PRESSURE CONTROLLER operating manual
25
Tuning the PD/PDF control algorithm
The controller’s default control algorithm (PD) employs pseudo-derivative
feedback (PDF) control, which uses two editable variables:
•
The larger the
D
gain, the slower the controller will correct errors
between the commanded setpoint and the measured process value.
This is equivalent to the P variable in common PDF controllers.
•
The larger the
P
gain, the faster the controller will
correct for offsets based on the size of the errors and the
amount of time they have occurred. This is equivalent
to the I variable in common PDF controllers.
Tuning the PD²I control algorithm
The controller’s PD²I control algorithm (also called PDDI) is used to
provide faster response, most commonly in dual-valve flow and pressure
controllers.
•
The larger the
P
gain, the more aggressively the
controller will correct errors between the commanded
setpoint and the measured process value.
•
The larger the
I
gain, the faster the controller will
correct for offsets based on the size of the errors
and the amount of time they have occurred.
•
The larger the
D
gain, the faster the controller will predict
needed future corrections based on the current rate of
change in the system. This often results in slowing the
system down to minimize overshoot and oscillations.
