S function疑问，sizes.NumSampleTimes疑问

zhuchao12345

function [sys,x0,str,ts] = zhu(t,x,u,flag)
switch flag
  case 0
    [sys,x0,str,ts]=mdlInitializeSizes;
  case 3
    sys=mdlOutputs(t,x,u);
  case {1,2,4,9}
    sys=[];
  otherwise
    error(['Unhandled flag = ',num2str(flag)]);

end

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


sizes = simsizes;

sizes.NumContStates  = 0;
sizes.NumDiscStates  = 0;
sizes.NumOutputs     = 1;
sizes.NumInputs      = 1;
sizes.DirFeedthrough = 1;
sizes.NumSampleTimes = 0;   % at least one sample time is needed

sys = simsizes(sizes);

%
% initialize the initial conditions
%
x0  = [];

%
% str is always an empty matrix
%
str = [];

%
% initialize the array of sample times
%
ts  = [0 0];

% end mdlInitializeSizes

%=============================================================================
% mdlOutputs
% Return the block outputs.
%=============================================================================
%
function sys=mdlOutputs(t,x,u)

sys = 0.25*pi*0.0171*8*10^6*(0.027/(0.027-0.25*pi*0.0171*u))^1.2;

% end mdlOutputs
为什么我将sizes.NumSampleTimes =1;改为sizes.NumSampleTimes = 0;就会报错Sample times (TS) matrix returned by M-File S-function 'zhu' in 'untitled/S-Function' must be empty，请各位高手指点一二