Regulator Tuning – Guidance

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There is very little if any information on selecting the target Bandwidth (BW in radians/second) or response for the drive regulators used in web handling. We can safely assume the drive vendor’s instructions for tuning the torque loop are adequate.

For the speed regulator, the guidelines are either to tune for the standard (out of the box) BW. This may be 5 radians/second. Another common option is to tune As Fast As Possible. Tuning for the fastest regulator possible will give a different response for each section of the line.

Without any constraints, tuning as fast as possible is a good rule. Watch out for instability and wear and tear on the drive train.

Tension regulators are also tuned as fast as possible. Again we need to ensure there is no instability. In a paper mill, this may give a Bandwidth of 0.5 radians/second. With a servo drive on small equipment, the Bandwidth may be 10 radians/second.

The web will indicate that speed or tension regulators are too slow. A spindle winder tension regulator must recover after a winder cutover before the next cutover takes place. In fact, the faster the better, because if tension is bad at the cutover, any folds or wrinkles form the inner wraps on which the entire roll is based.

We as an industry need better guidance on speed regulator and tension regulator tuning.

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