In addition, the following rule base is implemented in the system (Figure 2):
RUL1: "IF B1=vt AND B2=vt AND B3=pf AND B4=pf AND B5=vf TO A1=vt "
RUL2: "IF B1=rf AND B2=rf AND B3=vt AND B4=vf AND B5=vt TO A2=vt "
RUL3: "IF B1=pt AND B2=vt AND B3=vf AND B4=rt AND B5=pt Maintenance A3=vt "
RUL4: "IF B1=vt AND B2=vt AND B3=vt AND B4=vt AND B5=vt TO A1=pf »
RUL5 : "IF B1=vt AND B2=vt AND B3=vt AND B4=vt AND B5=vt TO A2=rt "
RUL6: "IF B1=pt. AND B2_=pt. AND B3=pt. AND B4=pt. AND B5=pt. Maintenance A3=pt. "
RUL7: "IF B1=pt. AND B2_=pt AND B3=pt AND B4=pt AND B5=pt TO A1=rt "
RUL8: "IF B1=pt AND B2_=pt AND B3=pt AND B4=pt AND B5=pt TO A2=pt "
RUL9 : "IF B1=vt AND B2=vt AND B3=vt AND B4=vt AND B5=vt Maintenance A3=rt "
Consider the case when a message containing B2=rt. Since there was no information about the presence of other symptoms, then B1=un, B3_=un, B4_=un , B5_=un. Therefore, we can consider only that part of the rules in which B2=rt.
On fig. Figures 3-6 show fuzzy inference surfaces for assessing defect cases for fuzzy models A1, A2, A3. At the first stage, the input values (ie B2 values) are compared with the rule base implemented in the system. This comparison is equivalent to the operation of intersection of fuzzy sets. Based on this comparison, a modified membership function for A1, A2 and A3 is determined in accordance with each of the rules. Further, to find the generalized membership functions A1, A2 and A3, the operation of combining fuzzy sets is applied. After finding the generalized membership functions A1, A2 and A3, the centroid method determines the quantitative values of A1, A2 and A3 , the largest of which (in this case A1 ) will correspond to the type of defect in the system (i.e. D1 ).[13]
Fig. 1. Graph of membership functions of linguistic variables.
Fig. 2. Rules of fuzzy knowledge bases of fuzzy logical models.
Fig. 3 Fragments of computational experiments.
Fig.4 Fuzzy inference surface for case A1.
Fig. 5 Fuzzy inference surface for case A2. Fig.6 Fuzzy inference surface for case A3. Conclusions Thus, the increasing requirements for the reliability of data transmission networks necessitate the creation and implementation of promising methods and diagnostic tools. The given technique for estimating the classes of states of alleged defects in a data transmission network under conditions of incomplete information allows us to successfully solve the problem of diagnosing data transmission networks by applying the apparatus of fuzzy set theory.
Analytical expressions that determine the characteristics of fuzzy set elements for a data transmission network and the rules for making a decision about the type of defect, as well as methods for constructing membership functions of fuzzy sets and implementing rule bases, are the basis for building a system for diagnosing data transmission networks based on fuzzy set theory.
The use of the apparatus of fuzzy set theory makes it possible to create fairly simple diagnostic algorithms based on expert knowledge, taking into account both the objective characteristics of data transmission networks and the subjective states of service personnel, which is not possible using traditional diagnostic methods and algorithms.[6]
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