[Alan Anderson]

Are these drive motors? If so, is your robot up on blocks? Trying to tune a closed-loop controller with no load on the wheels is going to be a frustrating exercise, as there is going to be a lot of overshoot and very little damping.

You might be able to get it to work adequately if you limit the rate at which the motor speed command can change. But it's really going to have to be run on the carpet in order to get it dialed in properly.