Posted by Matt Leese at 2/6/2001 12:10 AM EST
Other on team #73, Tigerbolt, from Edison Technical HS and Alstom & Rochester Institute of Technology.
In Reply to: Difference in forward/reverse drill motor speed
Posted by Patrick Dingle on 2/5/2001 11:38 PM EST:
Yep, noticed this one awhile ago. You can work around it several ways. The more correct solution (i.e. the mechanical one) is to either mount the drill motors turning the same direction or put an extra gear in one side so they both turn the same direction. The less correct solution (i.e. the programming one -- Matt's Law: never fix something in programming if it can be done mechanically) is to wire a potentiameter onto the control system that will scale down one of the drive PWM outputs. You then drive the robot over a distance and fiddle with the pot until you get the robot driving in a straight line. This does lower the overall top speed of the robot however (you have to scale down the motor turning the forward direction). This takes a little bit of finesse to get right and careful drivers who don't bump the pot.

It worked fairly well for us last year but there are a few caveats that I'll let you figure out on your own (hint: it has to do with driving in reverse).
Matt