pulse, 'cos the later ones will be due to multipath.
Right. Code a beacon ID into the IR pulse you send out.
> And if they all
> transmit at once, the mixture of coincidentally equal distances to two or more
> beacons and the chance of multipath effects from closer beacons interferring
> with signals from others further away makes individual arrival times of each
> beacon's pulse hard to do.
Right. You'd have to make them only ping when addressed individually, in order to get
any kind of cohesive signal.
> It is more difficult for a beacon to encode it's id
> in its transmitted pulse (due to limited modulation bandwidth) than it is for
> the requesting radio or IR pulse to have id information in it.
Agreed.
> I've also played around with multi-sensor element phased arrays too to get
> signal arrival angle, but you need a lot of sensors to get a decent result and
> that gets expensive quickly.
Yeah, I hadn't even considered it for that reason.
It sounds like you've already done all of the things I'd been plotting. As you mention,
getting the data into the RCX wouldn't have worked very well, but within the limitations
outlined above, did the system itself work ok for position detection?
> JB
--
Chris 'Xenon' Hanson | Xenon @ 3D Nature | http://www.3DNature.com/
"I set the wheels in motion, turn up all the machines, activate the programs,
and run behind the scenes. I set the clouds in motion, turn up light and sound,
activate the window, and watch the world go 'round." -Prime Mover, Rush.
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Message is in Reply To:
 | | Re: localization (was re: GPS)
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| (...) I have tried all sorts of tricks with ultrasonic stuff, you're right :) There are a couple of different schemes for the ultrasonic beacon type things. You can have ones which are triggered from the 'bot via radio or IR. I've tried the IR one. (...) (19 years ago, 11-Jan-06, to lugnet.robotics)
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