MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guida Utente Scaricare il pdf (Pagina 38)

2 Writing S-Functions As M-Files

2-14

Example - Hybrid System S-Functions

Simulink includes a function called mixedm.m, which is an example of a hybrid

system (a combination of continuous and discrete states) modeled in an

S-function. Handling hybrid systems is fairly straightforward; the

flag

parameter forces the calls to the correct S-function subroutine for the

continuousand discrete parts ofthe system. One subtlety of hybrid S-functions

(or any multirate S-function) is that Simulink calls the

mdlUpdate, mdlOutput,

and

mdlGetTimeOfNextVarHit routines at all sample times. Thismeansthatin

these routines you must test to determine which sample hit is being processed

and only perform updates that correspond to that sample hit.

mixed.m models a continuous Integrator followed by a discrete Unit Delay. In

Simulink block diagram form, the model looks like this:

1 2 ... 33 34 35 36 37 38 39 40 41 42 43 ... 209 210

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MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guida Utente Pagina 38