Sigmoidal MF

Sigmoidal membership function

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Libraries:
Fuzzy Logic Toolbox / Membership Functions

Description

The Sigmoidal MF block implements a sigmoidal membership function.

$$f\left(x;a,c\right)=\frac{1}{1+e^{-a(x-c)}}$$

When the sign of a is positive, the curve increases from left to right. Conversely, when the sign of a is negative, the curve decreases from left to right. The parameter c sets the point of inflection for the curve.

This block is related to the Diff. Sigmoidal MF and Prod. Sigmoidal MF blocks.

Ports

Input

x — Input value

scalar | vector

Input value for which to compute membership values, specified as a scalar or vector.

Output

MF — Membership value

scalar | vector

Membership value, returned as a scalar or a vector. The dimensions of MF match the dimensions of x. Each element of MF is the membership value computed for the corresponding element of x.

Parameters

a — Transition area shape parameter

1 (default) | scalar

Parameter that controls the transition area shape. The magnitude of a controls the width of the transition area.

When the sign of a is positive, the curve increases from left to right. Conversely, when the sign of a is negative, the curve decreases from left to right.

Programmatic Use

Block Parameter: a

Type: string, character vector

Default: "1"

c — Transition area center

0 (default) | scalar

Transition area center.

Programmatic Use

Block Parameter: c

Type: string, character vector

Default: "0"

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

PLC Code Generation
Generate Structured Text code using Simulink® PLC Coder™.

Version History

Introduced before R2006a