I have very similar issues described in this unresolved thread when trying to make our differential drive follow a trajectory. Namely: the robot is shuddering a lot when trying to follow the trajectory, and doing so, of course, it does not track well.
Interestingly, I can even reproduce this issue in simulation, which baffles me, since simulation is using the same gains given to the trajectory generator!
Here is the result when trying to follow a path in the simulation, after disabling both the Ramsete and the PID controllers. The chassis is not following the reference at all!
What I have done so far:
- Made sure the odometry is spot on. On the field, it is accurate within a 1-4 centimeters. Angle is accurate too, and all signs are tracking the ones described in the documentation
- Ran the SysId multiple times to make sure no one-off chance event was interferring. [Results are availabe here].(CaractérisationWestcoast - Google Docs).
- Troubleshooting page is advising to check measurements, and in particular wheel diameter, which I did several times. We are using 4" wheels, but I measured them as precisely as I could. Also verified the gearing ratio to make sure it matches what the vendor is advertising.
- Although my best guest would be my sysid settings being wrong, I verified them multiple times:
Full code here. Main classes involved in path following: PathFollowing, WestcoastOdometry, and ChassisId.
I would appreciate a lot any guidance on what to check next 