
05927509
j
05927509
Huang, Li
Hu, Shikai
Li, Zhongfu
Determining membership functions by normalized universe of discourse.
J. Sichuan Univ., Nat. Sci. Ed. 47, No. 2, 207212 (2010).
2010
Sichuan University, Chengdu
ZH
fuzzy sets
membership functions
linguistic values
normalized universe of discourse
doi:10.3969/j.issn.04906756.2010.02.001
Summary: If we decide to use the technology based on fuzzy logic called fuzzy control, the first step is to determine the membership function of a linguistic value (a word), and then we can use a fuzzy set to represent the linguistic value (the word). However, until now there is no universal method to do this. In this paper, a new method to determine membership function is introduced, which is based on the normalized universe of discourse (NUOD). Instead of considering only one linguistic value, this method considers the membership functions of all the linguistic values we are interested in of a linguistic variable at the same time. First, the concept of normalized universe of discourse (NUOD) is introduced. The membership functions defined on NUOD are simple and easy to obtain. Second, using the information of the peak points of linguistic values, we determine the mapping from the universe of discourse (UOD) to the NUOD by interpolation or fitting. So we can determine the membership functions defined on UOD through the membership functions on NUOD.