Hi Candyengineer,

I tried to read about Fuzzy Logic before but I would say I couldn't get something useful out of my little reading but I will just tell you what I thought about Fuzzy Logic.
When I searched other forums in the past (didn't search Siemens forum), I could see that the ones who were interested in Fuzzy were either college students who were making their graduation projects or ones who askpreliminary questions about Fuzzy but I didn't find someone talking about fuzzy logic in process automation and how far it's helpful and effective.

Fuzzy logic is based on IF THEN.
It's about how far you can have IF(conditions) and how you can combine these IF(conditions) together and get the result that you want.
My main concerns were about PID closed loops, I didn't study Fuzzy Logic in college but some of my colleagues were talking about Fuzzy Logic controland were saying it's better than PID control and it's just a matter of time and fuzzy logic will replace PIDin all non-linear systems.
But after my poor search and mylittle understandingI just came to a point that PID controllers will still dominate and Fuzzy logic is not to replace them but to improve them in very special cases.
As I told you Fuzzy is made of some IF THEN so I'll take an example of flow control loop.
A flow meter and ball control valve.
The ball control valve is a non-linear control valve which means the amount of flow is not directly proportional to the valve's opening position.
Such a loop can be controlled by a PID controller.
Another alternative is to obtain the valve characteristic curve and study it well and understand how the valve reacts to output signal then give it a time and write IFTHEN statementsaccording to the curve to get the required valve position.
Then another IF THEN for corrective action (Increase position & Decrease position)in case you have some drifts in valve's position.
If you have another 2 loops and you want to interlock these loops together, then I believe you will spend a long time to solve such a problem with IF THEN.

It would be like having a big truth tablereplacinganalog processing and mathematical equations.

I think fuzzy is not going to replacePIDspecially if you have many PID loops in a system. I mean if I have 800 PID loops, I will never think of using Fuzzy Logic.
However, Fuzzy logic can be used in a verynon linearsystem that can be characterized. What I mean by characterized is Action/Response characteristics.
If I were you, I would chose a system with many variables and which you can easily get characteristic for.
Afterobtaining characteristic start implementing your programming.

One thing I couldn't get an answer for was what the difference is between any language and FPL (fuzzy programming language).

I mean you can write IF THEN and combine them with many IF THEN as much as you can in LAD,STL or SCL.

I'm really wishing you luck in your project and wish if you will keep us informed with your results and your thoughts about Fuzzy Logic in real life applications.

I really wish if you or anyone tell me about his experience with Fuzzy Logic and correct my understanding.

I think you will have to read this manual deeply. It's very simple and helpful.

I tried to attach a file I gotfrom Rockwell automation which also describes Fuzzy Logic and its implementation is some real applications but the file size is more than 2 MB.

If you are interested, please drop me a private message with your email address so I can send it to you.

Best regards.