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Subject: 
Re: robotica on TLC
Newsgroups: 
lugnet.robotics
Date: 
Fri, 6 Apr 2001 19:22:40 GMT
Reply-To: 
micahx@kih.net+Spamcake+
Viewed: 
4057 times
  
Steve Baker wrote:

"Micah J. Mabelitini" wrote:

Steve Baker wrote:

What I think it would take would be to add a rule that every robot must
contain a GPS unit and broadcast it's position continually for the other
competitor to pick up.

GPS wouldn't work. Even though the government disabled Selective
Availability last year, commercial GPS still doesn't achieve an accuracy
better than several meters.

Differential GPS (where you add a 'ground station') gives you plenty
of precision - even without the low order bit scrambling thing.

It's not good for telling you where you are relative to the planet - but
relative to the ground station, it gets you within a couple of centimeters...
plenty for these meter-wide 'robots'.

Yeah, DGPS would probably be accurate enough, assuming you could get
around the no-lock problem.

I would imagine that for GPS to be suitable
in such a competition, it would require an accuracy of no more than a
few inches, and would require that all of the platforms were equipped
with *exactly* identical GPS modules manufactured with very rigorous
tolerances.

The TV company would presumably supply those in order to avoid cheating...
and they could be pretty high-end units.

Also, getting a lock inside any building is difficult and
unreliable at best, and it appears that these types of competitions are
generally held in large steel buildings, an environment totally
unsuitable for receiving a GPS lock.

Dunno about that...you could well be right.  Does the presence of the
ground station inside the building fix that?   I have no idea.

I believe the on-board GPS receiver would still need to fix on the
Navstar constellation, regardless of whether or not it was a
DGPS-augmented system. That's not going to happen in a large
warehouse-type building.

What about some sort of standardized IR beacon pulse on an
omnidirectional emitter, and equipping the platforms with a servo-driven
rotating unidirectional detector? Since all of these competitions seem
to be one vs. one

(No - BattleBots does an 8 robot 'rumble' from time to time - and the
British Robot Wars series has several 'games' where there are many
machines in the arena at once - with a set of robots designed by
the BBC (The "house robots") in nearly every competition.)

I wasn't aware of the 8 robot thing (I've only seen BattleBots
once)...that sort of situation would definitely complicate matters.

have standard emitter designs with two pulse
frequency settings. Then, one competitor could set their locator system
to Mode 1, and the other to Mode 2, preventing a platform's emitter from
interfering with its own detector.

Yes - something like that would work - but anything on the outside of the
case would get smashed off in short order I think...also many of the
designs have to work upside-down as well as right side up.

Yeah, I considered that. It would no doubt be hard to engineer such a
system in a rugged enough fashion to be reasonably reliable.

Since the arena is fixed, you could put light detectors in the floor
and have the TV company track where the robots are by knowing which
detectors are covered up...then broadcasting the locations of the
two machines by radio...there are LOTS of ways to make that kind
of thing work.

Anyway - the point is that to make a viable "true" robotic competition,
there would have to be some kind of mandatory tracking mechanism...you
could argue indefinitely about what it should be - but it's pretty
clear you could solve it.

Agreed. I think you're on the right track with the whole "DGPS stations
inside the building" thing though. But, since you dont need absolute
global positioning, only a relative position on a local coordinate grid,
perhaps eliminate the GPS altogether and just set up triangulation
beacons around the arena?

--

Regards

Micah J. Mabelitini - LUGNET #918
The University of Kentucky
SECC Middlesboro Academic Skills Resource Center
accutron@kih.net - http://www.users.kih.net/~micahx/



Message is in Reply To:
  Re: robotica on TLC
 
(...) Differential GPS (where you add a 'ground station') gives you plenty of precision - even without the low order bit scrambling thing. It's not good for telling you where you are relative to the planet - but relative to the ground station, it (...) (23 years ago, 6-Apr-01, to lugnet.robotics)

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