use of fuzzy logic in system dynamics ?

[M/S Challenger Cargo Carriers p]

Please let me know any development in application of fuzzy logic in
system dynamics.

thanks

Ratan Saini
cccpl@del2.vsnl.net.in

[George Richardson]

On could argue that "fuzzy logic" is used in almost every model system
dynamicists build. Repeatedly, thinking about aggregates "smoothes out"
influences that for an individual would be shaped like a step, exactly the
way the membership function in a fuzzy set is a smothed out version of the
membership function in a discrete set. And the teaching of weighting
functions for aggregate if-thens has been going on in the field probably
longer than fuzy set logic has been popular.

But I dont know of a specific applications of fuzzy logic to accomplish
some end in a system dynamics model that required the sophisticated
accomplishments of the fuzzy logic folk.

...GPR

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George P. Richardson G.P.Richardson@Albany.edu
Rockefeller College of Public Affairs and Policy Phone: 518-442-3859
University at Albany - SUNY, Albany, NY 12222 Fax: 518-442-3398
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[rjrahn@microtec.net (R. Joel Rah]

George Richardson wrote...

>On could argue that "fuzzy logic" is used in almost every model system
>dynamicists build.

There is a fuzzy approximation theorem that says, essentially, that a TABLE
function is the same as a fuzzy decision rule. The basic idea is that an
input variable generates a fuzzy output. When you de-fuzzify the output (as
you have to do in fuzzy control systems), you get a (usually non-linear)
function. Now where have we seen that before....

R. Joel Rahn
rjrahn@pop.microtec.net