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View Poll Results: What is your autonomous mode strategy?
Line-tracking 23 38.98%
Dead-reckoning 37 62.71%
Seek-Enemy-Stack-and-KILL!!! 14 23.73%
Other - please list. 15 25.42%
Multiple Choice Poll. Voters: 59. You may not vote on this poll

 
 
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Unread 16-01-2003, 23:43
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Re: Dead reconing

Quote:
Originally posted by bigqueue
When people say dead-reconing, are they talking about simple "timing" of moves and turns, or are you talking about having wheel encoders and such.

Big difference....
Dead Reckoning is ANY method to keep track of your position that uses INTERNAL knowledge of where you started plus knowledge of your actions instead of an EXTERNAL location reference source.

This can be accomplished by watching wheel revolutions, integrating each motor's speed over time, watching an internal "inertial guidance reference" brick, etc... And yes, this IS a programming problem!

ALL Dead Reckoning systems have drift problems over long distances, long times, or number of moves. Errors accumulate. The advantage is low cost.

The question boils down to "is it good ENOUGH for what I want to do"? Over short distances, times, and moves, Dead Reckoning is pretty good. But cruise the arena long enough, spin your tires once, be shifted by hitting an opponent, wall, or unexpected object, wait too long and your reference drifts, or add up too long a list and your resolution errors accumulate, and you no longer have a CLUE as to where you are.

BTW, as a piece of trivia, "Dead Reckoning" actually evolved from the homonym "Ded. Reckoning", which in turn was the abbreviation of "Deductive Reckoning". Deductive Reckoning is the ORIGINAL term for the method of "deductively computing" where your sailing ship at sea was at when you couldn't see the stars as an external reference. You'd use your compass, and every so often toss out a knotted rope and counted "knots" unreeled to a timepiece. That gave you your heading and speed. (Hence the nautical term for speed is in "knots"...) You integrated it in your logbook over time to estimate your position, until you could see stars or sun again. The spelling simply mutated over time from people hearing sailors speaking the abbreviation.

Some day, I think it would be GREAT if FIRST put coded retroreflectors in the corners of the field and we had enough parts and CPU crunch to have an EXTERNAL navigation reference for the autonomous phase!

- Keith
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