Today is...
Sunday, September 15, 2019
Welcome to Control.com, the global online
community of automation professionals.
Featured Video...
Featured Video
A demonstration of EtherCAT control of linear motors using the CTC EtherCAT master.
Our Advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive
PID Parameters
Need help setting PID parameters for a water cooling loop

Hi everyone,

In my role, I am typically asked to provide a control narrative for a given process while PLC programming and PID loop settings are configured by another contractor. In this case, I have been asked to include configuration information in the narrative. It needs to be enough to start the plant. Fine tuning can be done by the commissioning team.

Can you guys recommend a software where I can simulate a fairly simple system, which I will describe below? I am looking to advance my knowledge of PLC programming and don't mind spending money on software or hardware. The PLC in this particular case is an Allan Bradley RSLogix 5000. I would like to enter the parameters of particular equipment and end up with a tuned PID loop.

System:
We are cooling crude coming from ~50C to 32C via a series of shell tube heat exchangers. On the shell side we have a closed loop glycol system. The glycol removes heat from crude and is then cooled by a series of air coolers. Desired temperature is achieved by turning on and off fans. There are a total of 52.. Fairly straight forward.

Should I be looking at purchasing RSLogix 5000 Studio? Will it be able to simulate the plant and tune the loop? Is there other software I can use to get going?

Really appreciate all of your help!

Depends on what do you mean by simple!

Temp control with long transport delays can be simple or complex. It all depends on the control objectives, precision, etc. and how much funding is available.

It is not a question with a simple, postable answer.

I'm surprised that no A-B/Rockwell guys have jumped in yet.

I know Rockwell has a "Partner" that sells the Loop-Pro Tuner software.
https://controlstation.com/rockwell-tuner/
The partners generally do stuff Rockwell doesn't, so I doubt that Rockwell's standard development software includes Loop tuning.

This site
https://onlineplcsupport.com/rslogix-5000-pid-tuning
shows a means of watching the loop response trend by varying tuning constants with some trick settings in RSLogix 5000. But I could not catch how he defined the process characteristics (gain, time constant and delay) which is sort of fundamental

There's a freebie Excel spreadsheet PID simulator that uses the "parallel" PID algorithm at this link.
http://www.engineers-excel.com/Apps/PID_Simulator/Description.htm
I don't know whether A-B uses parallel or ideal algorithm.

Google will find a variety PID loop simulation software.