[vhcook]

With mechanum, you will need encoders on all four wheels to get an accurate position reference, and you'll have to correct for wheel diameter and the vector of the force applied by the angled rollers. I have some detailed notes from our development this season, and I'll see if I can put together a white paper over the next couple of weeks. There is a bit of slip because of the rollers, but you can get reasonably accurate readings.