Re: [foxboro] PID Out Block Increase
- From: Cyrus Taft <cwtaft@xxxxxxxxx>
- To: foxboro@xxxxxxxxxxxxx
- Date: Wed, 1 Oct 2008 18:24:36 -0700 (PDT)
Corey,
Yes this is what I was thinking of doing. I see what you mean about the
benefit of the one-shot approach. I'll have to figure out if it would be
possible in my situation for the PID controller output to move away from the
limit without the toggle changing also.
Thanks,
Cyrus
----- Original Message ----
From: Corey R Clingo <corey.clingo@xxxxxxxx>
To: foxboro@xxxxxxxxxxxxx
Sent: Wednesday, October 1, 2008 6:36:37 PM
Subject: Re: [foxboro] PID Out Block Increase
I got the impression it was something like this FoxCAEmail drawing
(parameter names may not be exact, going from the 1K buffer here):
PID /-->output SWCH
|-------| | |--------|
| OUT|-*--------->|IN2 OUT|-->--\
| | | | |
/->|HOLIM | 100-->|IN1 | |
| |-------| | | |
| limit-->|TOGGLE | |
| signal |--------| |
| |
\--------------------------------------/
Can't say I've done it with a SWCH block, but I have done it entirely in
CALC block code (I waffle some between the do-it-all-in-the-CALC mentality
and using extra blocks) and it worked fine. One difference I'd note is
that my CALC block code only grabbed the PID's output once when the limit
input was triggered, and thus it would let the output go down and come
back up to that point while the limit was active. This setup here would
not allow any increase from the previous scan's output at all when
limiting is active.
Corey Clingo
BASF Corporation
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