WOLFRAM SYSTEMMODELER

Pre

Breaks algebraic loops by an infinitesimal small time delay (y = pre(u): event iteration continues until u = pre(u))

Wolfram Language

In[1]:=
SystemModel["Modelica.Blocks.Logical.Pre"]
Out[1]:=

Information

This information is part of the Modelica Standard Library maintained by the Modelica Association.

This block delays the Boolean input by an infinitesimal small 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, since algebraic systems of Boolean equations are not solvable.

The "Pre" block returns the value of the "input" signal from the last "event iteration". The "event iteration" stops, once both values are identical (u = pre(u)).

Parameters (1)

pre_u_start

Value: false

Type: Boolean

Description: Start value of pre(u) at initial time

Connectors (2)

u

Type: BooleanInput

Description: Connector of Boolean input signal

y

Type: BooleanOutput

Description: Connector of Boolean output signal

Used in Examples (1)

LogicalNetwork1

Modelica.Blocks.Examples

Demonstrates the usage of logical blocks

Used in Components (3)

RSFlipFlop

Modelica.Blocks.Logical

A basic RS Flip Flop

ThyristorBridge2mPulse

Modelica.Electrical.PowerConverters.ACDC

2*m pulse thyristor rectifier bridge

HalfControlledBridge2mPulse

Modelica.Electrical.PowerConverters.ACDC

2*m pulse half controlled rectifier bridge