MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guia do Utilizador descarregar pdf (Página 113)

Examples of C MEX-File S-Function Blocks

3-69

during the simulation. In the transfer function used in this example, the

parameters of the transfer function vary with time.

The output of

vsfunc is simply the input u delayed by a variable amount of

time.

mdlOutputs sets the output y equal to state x. mdlUpdate sets the state

vector

x equal to u, the input vector. This example calls

mdlGetTimeOfNextVarHit, an S-function routine that calculates and sets the

“time of next hit,” that is, the time when is

vsfunc is next called. In

mdlGetTimeOfNextVarHit themacrossGetU is used togetapointerto theinput

u. Then this call is made:

ssSetTNext(S, ssGetT(S)(*u[1]));

The macro ssGetT gets the simulation time t. T he second input to the block,

(

*u[1]),isaddedtot, andthe macrossSetTNext setsthetimeofnexthitequal

t+(*u[1]), delaying the output by the amount of time set in (*u[1]).

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MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guia do Utilizador Página 113