Increasingly, research in the field of fuzzy theory is focusing on fuzzy sets (FSs) whose membership functions are themselves fuzzy. The key concept of such type-2 FSs is the footprint of uncertainty. It provides an extra mathematical dimension that equips type-2 fuzzy logic systems (FLSs) with the potential to outperform conventional (type-1) FLSs. While a type-2 FLS has the capability to model more complex relationships, the output of a type-2 fuzzy inference engine is a type-2 FS that needs to be type-reduced before defuzzification can be performed. Unfortunately, type-reduction is usually achieved using the computationally intensive Karnik-Mendel iterative algorithm. In order for type-2 FLSs to be useful for real-time applications, the computational burden of type-reduction needs to be relieved. This work aims at designing computationally efficient type-reducers using a genetic algorithm (GA). The proposed type-reducer is based on the concept known as equivalent type-1 FSs (ET1FSs), a collection of type-1 FSs that replicates the input-output relationship of a type-2 FLS. By replacing a type-2 FS with a collection of ET1FSs, the type-reduction process then simplifies to deciding which ET1FS to employ in a particular situation. The strategy for selecting the ET1FS is evolved by a GA. Results are presented to demonstrate that the proposed type-reducing algorithm has lower computational cost and may provide better performance than FLSs that employ existing type-reducers.
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Tan, WW., Wu, D. (2007). Design of Type-Reduction Strategies for Type-2 Fuzzy Logic Systems using Genetic Algorithms. In: Jain, L.C., Palade, V., Srinivasan, D. (eds) Advances in Evolutionary Computing for System Design. Studies in Computational Intelligence, vol 66. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-72377-6_7
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