Subject:
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Re: GPS Reality?
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 11 Apr 2005 04:02:40 GMT
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Original-From:
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Steve Baker <{sjbaker1@airmail}saynotospam{.net}>
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Viewed:
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1113 times
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John Barnes wrote:
> I am just hoping that sooner or later there's going to be a breakthrough, but I
> cannot imagine what kind of technology it might involve. RF and ultrasonic
> solutions are plagued by multipath problems and light suffers obscuration.
> Electrostatic and magnetic fields are only good for a few feet unless large
> energies are used.
Humans and most animals have evolved to solve this navigation problem. The
result isn't 100% perfect (as anyone who ever got lost walking in the woods
will tell you). They use their eyes and a continually updatable mental
map. That's the ideal solution since it depends on no external sources
except the natural light that's floating around everywhere. Even in the dark,
night vision technology into infrared and radar is a workable solution.
The problem is that it all depends on reliable computer vision - and that's
just too far from being workable - especially in small devices.
What we need is a simpler/lower cost intermediate solution while we wait for
the computer vision researchers to make it mature, reliable and cheap.
I think it's all about using MULTIPLE techniques - and having fallback
strategies when one or more of them fails. This isn't a particularly
neat or easy solution - but it's within our technological grasp.
One thing that can help is to have the robot do dead reckoning between accurate
'fixes'. If your speed and direction measuring gear is reasonably good then
you can go a reasonable distance/time between getting reliable fixes. You
can even move around to try to get a more reliable fix.
Humans can use this mode too. Suppose you are navigating with a GPS and
it doesn't get a good satellite lock under heavy tree canopy after it's
soaked with recent rain. Humans are easily able to walk in approximately
the right direction without a GPS fix for some distance. If you think you
are getting off-course, you can look around for a clearing in the trees,
go and get a decent fix - then off you go on dead reckoning again.
This sort of thing could work with robots too.
If you are using light and did something like mount a laser on the ceiling
of the room that scans back and forth across the floor of the room. You
could broadcast a radio signal continually reading out the position of the
laser on the floor. Whenever the robot detects laser light shining on its
roof, it notes the most recently radioed coordinates and knows exactly where
it is. This is GPS for robots - but just like real GPS, it dies when you
drive under a table.
But so long as the robot is doing speed and direction monitoring between
laser readings, it still has a reasonable idea of where it is. However,
as time goes on, it's position and heading get less and less accurate.
But if the robot knows roughly how fast that accuracy degrades - and
remembers how it drove after it got under the table, (or better still,
has a map of routes that lead out from under the table that it built
earlier) it can drive back out once in a while to get an accurate position
fix again.
But everything depends on the environment. What I just described would
be great for a robot vacuum cleaner - but would be hopeless for a robot
that cleaned out your air conditioning ducts. However, in that case, you
could put bar codes every foot or two along the duct and have the robot
read that code to know where it is whenever it happens to pass one of them.
Between accurate position fixes, it would again have to use speed and direction
estimates.
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://www.sjbaker.org
Projects : http://plib.sf.net http://tuxaqfh.sf.net
http://tuxkart.sf.net http://prettypoly.sf.net
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Message has 2 Replies:
 | | Re: GPS Reality?
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| I think by setting many mini Darpa challenges, we can set the larger hobbyist community on it, and somebody is bound to come up with some crazy yet neat solution we havent yet. As I see it - even if nobody actually hit the goals, by awarding the (...) (19 years ago, 11-Apr-05, to lugnet.robotics)
| | | Re: GPS Reality?
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| "Steve Baker" <lego-robotics@crynwr.com> wrote in message news:4259F6E0.708040...ail.net... (...) where (...) I know of a group of students at the university in my town that have solved this GPS problem for a limited area. But it also have the (...) (19 years ago, 13-Apr-05, to lugnet.robotics)
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Message is in Reply To:
| | Re: GPS Reality?
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| (...) Yep! Also known as "the short range navigation problem". Everyone from DARPA to DoD to every would-be maker of a reliable automated lawn mowing system wants this. It is an amazingly hard problem which I graple with on a day to day basis as my (...) (19 years ago, 10-Apr-05, to lugnet.robotics)
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