MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guía de usuario descargar pdf (Pagina 18)

1 Overview of S-Functions

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S-functions can be either single or multirate; a multirate S-function has

multiple sample times.

Sample times are specified in pairs in this format: [

sample_time,

offset_time

]. The valid sample time pairs are

[CONTINUOUS_SAMPLE_TIME, 0.0]

[CONTINUOUS_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]

[discrete_sample_time_period, offset]

[VARIABLE_SAMPLE_TIME, 0.0]

where

CONTINUOUS_SAMPLE_TIME = 0.0

FIXED_IN_MINOR_STEP_OFFSET = 1.0

VARIABLE_SAMPLE_TIME = -2.0

and the italics indicate a real v alue i s required .

Alternatively, y ou can specify that the sample time is inherit ed from the

driving b lock. In this case the S-function can have only one sample time pa ir

[INHERITED_SAMPLE_TIME, 0.0]

[INHERITED_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]

where

INHERITED_SAMPLE_TIME = -1.0

The following guidelines may help you specify sample times:

• A continuous S-function that changes during minor integration steps should

CONTINUOUS_SAMPLE_TIME, 0.0]sampletime.

•Acontinuous S-function thatdoesnot changeduring minor integrationsteps

should register the

[CONTINUOUS_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET] sample time.

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MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guía de usuario Pagina 18