ST52T430 datasheet(41/88 Pages) STMICROELECTRONICS

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7 FUZZY COMPUTATION (DP)

The ST52T430/E430 Decision Processor (DP)

main features are:

Up to 8 Inputs with 8-bit resolution;

1 Kbyte of Program/Data Memory available to

store more than 300 to Membership Functions

(Mbfs) for each Input;

Up to 128 Outputs with 8-bit resolution;

Possibility of processing fuzzy rules with an

UNLIMITED number of antecedents;

UNLIMITED number of Rules and Fuzzy Blocks.

The limits on the number of Fuzzy Rules and

Fuzzy program blocks are only related to the

Program/Data Memory size.

7.1 Fuzzy Inference

The block diagram shown in Figure 7.1 describes

the different steps performed during a Fuzzy

algorithm. The ST52T430/E430 Core allows for the

implementation of a Mamdani type fuzzy inference

with crisp consequents. Inputs for fuzzy inference

are stored in 8 dedicated Fuzzy input registers.

The LDFR instruction is used to set the Input Fuzzy

registers with values stored in the Register File.

The result of a Fuzzy inference is stored directly in

a location of the Register File.

7.2 Fuzzyfication Phase

In this phase the intersection (alpha weight)

between the input values and the related Mbfs

(Figure 7.2) is performed.

Eight Fuzzy Input registers are available for Fuzzy

inferences.

Figure 7.1 Fuzzy Inference

Figure 7.2 Alpha Weight Calculation

After loading the input values by using the LDFR

assembler instruction, the user can start the fuzzy

inference

using

the

FUZZY

assembler

instruction. During fuzzyfication: input data is

transformed in the activation level (alpha weight) of

the Mbf’s.

7.3 Inference Phase

The Inference Phase manages the alpha weights

obtained during the fuzzyfication phase to compute

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

linguistic connectives AND/OR, NOT operators

and brackets.

The truth value

ω and the related output singleton

are used by the Defuzzyfication phase, in order

to complete the inference calculation.

FUZZYFICATION

INFERENCE

PHASE

DEFUZZYFICATION

N rules

N rules -1

Input Values

Output Values

αij

j-th Mbf

i-th INPUT VARIABLE

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