analogue defuzzifier
Wed, 23 Oct 1996 15:21:18 +0100


Is there anybody that knows of an analogue defuzzifying circuit,
that could be used in a totally analogue, non uP Fuzzy System?

Up till now I've designed a fuzzifier and the inference part.
This is easy to build when you want the system to operate
according to the MIN/MAX method.
For every fuzzy set I now create a voltage, ranging from
approximately -10 volts to +10 volts, where 0 volts indicate 100%
membership. This circuitry is primarily intended for triangular
membership functions.
Now I'm kind of breaking my head over the defuzzifying circuit.
The rulebase concludes that the output of the controller must be
30 % medium and 70% high, how to translate this into an output
value? When one is using computers, this is a simple task, it only
involves a little math, but how to do it with "some OpAmps, a few
BJT's etc."?
I guess some multiplying or integrating elements must be inserted.

>From the basic principles of Fuzzy Logic, I think an analogue
controller is a good way to ensure total fuzziness.
It might not be easy to build, especially when the number of
inputs and outputs of the system increases.

This system is intended to serve as illustrative material in
a course on FL for BSc students electrical engineering, and would
give a pretty good idea what fuzzy is all about.

Is there anybody that struggled with the same problem, is it
perhaps much simpler then I think?

Thanks in advance for any replies,


E.W. Buhler, dpt. Electrical Engineering

University of the Netherlands Antilles
Jan Noorduynweg 111
Curacao, Dutch Carribean

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