MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Podręcznik Użytkownika Pobierz pdf (Strona 41)

Examples of M-File S-Functions

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% End of mdlUpdate.

%==============================================================

% mdlOutputs

% Return the output vector for the S-function.

%==============================================================

function sys = mdlOutputs(t,x,u,doffset,dperiod)

% Return output of the unit delay if we have a

% sample hit within a tolerance of 1e-8. If we

% don't have a sample hit then return [] indicating

% that the output shouldn't change.

if abs(round((t-doffset)/dperiod)-(t-doffset)/dperiod) < 1e-8

sys = x(2);

else

sys = []; % This is not a sample hit, so return an empty

end % matrix to indicate that the output has not changed

% End of mdlOutputs.

Example - Variable Step S-Functions

This M-file is an example of an S-function that uses a variable step time. This

example, in an M-file called

vsfunc.m, calls mdlGetTimeOfNextVarHit when

flag = 4. Because the calcula tion of a next sample time depends on the input

u, this block has direct feedthrough. Generally, all blocks that use the input to

calculate the next sample time (

flag = 4) require direct feedthrough. Here is

the code for the M-file S-function:

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MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Podręcznik Użytkownika Strona 41