PIDController not manipulating jaguars

[gpetilli]

Originally Posted by Ether

I question whether velocity PID based on rate feedback from drivetrain gearbox encoders will allow the bot to re-establish its orientation (or even position) after an impact.

We got our velocity loops working this past Saturday (after finally solving a problem with I2C comm to different sensors in independent timed threads corrupting data). The robot clearly actively resisted any movement. When forcibly kicked two feet out of place, I was surprised but the robot actively returned to the original position and orientation . I have not had time to investigate, but I think the PID is integrating the velocity error correction (any velocity is error with a zero commanded velocity) and then "de-integrating" the error. It may also be the loop is too slow, and just happened to stop correcting the velocity error such that it landed back at the starting location.
For our application, returning was not desired behavior. We plan on adding more D term on Tuesday to see if we can limit the "integrator windup".

That all said, I agree that for the stated problem a position loop would be adequate, easier to implement and probably preferred.