We are having inconsistencies with the PID control blocks in the Yokogawa Centum VP control system.
In this case, we are trying to control air flows with PID flows and function blocks to linearize the performance of the butterfly valves.
When set in manual mode, the valves will stroke and will produce linear flow. The response is immediate and consistent.
When set in automatic, we try to "take the reset out of the loop". We have tried to do this either by setting the I value to 0.1 to 10000 seconds.
It is apparent that the PID control algorithms are coupled.
I am aware that there are "auto-tune" functions and that there are additional packages that we could purchase that could also address this.
However, is there a way to set the P without setting the I and/or D?
Or is there a PID tuning process specific to the tuning of a Yokogawa CENTUM VP DCS PID loops?
I don't think it's possible to actually remove the I tuning parameter to 0 but if it's set to 10,000 then this is effectively removed. Be aware that:
* If integral is removed then the controller is exposed to steady state errors.
* The Yokogawa CentumVP PID function block automatically reduces the calculation frequency based on the integral time. To avoid this change the builder setting for "Control Period under the "Control Calculations" tab to "1" instead of automatic determination (then is will process every 1 second scan).
The derivative component can be disabled by setting D to zero.
I hope that helps.