PID Function

Hello!

Can someone tell me how I can adjust an PID loop. On school I learned about Ziegler and Nichols, but don 't remember how it works...
Is it still used? And is this a good method?
I also would like to know how I need do do the adjustment.
Maybe someone can send me some info of url....

Further info: The flow in a tube needs to be at a fixed value (eg. 15bar). The pressure in that tube is messured, and by opening or closing a vavle, the flow is controled.
I am using a Twido PLC of Scheider, with integraded PID functions.

thx

Ahem, try google with "ziegler nichols" and "cohen coon" and "PID tuning"

Ziegler Nichols is probably a good place to start. Try searching this site for PID, and try this link and search for Ziegler Nichols:

http://resource.controleng.com

Note that any tuning technique just gets you in hte ball park. Some trial and error are still required.

You seem to have some confusion on the physics governing your process. Flow and pressure are certainly related, but you are using them interchangeably which will get you in trouble.

be careful what you ask for ...

you can read the original Ziegler-Nichols paper here:

Mr. Driedger’s excellent website

and you might find this post helpful too:

previous thread with Ziegler-Nichols example

post #6 gives an example of the Ziegler-Nichols method applied to one type of PID control in an Allen-Bradley platform ... I’m not familiar with your type of controller so keep your eye on the units for the PID settings ... they may be different on your platform ...