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Pre

Breaks algebraic loops by an infinitesimal time delay

 

Description

Equations

Connections

Parameters

Modelica Standard Library

Description

This block delays the Boolean input by an infinitesimal time delay and therefore breaks algebraic loops. In a network of logical blocks, in every closed connection loop at least one logical block must have a delay because algebraic systems of Boolean equations are not practically solvable. The Pre block returns the value of the input signal from the last event iteration. Event iteration stops when both values are identical (u=preu).

Equations

y=preu

Connections

Name

Description

Modelica ID

u

Boolean input signal

u

y

Boolean output signal

y

Parameters

Name

Default

Units

Description

Modelica ID

preu0

false

 

Start value of pre(u) at initial time

pre_u_start

Modelica Standard Library

The component described in this topic is from the Modelica Standard Library. To view the original documentation, which includes author and copyright information, click here.

See Also

Boolean Signal Blocks

Signal Blocks