S7-300

[andrzejac]

Hello!

I've got a problem with fb41 "CONT_C". I'm writing

parent task​

about PID regulator with great time delay. I don't know how simulate an inertial object of first range with time delay on FB41.
Somebody knows how to do that??
I'll be very thankful for help.
Sorry for my english. .

 

[dchartier]

Hello Andrzejac;

You speak about FB41, a continuous control PID function on the S7-300, on one hand, and about control of a "First-Order plus Dead Time" process on the other hand.
These are 2 different problems.

Setting up the Step 7 FB41 is pretty well explained in different Siemens manuals (for example, Standard and System Functions, SFB41) and has been discussed many times on this forum; a search on the forum on FB41 should bring out many posts that could enlighten you, or ask specific questions about your programming problems and maybe we can help.

Now, selection of the different gains to control a FODT process with a PID loop is a totally different beast. Luckily, we have a few experts on hand (like Peter Nachtwey), and students who are learning with the masters (such as Pandiani). Here are links to some of their discussions, could be interesting for you.They certainly were for me.

http://www.plctalk.net/qanda/showthread.php?t=27057

http://www.plctalk.net/qanda/showthread.php?t=26395

http://www.plctalk.net/qanda/showthread.php?t=25351

http://www.plctalk.net/qanda/showthread.php?t=25331

If the postings above help you out, here is a link to a site that discusses all forms of advanced control issues. Peter Nachtwey is also a frequent contributor there; I can only recommend it:

http://www.controlguru.com/

Hope this helps,
Daniel Chartier

 

[andrzejac]

Thanks for your help Daniel, but it's too much for me to overlook that and i don't have a lot of time .

On next week at the latest i must apply my parent task.So... .
I'm sending my project. If somebody could peek on this and possibly correct my stakes.

This is Siemens Simatic Step 7 V5.2 version, and ProTool/Pro V6.0.

Thanks so much for help.
Andrzej

 

[andrzejac]

Hello.

I have recently written about my problem with simulation the inertial object of first range with time delay. Unfortunately, nobody didn't knew how to do that. I've got some hints, but i don't know how to model that in Step7.
So...
An object of first range with time delay we can model by the serial
connection an inertial object of first range and object with clean delaying, that we can model on PLC as a sliding record with specifed length as that amount of his cells multiply by the value of sampling time was equaled time delay.

I will be gratteful for help.

Andrzej.

 

[andrzejac]

Nobody konows how to do this?? Please help me. It's really important for me.

 

[kamenges]

It sounds like you already know what you need to do. For a first approximation a delay array followed by a first order filter possibly followed by an integrator should give you what you want.

Do you have a specific question on how to do something? Questions like 'How do I build a model' are hard for a forum to answer well.

Keith

 

[andrzejac]

Hello!

Is it normal that LMN_PER in FB41 has value 27648 or sth??

 

[andrzejac]

Hello!

How to simulate an object of first order time-delay in Siemens Simatic Step7. (SFB41 CONT_C)

Thanks for help.

 

[andrzejac]

Hello.

I need somebody who know very well Siemens Simatic Step7. I need to write a program in SCL which will FOPDT. Then this program will be simulated on PID Control SFB41.

Can somebody help me??

I'll be very grateful for help.