AV-300i Version 2 User’s Guide
—————— Function Description ——————
Ch.1
169
The PI lim top and PI lim bot parameters can be considered, respectively, as a maximum and minimum
multiplicative factor of the feed-forward.
PI lim top = 1
PI lim bot = -1
1.16.8 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.
PI I gain PID
100
1000
PI output PID
40%
4%
max
20%
PI I gain PID =
(
att x KI)
[KI=40%]
o
100
1000
200
500
8%
500
200
Figure 1.16.8.1: 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
φφ
φφ
φ
0
/
φφ
φφ
φ
att
.
Where: φ
0
= winder minimum diameter
φ
att
= winder present diameter
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