PIDE Windup Limiting Not Working

Hi all,

I have primary and secondary control loop cascaded together and am using the WindupHIn/Out and WindupLIn/Out to prevent the CV of the primary loop increasing/decreasing when the CV of the secondary loop is 100% or 0%.

See attached for a screenshot of the primary level loop with WindupHIn on. However the CV continues to increase! The help file says "The WindupHIn and WindupLIn inputs are ignored if CVInitializing, CVFault, or CVEUSpanInv is set." However these are all cleared.

Is there some trick to get this to work? I've seen this before but have always just shrugged my shoulders and moved on. I've tried just writing a one to the input rather than the tag, but still no good.

Thanks.

Maybe see the section on Cascade Control here:
http://literature.rockwellautomation.com/idc/groups/literature/documents/wp/logix-wp008_-en-p.pdf

"You should also wire the WindupHOut and WindupLOut outputs of the secondary to the WindupHIn and WindupLIn inputs on the primary. When the secondary hits an output or setpoint limit, it will set the appropriate Windup output which will cause the primary loop to stop integrating in that direction. "

This is exactly what I've done, but the primary loop keeps going.

I notice you're not using "assume date available" for those inputs of your primary as indicated in the PDF I referenced. (And am not sure if that's the problem).

Gave it a go, still no good. Assume data available is generally just to resolve FBD loops as in the PDF or to control data flow, given my PIDE blocks are in separate routines it wouldn't be required.

I've also tried just writing a 1 direct to the input and it still doesn't prevent windup.

You're not using the Emulator are you?

Are you positive that the primary CV change is from INTEGRAL windup? The Windup controls have no effect on the proportional (or derivative) gain.

given my PIDE blocks are in separate routines

Click to expand...

if all else fails to work, I'd try putting them both in the same routine - just as an experiment ...

if that works, then read up on how a Function Block Diagram "freezes" all of the inputs to a sheet - before it begins executing/scanning that sheet ... just GUESSING - but maybe that's having an effect on the operation of your system ...

Are your WindupLOut and WindupHOut outputs of the secondary functioning properly (ie. the appropriate one gets set as the loop winds up or down to an output limit)?
Also, what Mr. Beaufort said...

"WindupHIn
BOOL
Windup high request. When set, the CV cannot integrate in a positive direction.
"

It can't integrate, but it can still proportion/derive.

I would use CVPrevious/CVSetPrevious inputs for the functionality you are after.

Annoying, but there you go.

AustralIan said:

"WindupHIn
BOOL
Windup high request. When set, the CV cannot integrate in a positive direction.
"

It can't integrate, but it can still proportion/derive.

I would use CVPrevious/CVSetPrevious inputs for the functionality you are after.

Annoying, but there you go.

Click to expand...

I guess that's what I'm seeing then. Kind of useless then, as if SP > PV and CV = 100% then why the hell would I want the SP to continue increasing...

Will have a go with CVPrevious/CVSetPrevious

Thanks