function [sys,x0,str,ts]=s_function(t,x,u,flag)
switch flag,
case 0,
    [sys,x0,str,ts]=mdlInitializeSizes;
case 1,
    sys=mdlDerivatives(t,x,u);
case 3,
    sys=mdlOutputs(t,x,u);
case {2, 4, 9 }
    sys = [];
otherwise
    error(['Unhandled flag = ',num2str(flag)]);
end
function [sys,x0,str,ts]=mdlInitializeSizes
sizes = simsizes;
sizes.NumContStates  = 2;
sizes.NumDiscStates  = 0;
sizes.NumOutputs     = 2;
sizes.NumInputs      = 1;
sizes.DirFeedthrough = 0;
sizes.NumSampleTimes = 0;
sys=simsizes(sizes);
x0=[pi/10,0];
str=[];
ts=[];
function sys=mdlDerivatives(t,x,u)
g=9.8;
m=2.0;
M=8.0;
l=0.5;
a=l/(m+M);

S=4/3*l-a*m*l*(cos(x(1)))^2;
fx=g*sin(x(1))-a*m*l*x(2)^2*sin(2*x(1))/2;
fx=fx/S;
gx=-a*cos(x(1));
gx=gx/S;

sys(1)=x(2);
sys(2)=fx+gx*u;
function sys=mdlOutputs(t,x,u)
sys(1)=x(1);
sys(2)=x(2);