[JohnGilb]

Ether, your follow wheel mounting assumption is correct. They were positioned as in your diagram, and they were omniwheels.

We did use them to calculate a rotation rate, let's call that Rotation_Follow. We also had rotation from the gyro, let's call that Rotation_Gyro.

We found that Rotation_Follow wasn't as good as the Rotation_Gyro, we suspect due to minute wheel scrub and small errors accumulating, but it did not suffer from drift. Consequently, we used Rotation_Gyro exclusively, but ignored any change in rotation while Rotation_Follow was 0 (typically at the start of the match before the robot was moving anywhere, or during testing when the robot spent a lot of time on a bench or disabled). This eliminated a large part of our gyro drift.