The help provided for Auto-Tuning was adequate. Some of the procedures require some thought prior to implementing. The Auto-Tune had to be repeated multiple times as I gained understanding of just how it worked.
The Auto-Tune in the PLC I experimented with required the PID block be put into Manual mode in order to Auto-Tune. This is not an unreasonable demand, but requires thought. For a tension through speed regulator, this requires setting the speed with draw or ratio well enough to get the line running. For a tension through torque regulator, the torque must be set such that the line will run. Then the tension regulator can be Auto-Tuned.
Prior to running the Auto-Tune, a few parameters must be set up. In my case, this was the step size (10%) and the regulator accuracy (0.25%). Then the Auto-Tune button needed to be clicked. In seconds, the measurement was complete. A warning indicated the measured tension feedback did not change enough. Increasing the tension step size could be a problem with weak webs. Following Auto-Tune, the regulator gains could be set by selecting Slow, Medium or Fast response. I tried each of these.
Note that it took several tries to get the sequence correct. Understand this as “I needed the operator to rethread the line several times before the Auto-Tuning was completed satisfactorily."
The PLC Tension Regulator was then put into auto and the response of the tension regulator was checked by changing the tension setpoint. In the Slow, Medium and Fast case, there was noticeable overshoot in the actual response.
Then I used the parameters resulting from Auto-Tuning as a starting point for manual tuning. I eliminated the overshoot by choosing parameters slower than the slow response.
The attached trend shows tension during tuning, and the responses for Auto Slow, Medium and Fast parameters as well as the result of manual tuning.
The Auto-Tuning shows promise for the real world.