Alicat Scientific EPC Series Manuel d'utilisation - Page 14
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Tuning the PD²I control algorithm
The EPCD controller's PD²I control algorithm is used to provide faster
response, and high-performance swapping of the operation of the inlet and
exhaust valve. This algorithm uses typical PI terms and adds a squared D term:
The larger the P gain, the more aggressively the controller will correct
errors between the commanded setpoint and the measured 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.
Warning:
!
experience significant performance issues if switched to PD/PDF.
Troubleshooting valve performance with PID tuning
The following issues can often be resolved by adjusting the PID gain values
for your flow controller.
Fast oscillation around the setpoint
PD: Reduce the P gain in decrements of 10%
PD²I: Increase the P gain in increments of 10%, and then adjust the I
gain to fine-tune.
Overshot setpoint
PD: Reduce the P gain in decrements of 10%.
PD²I: If D is not 0, increase the P gain in increments of 10%.
Delayed or unattained setpoint
PD: Increase the P gain in increments of 10%, and then decrease the D
gain by small amounts to fine-tune.
PD²I: Increase the P gain in increments of 10%, and then increase the I
gain to fine-tune.
✓
Note: Valve tuning can be complex. Please give us a call, and we'll be
happy to guide you through the process. Or, visit
detailed instructions
EPCDs are only intended for use with PD²I tuning and may
14
alicat.com/pid
for more