function [sys,x0,str,ts] = spacemodel(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)]);endfunction [sys,x0,str,ts]=mdlInitializeSizessizes = simsizes;sizes.NumContStates  = 2;sizes.NumDiscStates  = 0;sizes.NumOutputs     = 1;sizes.NumInputs      = 1;sizes.DirFeedthrough = 1;sizes.NumSampleTimes = 1;sys = simsizes(sizes);x0  = [0;0];str = [];ts  = [0 0];function sys=mdlDerivatives(t,x,u)M=1;if M==1    a=1+4*abs(sin(2*pi*t));    b=20+10*abs(sin(2*pi*t));    k=1+9*abs(sin(2*pi*t));elseif M==2    a=5;    b=30;    k=1;end    ut=u(1);sys(1)=x(2);sys(2)=-(a+b)*x(2)-a*b*x(1)+k*ut;function sys=mdlOutputs(t,x,u)sys(1)=x(1);