www.pudn.com > chap1.rar > chap1_3plant.m

%S-function for continuous state equation 
function [sys,x0,str,ts]=s_function(t,x,u,flag) 
 
switch flag, 
%Initialization 
  case 0, 
    [sys,x0,str,ts]=mdlInitializeSizes; 
case 1, 
    sys=mdlDerivatives(t,x,u); 
%Outputs 
  case 3, 
    sys=mdlOutputs(t,x,u); 
%Unhandled flags 
  case {2, 4, 9 } 
    sys = []; 
%Unexpected flags 
  otherwise 
    error(['Unhandled flag = ',num2str(flag)]); 
end 
 
%mdlInitializeSizes 
function [sys,x0,str,ts]=mdlInitializeSizes 
sizes = simsizes; 
sizes.NumContStates  = 2; 
sizes.NumDiscStates  = 0; 
sizes.NumOutputs     = 1; 
sizes.NumInputs      = 1; 
sizes.DirFeedthrough = 0; 
sizes.NumSampleTimes = 0; 
 
sys=simsizes(sizes); 
x0=[0,0]; 
str=[]; 
ts=[]; 
 
function sys=mdlDerivatives(t,x,u) 
 
sys(1)=x(2); 
%sys(2)=-(25+5*sin(t))*x(2)+(133+10*sin(t))*u; 
sys(2)=-(25+10*rands(1))*x(2)+(133+30*rands(1))*u; 
 
function sys=mdlOutputs(t,x,u) 
 
sys(1)=x(1);