Control Logix

Can control Logix be made to perform intergal functions?

Yes.

Now here is a question for you. What does the 'I' in PID stand for?

Fuzzy

HI!

I know i was like what was i thinking. Well actually I thought PID took care more on the process values side..ofcouse integral but then..taking care of minimizing errors and that kind of stuff.

I need to find out if we can perform complex mathematics using Control Logix. My thesis is on Fuzzy applications using the RS logix 5000 using Function Block. I was just keen to find out if we could perform the Mean of maxima and centre of area applications and if someone had already done it .

Ashwin.

Numerical integration is usually uses only the basic arithmatic functions so I wouldn't see why not?... The trick with numerical integration is usually getting the process to start properly, picking the proper time step and accounting for all the terms.

Do you have any background in numerical integration?

Numerical Integration

No, Just what I did in course work as far as Numerical Integration goes. Since my thesis is going to be more on the working project, i was curious if and when i get to the defuzzification part, will it be possible to build a function block to perfrom them

One could do numerical integration on any PLC platform although in some you are limited to integer math.

The classic iterative method for integration is Simpson's rule. I'm sure you can find a ton of references to it.

???? Fuzzy thinking ?????

Are you asking the right questions?

One does not need a integrate function or use numberical methods to do a centroid function unless polynomials, sines or sine^2 are used to specify the regions for fuzzifying and de fuzzifying. If you use simple trigangles, trapezoids and rectanges then this is easy and faster. Using numerical integration will slow the PLC down to a crawl. I have plenty of source code on how this is done. See high school geometry book. There is plenty of code on the internet.

The big question is why? What are you trying to do in the end? A plc is not a good platform for writing fuzzy logic code. Do you expect people to use this Fuzzy Logic block? What would this Fuzzy Logic block be good for besides wasting CPU time?

I have seen the Omron fuzzy logic module work. It work well but it is its own module with its own CPU I am pretty sure is has a separate program to download the rules, it was long ago. How do you plan to download the rules? Are you going to write a HMI just for that function block? If so, I can tell you that writing the Fuzzy Logic block will be easy compared to doing the HMI.

If this is for a college project, what new ground are you trying to explore? There must be more that just be the first person to implement fuzzy logic in a PLC. How will this advance the field of Fuzzy Logic? I think it will only show that it can be done, but should shouldn't have tried.

Just because you can does not mean you should.

I would prove that it can be down economically on a small micro or DSP that could be made into a fuzzy logic card for those PLC manufacturers that don't have one.

What Omron able to give theirs away? Could anyone make it go? I am sure some people could but the market is limited in how many applications require fuzzy logic and how many people can make the rules. That is why people stay with the devil they ( don't) know. ( PID ).

Get a TI DSP starter kit. On the TI website they have an app note, with code' on how to implement a fuzzy logic controller. The application compares a fuzzy logic implementation with a PID implentation on a servo motor.

I have broken my rule about asking questions again.

Problem

Hey!

The reason for this thread to be born is becoz my thesis is on this area. Surely it has been done before..AB Flex is a good example. Well my advisor felt its a good place to do some credible work..What I intened doing? I am trying to develop a general fuzzy controller to implement fuzzy applications using the COntrol logix..ofcouse intern using RS logix 5000 and RS view. THe problem would be that of the inverted pendulum..I am trying to still figure out my direction so yes...as u said rightly i am not asking the right questions..I hope as time passes I will. surely with the help i am able to find here on this site!