ST52T400 datasheet(27/94 Pages) STMICROELECTRONICS

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2.3.5 Input Membership Function.

ST FIVE allows the management of triangular

Mbfs. In order to define an Mbf, three different

types of data must be stored on the Program/Data

Memory:

the vertex of the Mbf: V;

the length of the left semi-base: LVD;

the length of the right semi-base: RVD;

In order to reduce the size of the memory area

and the computational effort the vertical dimension

of the vertex is set to 15 (4 bits).

By using the previous memorization method differ-

ent kinds of triangular Membership Functions may

be stored. Figure 4.6 illustrates a typical example

of Mbfs that can be defined in ST FIVE.

Each Mbf is then defined storing 3 bytes in the first

1 Kbyte of the program memory.

The Mbf is memorized by using the following

instruction:

MBF n_mbf lvd v rvd

where

n_mbf identifies Mbf, lvd, v, and rvd, which are the

parameters that describe the Mbf’s shape.

2.3.6 Output Singleton.

ST FIVE uses a particular kind of membership

function called Singleton for its output variables. A

Singleton doesn’t have a shape, like a traditional

Mbf, and is characterized by a single point identi-

fied by the couple (X, w), where the w is calcu-

lated by the Inference Unit as described before.

Often, a Singleton is simply identified with its Crisp

Value X.

2.3.7 Fuzzy Rules.

Rules can have the following structures:

if A op B op C...........then Z

if (A op B) op (C op D op E...)...........then Z

where op is one of the possible linguistic opera-

tors (AND/OR)

In the first case the rule operators are managed

sequentially; in the second one, the priority of the

operator is fixed by the brackets.

Each rule is codified by using an instruction set,

the inference time for a rule with 4 antecedents

and 1 consequent is about 3 microseconds.

Figure 2.10 Mbfs Parameters

LV D

R V D

I npu t M b f

O u t put S ingle t on

O u t put V a r ia b le

In p u t V ar iable

Figure 2.11 Example of valid Mbfs

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