MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guide de l'utilisateur télécharger pdf (Page 40)

2 Writing S-Functions As M-Files

2-16

sizes.NumOutputs = 1;

sizes.NumInputs = 1;

sizes.DirFeedthrough = 0;

sizes.NumSampleTimes = 2;

sys = simsizes(sizes);

x0 = ones(2,1);

str = [];

ts = [0, 0 % sample time

dperiod, doffset];

% End of mdlInitializeSizes.

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

% mdlDerivatives

% Compute derivatives for continuous states.

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

function sys = mdlDerivatives(t,x,u)

sys = u;

% end of mdlDerivatives.

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

% mdlUpdate

% Handle discrete state updates, sample time hits, and major time

% step requirements.

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

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

% Next discrete state is output of the integrator.

% Return next discrete state if we have a sample hit within a

% tolerance of 1e-8. If we don't have a sample hit, return [] to

% indicate that the discrete state shouldn't change.

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

sys = x(1); % mdlUpdate is "latching" the value of the

% continuous state, x(1), thus introducing a delay.

else

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

end % matrix to indicate that the states have not

% changed.

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MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guide de l'utilisateur Page 40