ARTDrive V2 series - Instruction Manual Chapter 7 Appendix • 343
7.5.8 Application Note: Dynamic Change of the PI Block Integral Gain
The higher the diameter ratio of the controlled winder is, the lower is the
value at which the PID integral gain is usually set. A too high value allows a
good regulation with low diameters but causes strong system coggings when
higher diameters are present.
On the contrary, too low values of the integral gain could cause, with a
minimum diameter, a movement of the dancer position, as compared to the
electric 0 position, directly proportional to the line speed. It happens because
the integral component charge or discharge is performed in a period of time
shorter than the diameter changing time.
Dancer Winder
300 mm
(1 ft)
Diam
3,8“
38“
@ Big diam to move
1 ft of dancer = 1/3REV
@ Sm diam to move
1 ft of dancer = 1REV
Figure 7.5.8-1: Example with a Small and Big Diameter
In case of high diameter ratios, it could be necessary to change dynamically
the values of the PI P and I parameters according to the present diameter.
As the output of the PI Block is inversely proportional to the diameter, it must
be connected as the abscissa of the PI gain adaptive.
PIGP ref src = PID PI out mon
The thresholds and gains have to be set in order to obtain a gain Profile
equal to the one shown in the following figure.
Consider to control a winder with a 1/10 diameter ratio.
The regulator integral component must be inversely proportional to the
diameter.
The value of the PI output PID parameter is already in compliance with this
rule, as it changes according to the ratio
Φ
0
/ Φatt.
Where: Φ
0
= winder minimum diameter
Φatt = winder present diameter
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