Re: looking for defuzzification methods


Subject: Re: looking for defuzzification methods
From: Vladik Kreinovich (vladik@cs.utep.edu)
Date: Fri Apr 14 2000 - 16:37:27 MET DST


> Im searching for different defuzzification methods but in most of the
> books and reports I read, there`re only description of the standart
> methods "Maximum" and "Centroid".

You may also want to look at methods described in

J. Yen, N. Pfluger, and R. Langari, "A defuzzification
strategy for a fuzzy logic controller employing prohibitive
information in command formulation", Proceedings of IEEE
International Conference on Fuzzy Systems, San Diego, CA, March
1992.

J. Yen and N. Pfluger, Path planning and execution
using fuzzy logic, In: AIAA Guidance, Navigation and Control
Conference, New Orleans, LA, 1991, Vol. 3, pp. 1691-1698.

J. Yen and N. Pfluger, Designing an adaptive path
execution system, IEEE International Conference on Systems,
Man and Cybernetics, Charlottesville, VA, 1991.

These methods take care of the unfortunate situation when, e.g., to avoid an
obstacle, a car can either swerve to teh left or to the right. In this case, if the
situation is symmetric, centroid (and most other algorithm) would lead to the angle
0, and the car will run smack into the obtacle. John Yen and others therefore
recommend to check the value of the membership function for this proposed control,
and if it is too small (smaller than a threshold), divide the original membership
function graph into several connected zones in which the value was greater than the
threshold, and pick a centroid of the zone with the largest area.

If you have trouble getting copies of these papers, you can contact the author at
yen@cs.tamu.edu. If you are going to FUZZ-IEEE, you will meet him there: he is the
conference's General Chair.

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