Re: [foxboro] PID Equations
- From: "foxpat" <foxpat@xxxxxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Thu, 17 Mar 2011 21:37:47 +0100
In addition to the mode option the SPLLAG effects the behaviour of the
control action on setpoint changes.
If SPLLAG is 1.0 then the P action will be 100% on error (so same action on
PV and SP).
If SPLLAG is 0.0 then the P action will be only on PV changes so, no P
action on setpoint changes.
This allows for a tight tuning while preventing large MV moves in case of
operator setpoint changes.
Example for use: temperature controls on reactor which manipulate quench
flow; these need to respond fast on temperature fluctuations (and therefore
have a relative low P value (high gain) but should not overshoot when the
operator changes the setpoint.
A typical setting for SPLLAG would be 0.2 wich means that the P action on
setpoint changes is multiplied by 0.2 (so if PBAND would be 100 it would
result in a PBAND of 500 for setpoint changes but would remain 100 for PV
changes).
So; SPLLAG = 1.0 -> P on Error,
SPLLAG = 0.0 -> P on PV only.
PITAU works well on control loop with pure deadtime and can be benifitial if
you have problems with 'sticky' valves. (output increases, nothing happens
for a while until friction is overcome and of it goes; sort of deadtime)
This is a workaround though as PITAU will be slow on setpoint changes!
Regards,
Patrick Martens,
-----Oorspronkelijk bericht-----
Van: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
Namens Ravindrakumar Ratnakumara (PLM/MLNG)
Verzonden: donderdag 17 maart 2011 9:09
Aan: foxboro@xxxxxxxxxxxxx
Onderwerp: [foxboro] PID Equations
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Hey List,
Noob here. What are the available PID equations on Foxboro? I've heard =
of P on Error and P on PV, does this refer to these equations? Why do we =
need each of these different equations and on what circumstances do we =
choose to use them?
Thank you and best regards. J
TES/5 - Making Automation Work!
RAVINDRAKUMAR RATNAKUMARA
APC Engineer | TES/5 - Technical Services Department | MLNG - Bintulu | =
' Tel: 086 85 3765 | =C8Mob: 012 563 3354 | 6 Fax: 086 252 037
=20
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