Re: [foxboro] PIDTAU & PID Tuning.

Rick,

In our case, with MODOPT 5 we had a SPLLAG of 1 to have a good initial =
response in the output to STP changes. To our surprise, the SPLLAG =
parameter disappeared when changed MODOPT to 8, and seemed to have no =
effect since the response was as if we had SPLLAG 0. As regards the lack =
of response to the sustained error, the INT value was 3 (not too large =
considering it is a temperature control of a fired heater). As regards =
the derivative, we used KD to damp the noise in the MEAS, so that =
shouldn't be bothering. We did not try the FBTUNE, but can do it to =
improve the tuning once we are sure it works fine.
The other concern is whether the tuning parameters should be changed =
given the fact that the algorithm for MODOPT 8 is non-interactive vs. =
product of factors for MODOPT 5. If that's the case, does anyone have =
the conversion table?
Regards,

Martin

-----Mensaje original-----
De: Rick Rys [mailto:rys@xxxxxxxxxxxxxx]
Enviado el: Jueves, 29 de Mayo de 2003 11:06
Para: foxboro@xxxxxxxxxxxxx
Asunto: Re: [foxboro] PIDTAU & PID Tuning.


While I haven't messed with the PIDTAU in a few years, I do recall that =
it
worked as expected.  Regarding the movement in output when the SPT is
changed, this is governed by the SPLLAG parameter and also by the PB.  =
For
fast response to SPT changes there is an optimal value for SPLLAG.  If =
set
to 0.0 (No output bump) then changes to SPT will be much slower (Longer =
time
for MEAS to reach SPT) and the output will only change at the reset rate
(Integral tuning parameter).  Regarding the lack of output response with =
a
sustained error, this should not occur (i.e. Somethings wrong) as the
MODOPT=3D8 has P+I+D and the integral should eventually return the MEAS =
to
SPT.  Maybe you set the I to a very large value?, Maybe noise in the =
MEAS is
being acted on with the Derivative.  You can set the D to zero.  Also =
the
PIDTAU can be tuned with the FBTUNE block and the pretune function =
(bi-polar
pulse) usually gets the tuning values very close.

Regarding the managment of PID tuning in general there are some third =
party
packages out there that can keep track of/manage tuning settings.  You =
can
find these in google by searching "PID tuning".

Rick Rys




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