Quote:
Originally Posted by Dave Scheck
I would highly recommend not using encoders to determine crab position. Yes they can work, but they require you to precisely position the wheel at startup. Since the encoder doesn't tell you where you are, you could have the wheel turned 90 degrees and the RC has no way of knowing that it's not centered. Pots are far superior in this aspect because they give you an absolute position at startup and the necessary corrections can be made.
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True, but normal potentiometers have the nasty disadvantage of having a hard stop. When we did swerve drive in 2004, we broke a lot of potentiometers (especially in testing) by turning them too far. In hindsight, it might have been a better idea to use encoders, set the wheel to a known position at the start of the match, and probably have a limit switch as a backup that would be triggered (e.g.) when the wheel was straight ahead - so if anything happened, you could have a reset button that would spin the wheel until it triggered the limit switch and then would reset the encoder count. (You could also do this on the fly - every time that switch happens to be triggered, have an interrupt that corrects the encoder count.)