ST52T400 datasheet(26/94 Pages) STMICROELECTRONICS

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ST52T400/T440/E440/T441

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2.3.3 Inference Phase.

The Inference Phase manages the alpha weights

obtained during the fuzzyfication phase to com-

pute the truth value (

Ω) for each rule.

This is a calculation of the maximum (for the OR

operator) and/or minimum (for the AND operator)

performed on alpha values according to the logical

connectives of fuzzy rules.

Several conditions may be linked together by lin-

guistic connectives AND/OR, NOT operator and

brackets.

The truth value

ω and the related output singleton-

move to the Defuzzyfication phase in order to

complete the inference calculation.

2.3.4 Defuzzyfication.

In this phase the output crisp values are deter-

mined by implementing the consequent part of the

rules.

Each consequent Singleton Xi is multiplied by its

weight values

i, calculated by the Fuzzy Infer-

ence Unit, in order to compute the upper part of

the defuzzification.

Each output value is deduced from the conse-

quent crisp values (Xi) by carrying out the follow-

ing defuzzification formula:

where:

i = 0,1 identifies the current output variable

N = number of the active rules on the current out-

put

ij =weight of the j-th singleton

Xij = abscissa of the j-th singleton

Fuzzy outputs are stored in the RAM location i-th

specified in the assembler instruction OUT i.

Figure 2.8 Fuzzyfication

Input 1

α1

Input 2

α2

OR = Max

IF INPUT 1 IS X1 OR INPUT 2 IS X2 THEN .......

Input 1

α1

Input 2

α2

IF INPUT 1 IS X1 AND INPUT 2 IS X2 THEN ......

Figure 2.9 Output Membership Functions

i-th OUTPUT

j-th Singleton

ij ωij

∑

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