[TheOtherGuy]

You mentioned using a caster for figuring out the actual velocity of the robot; another possible way to do this is with the accelerometer. Before kick-off we designed a quick inertial positioning system using an accelerometer and gyro based off of 111's system back in '04 (I think it was '04...). Using some trivial physics you can use a loop to keep track of your actual velocity and position. Now, we haven't actually messed around with an accelerometer at any point in our history, so I don't exactly know how accurate these are, but that was our first take on traction control.