Programming Issues with Crab Drive System

[engunneer]

Another important thing to do is to make sure you calibrate the PID with the correct load and friction conditions. Make sure your robot weight is approximately right, the CG is in about the right place, and there is no binding in any of the steering bits.

How are you calibrating the PID? Are you able to command a "step move" or velocity profile, then graph the "commanded" and "actual" positions?
Can you change your PID on the fly (without a re-download)? If you can do both of those, you have the tools to make a great PID controller.

Lastly, see if you can add some additional parameters into your PID loop. I suggest learning about Velocity Feed-Forward (adding some of the command velocity into the output, without waiting for the P, I, and D parameters to detect it) and Friction bias (always adding a small amount to the motor output in the same sign as the direction you are trying to turn.)

Post any graphs that you can, or any questions here, and i'll be happy to try to explain.