fuzzy logic controller design

[Basile21]

Hi,

I'm using DSC module and I have problem with the "Fuzzy logic Controller Design" so I used 3 antecedences and when I clicked on consequence I can't add term over 9 .

And the theorie say's that when we have 3 antecedences  you must have 27 rules.

[corys]

I think either you're confused with your terms, or I'm confused with what you are trying to do. Consequences (which if I remember correctly are limited to 9 in the fuzzy logic toolkit) are different from rules. The rules are the "if-then" statements for determining the consequence(s) to use. The number of rules required is determined by the number of variables used (and the number of terms for each variable), but this is unrelated to the number of consequences you decide to use / need.

[Basile21]

Hi Cory,

Thanks for your help, but I sure that when you use 3 variables with triangle you will have 27 rules in fuzzy logic, and for 27 rules you must have 27 consequences in the Fuzzy logic Controller Design and yhe problem with this controller is we are limited to 9  .

[corys]

What is it you're trying to do? Are you sure you need 27 consequences, or are you trying to make 27 consequences solely because you have 27 rules? I ask, because maybe you don't need as many consequences as you may think. A fuzzy logic controller that maintains a steady speed for a motor, for instance, may only need 3 consequences (speed up, slow down, or stay steady). There may be 20+ rules to determine which consequences to use, and with what weight, which is part of what makes the fuzzy logic controllers so useful. Rather than defining a specific consequence per rule, you can create a smooth spectrum of outputs based on a limited amount of consequences / programming. If you do need 27 consequences, then it looks like using the FL toolkit may be an issue. Maybe if you can provide some more information, we can help you in figuring out a different method of going accomplishing your goals, whether it be creating a FL controller without the toolkit, or taking a new approach.

[Basile21]

Hi Cory,

In my application I have 3 parameters like measures (Input of the fuzzy logic controller) and 1 parameter a command (the output of the fuzzy logic controller) and when I established my rules I need to have 27 rules imperatively. I can use only 9 rules but it will not be as precise as the reality.

[corys]

I assume you have 3 terms for each of your 3 parameters then, to get the 27 rules. If this is the case, going to the rule-base editor will bring up all 27 rules (the control designer automatically populates the rules list, so you don't even have to add additional rules to reach this number). Consequences, unlike rules however, are limited to 9. When I asked what you are using the controller before, perhaps I should have been more specific, as I was more curious as to whether or not you need singletons for your consequences? I am still having trouble imagining a situation where you need 27 *consequences*, unless perhaps they are singletons.

That being said, I don't know of a way to use the fuzzy logic kit to create a controller with more than 9 consequences (27 rules are no problem). How familiar are you with the mathematics and principles behind the fuzzy logic controller? It's always possible to write your own code, and if you need any help, I'd be more than willing to help out.

[Bruno_Cesar]

Hello all

The PID and Fuzzy Logic Toolkit 2009 was completely redesigned.

There are new API VIs and a more intuitive user interface for creating controllers.

You can create MIMO controllers with unlimited inputs and outputs, and also modify the controller on-the-fly.

Check it out the new features and let us know your needs on Fuzzy control.

LabVIEW PID and Fuzzy Logic Toolkit User Manual

Regards,

Bruno Cesar

National Instruments