Quote:
Originally Posted by DonRotolo
I'd like to see someone answer the original question though with a more rigorous treatment.
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Quote:
Originally Posted by TheHolyHades1
The other reason for necroing this thread is to search for what Don and I are asking for - namely, the more rigorous method of doing it.
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I worked myself through the equation I believe you are looking for late one night. As far as I know it is correct:
Coefficient of friction * tread width * weight supported by the wheel = force required to turn the wheel
If you want to get fancy:
Coefficient of friction * √((tread width)² + (tread length in contact with the carpet)² ) * weight supported by the wheel = force required to turn the wheel
tread length in contact with the carpet - if you were to look at a side profile of the wheel and the carpet so that you are seeing the wheel as a circle and the carpet as a long, thin rectangle, this would be the distance of a straight line from the first point that the wheel and carpet intersect to the second point that the wheel and carpet intersect.
When calculating the weight supported by each wheel for non-crab, 4+ wheel swerves remember the wobbly four legged chair/stool in your kitchen. At any given time there are only three legs of it bearing its weight, and the same can be true for your swerve. This may not always be the case, and even if it is you may be able to dig deep enough into the motors' torque to compensate without stalling them. Either way it's at least something to consider.
Some other things you may also want to consider are additional weight you may pick up during the course of a match (i.e.: game pieces), what happens if another robot gets under your bumper or crossing the bump in 2012 and you are left with fewer wheels than you designed for in contact with the ground, as well as any other scenario you can think of that may compromise the turning ability of the wheels in your swerve. While easily over looked, not thinking about things like these could end up costing you a match or two through the course of a season or worse yet robot functionality, but that's just my two cents.