function [sys,x0,str,ts,simStateCompliance] = int_hyo(t,x,u,flag)

  switch flag,

      case 0,

          [sys,x0,str,ts,simStateCompliance]=mdlInitializeSizes;

      case 1,

          sys=mdlDerivatives(t,x,u);

      case 2,

          sys=mdlUpdate(t,x,u);

      case 3,

         sys=mdlOutputs(t,x,u);

     case 4,

         sys=mdlGetTimeOfNextVarHit(t,x,u);

     case 9,

         sys=mdlTerminate(t,x,u);

     otherwise

        DAStudio.error('Simulink:blocks:unhandledFlag', num2str(flag));

 end

 function [sys,x0,str,ts,simStateCompliance]=mdlInitializeSizes

 sizes = simsizes;

 sizes.NumContStates  = 1;

 sizes.NumDiscStates  = 0;

 sizes.NumOutputs     = 1;

 sizes.NumInputs      = 1;

 sizes.DirFeedthrough = 0;

 sizes.NumSampleTimes = 1;   % at least one sample time is needed

 sys = simsizes(sizes);

 x0  = [-1]; %之前这里是0，改为1，应为x0代表-cos（t）在0初始时刻应该为-1

 str = [];

 ts  = [0 0];

 simStateCompliance = 'UnknownSimState';

 function sys=mdlDerivatives(t,x,u)

 sys = u;

 function sys=mdlUpdate(t,x,u)

 sys=[];

 function sys=mdlOutputs(t,x,u)

 sys=x ;

 function sys=mdlGetTimeOfNextVarHit(t,x,u)

 sampleTime = 1;    %  Example, set the next hit to be one second later.

 sys = t + sampleTime;

 function sys=mdlTerminate(t,x,u)

 sys = [];

function sys=mdlDerivatives(t,x,u)

J=2;

dt=sin(t);

ut=u(1);

sys(1)=x(2);

sys(2)=1/J*(ut+dt);             //注:  1/J*(ut+dt)为一个二阶导函数

function sys=mdlOutputs(t,x,u)

sys(1)=x(1);

sys(2)=x(2);