Fuzzy Logic Poll, attempt 2

Looking for opinions on fuzzy logic.

Have you used it? Success of failure?
Would you use it if you had the chance?

re-posted to set up the poll

Maybe the "Master Pollster" kc9ih can help you out

Strange,

It worked in the practice posting area.

Why bother?

Fuzzy logic uses far more resources than a PID.
Do you know how to define the different classifications and rules?
What de-fuzzification rule would you use and why.

I have played with fuzzy logic. I see no benefit when I can do the same applications in more traditional ways that are more precise and less fuzzy.

I don't think fuzzy logic should be used on PLCs UNLESS there is a special card that actually does the fuzzy logic and has some sort of auto tuning.

There was a student name Ashwin that wrote a fuzzy logic program on a control logix. It didn't sound easy or fast. I would use a DSP.

The biggest problem with using fuzzy logic is finding people that know how to make it work. It is hard enough to find people that can program a PID.

Thanks Peter,

This was the type of thing I was looking for.
When I first learned about it, I found it to be easy conceptially. Just an extension to boolean logic that can deal with analog values.
Looking back on your comments, if you have to write the functions yourself, it can become complicated and I would normally not consider it for single input/single output functions that can be handled well by PID.

I am curious though, what is DSP?

Doug

Digital Signal Processor

Doug_Adam said:

I am curious though, what is DSP?
Doug

Click to expand...

A DSP is a digital signal processor. A DSP is very fast. Usually it has a couple of buses so an instruction and two data words can be fetched every clock cycle. DSPs also excel at doing multiply and adds and circular queues.

DSPs are not very good at doing character I/O and some have very few addressing modes.

The DSP sounds like a useful tool that I should familiarise myself with.
Do you have an example of any brands of DSP?
Are they like a PLC co-processor?

Doug_Adam said:

I am curious though, what is DSP?

Click to expand...

http://www.tech-encyclopedia.com/term/dsp_(digital_signal_processor)

http://www.google.com/search?hl=en&lr=&oi=defmore&q=define:Fuzzy+Logic


Doug, what's the application? "Fuzzy Logic" is a pretty vague catch-all term for a type of AI based on representations of what-ifs, maybes, and historical data.

One example (very simple one) of "fuzzy logic" and PLCs:

One person crosses through the door on an elevator, he/she weighs less then 30lbs. Three or four calls are registerd in the car. Hmm, that's strange, (this never happened before, or dosnt make sense); so automatically extinguish All the calls and hold the car with the doors open so that Mom might locate the lost kid.

This is one very simple example of how "fuzzy logic" might be use to compare old data to new data and make a seemingly intellegent decision, that wasnt really spicificly accounted for in the program. The above decision was based on an unusually light load, (less then 50 lbs) and an unusual amount of registered car calls for that load (more then one).

In my view, implimation of fuzzy logic within a typical PLC program, cant account for much more then a few real simple senerios.

I program DSPs, many people use DSPs but may not know it.

Doug_Adam said:

The DSP sounds like a useful tool that I should familiarise myself with.
Do you have an example of any brands of DSP?
Are they like a PLC co-processor?

Click to expand...

Yes, Rockwell's 1756-M02AE, 1756-M02AS and 1756-HYD02 motion controllers all use DSPs. I would bet most motion controller cards that fit in PLCs now are DSP based.

http://dspvillage.ti.com/docs/dspvi...IHomeTracking&HQS=Other+OT+home_p_dspoverview

Look at the technical area in the DSP resources. You have just entered the university of TI. If you want to know how drives work you should study these documents. TI wants to make it easy for people to design using their DSPs.

OK, I bookmarked your link. I think I'll take a bit of time to check these out.

Doug