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Originally Posted by Matt Adams
Accelerometer is the way to go if you can get it to work.
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Accelerometers seem like the perfect solution in theory. However, to get from acceleration to position, you need to do a double integration. What this translates to is that even a slight amount of noise will be magnified by the integration and your positioning system will think it's moving when it's not. In our experience we encountered far less error due to wheel slip with our positioning system than we would have due to the double integration problem. Our robot would end up within a foot or so of our target location at the end of a 15 second autonomous round, and that was after doing complicated movements. Inertia-based systems have been known to drift by twice that amount or more when they're sitting still on a table for 15 seconds.
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I thought that if you could monitor rpms at a given wheel, and also monitor the current going to the motors powering that wheel, you could compare the two values and experimentally determine whether your wheels are slipping.
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We actually had everything designed to do that this year but ran out of time to do the software. We had fabricated a PCB that implemented our current-sensing circuit from 2002 which attached to our 2003 positioning system. Would have been fun to try, but part of the reason we let it fall to the wayside was because our accuracy without it was much better than we had expected, making it unnecessary.