Re: [foxboro] foxboro Digest V8 #251

I have used calc blocks to turn Integral action on and off as you
describe and it works well. Have not used the non-linear controller,
but, will keep it in mind. I was just answering the call for suggestions
to improve IA. I believe that Delta V offers Integral deadband and I
think it is a feature worth copying.

Thanks for the response
David
 

-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Rguercio@xxxxxxx
Sent: Monday, July 28, 2008 1:10 PM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] foxboro Digest V8 #251

In a message dated 7/26/2008 01:04:00 Central Daylight Time,
foxboro@xxxxxxxxxxxxx writes:
How  about adding an Integral deadband to PIDA blocks, so that when the
process  is within the deadband, the Integral action is turned  off


I do this regularly with my advanced level control application  (ALC).
It is pretty easy to use a calculator to flop your connected INT
parameter between
9999 (inside deadband) to whatever you want when outside the  deadband.
The nonlinear controller, by the way, works great (unlike the  one
Honeywell put in and didn't support in Plantscape), but I usually only
double the gain outside the deadband, and have gone as high a tripling
it for  special circumstances.  Remember, you don't want the CV to come
barreling  in and out the other side of the deadband because of how
severely you turned it  around when outside. 
 So the original tuning has to be able to take back  over once the
deadband is entered, and you need to be somewhat judicious in  choosing
the width of the deadband, which in the nonlin controller, does not
have to be symmetric about the setpoint.
 
RGC
12803 Josey Creek Ct.
Cypress, TX 77433
713-805-8742  cell
281-256-1111 home office/FAX
281-256-1333  home



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