PID loop tuning

[handee]

Hi, we're trying to control a modulating steam valve to a using a controller that seems to have four tunable terms. Here are the current values:
PbH 16.6
Intr 65
Rset 50
Driv OFF
Question is, what are the four terms? I recognize proportional band, integral, and derivative, but what's rset? I thought reset was the inverse of the integral term? Any thoughts? TIA!

Fran McConville

 

[nbucska]

Initial (reset ) value?

<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[jsummerfield]

Search for PID and Zigler Nichols.
PB is proportional band, a.k.a. proportional or gain.
I is Integral a.k.a. reset
D is Derivative a.k.a. rate

John

 

[handee]

Thanks folks, I determined that the Rset is a "manual reset" parameter that this controller features in addition to the P, I, and D parameters. But don't ask me what it actually does...

Fran McConville

 

[naprirfan]

P = proportional or gain, the one you got from the equation of response graph

I = Integral, for minimizing the offset.

D = Derivative, for high respon and less dead time

rset = set point value

the integral and derivative constant is derived from the ziegler nichols, ciancone, and many method

Regards,
Napz

http://www.enginework.net

 

[Guidoo]

Manual reset is same as bias. For a proportional only controller, it is the output of the controller when there is no there is no error (so process value is same as set point). If you have for example a level controller that acts on a control valve in the liquid outlet line, this control valve will be partially open when there the liquid level is at the setpoint. You can have the integral term (or reset) of the PID controller handle this, or this is done by the bias term (or manual reset).

See

http://www.jashaw.com/pid/description.htm

 

[handee]

Bias - that's it! Thanks Guidoo.

Fran McConville