Subject:
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NXT Motor Encoder Accuracy and Dead Reckoning
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Newsgroups:
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lugnet.robotics.nxt
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Date:
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Sun, 13 Aug 2006 04:04:21 GMT
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Viewed:
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11495 times
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Has anyone done any experiments on the accuracy of the NXT motor "move
to" block? If so, can they post their results or impressions?
I know NXT supports PID calculations to synchronize two motors and run
in a straight line. Can you use this to drive your NXT robot
accurately around the sides of a square?
There was an excellent RCX based dead reckoning robot created several
years ago called Peeves. There's a great writeup on it at
http://www.seattlerobotics.org/encoder/200108/using_a_pid.html. Peeves
was built for a dead reckoning contest held by the Conneticut Robot
Society. Robots started in the middle of one side of a square with 6.5
feet sides. Robots had to traverse the square using dead reckoning
without going more than 9 inches from the sides of the square. The
winner was the robot that finished closest to the starting point.
"Peeves consistently finished within 3 centimeters of its starting
position." Can/has the same performance been achieved with NXT using
the standard NXT-G programming language? Peeves was also fairly slow -
3.6 inchese per second.
Peeves used a PID based algorithm including fairly complex equations
for calculating and correcting for angular deviation. The equations
used a lot of trigonmetry based arithmetic (including approximations
for 'sin' and 'cos" functions). It's all described in the above
reference.
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Message has 3 Replies:
 | | Re: NXT Motor Encoder Accuracy and Dead Reckoning
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| Dick, the article you referenced with the PID controller is excellent. I spent a lot of time trying to do a straight line with an RCX model a few years ago, but with a different approach: It was track-driven and the drive shaft extension on each (...) (18 years ago, 13-Aug-06, to lugnet.robotics.nxt)
| | | Re: NXT Motor Encoder Accuracy and Dead Reckoning
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| (...) I've played with it a good bit. It seems to be extremely accurate, in that one motor will slavishly follow the other - you can do demos like set a Move block to drive forward 10 rotations, and while it's trying to do that pick up the robot and (...) (18 years ago, 13-Aug-06, to lugnet.robotics.nxt)
| | | Re: NXT Motor Encoder Accuracy and Dead Reckoning
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| (...) ... (...) Yes. Very easily. I took my floor cleaner robot, Rosie: (URL) a two-block NXT-G program (in a loop): (URL) created a robot that I think has the accuracy of "Peeves", as seen here: (URL) appears to return within a couple cm each time. (...) (18 years ago, 13-Aug-06, to lugnet.robotics.nxt)
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