我有一个问题，关于把一个PID控制器在我的simulink文件。
在我的simulink文件中，我使用pid控制器来控制我的过程。我使用s函数作为我的流程框图。
根据Ziegler-Nichols方法，对于第一步，我们将k设置为最小值（0.5），因此我将0.5放入我的比例值。但有无控制器的结果并没有什么不同，即使我增加或减少比例值。
为什么会出现这个问题？希望有人能帮助我。2谢谢。
我的框图看起来像下面的图片.参考这张图片
http://s1009.photobucket.com/albums/af218/syarinazulkifeli/?action=view&current=Untitled-1.png
下面是我的s-function文件：

function [sys,x0,str,ts]= reactor_sfcn(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 9
    sys =[];
end

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

s = simsizes;
s.NumContStates   = 11;
s.NumDiscStates   = 0;
s.NumOutputs      = 11;
s.NumInputs       = 1;
s.DirFeedthrough  = 0;
s.NumSampleTimes  = 1;

sys = simsizes(s) ;
x0 = [0.0258,0,0,0,0,0,0,0,8.83,303.15,303.15];
str=[] ; 
ts = [0 0];

    function sys = mdlDerivatives (t,x,u)
Tjo = u;
sys = reactor(t,x,Tjo);

        function sys = mdlOutputs(t,x,u)
%                 sys(1)=x(1);
%                 sys(2)=x(2);
%                 sys(3)=x(3);
%                 sys(4)=x(4);
%                 sys(5)=x(5);
%                 sys(6)=x(6);
%                 sys(7)=x(7);
%                 sys(8)=x(8);
%                 sys(9)=x(9);
%                sys(10)=x(10);
%                sys(11)=x(11);
                 sys = x;

s函数文件的链接

function DXDT = reactor(t,x,Tjo)

% -------------------------------------------- %
%       Parameters definition
% -------------------------------------------- %  
I  = x(1);   X = x(2);   P0 = x(3);  
P1 = x(4);  P2 = x(5);   Q0 = x(6);  
Q1 = x(7);  Q2 = x(8);    M = x(9);
Tjo = x(10);  T = x(11); 

% ---------------------------------------
%               Constants
% =======================================

%constant
 M0 = 8.83;
 I0 = 0.0258;
 Qh = 60.44;
 MMWm = 100.3;
 U0 = 55.1;

% Densities
dp = 1200;                
dm = 968-1.225*(T-273.15);               
Rhoc = 998;                            

% volume expansion factor
Fev = (dm - dp)./dp ;                  

% volume fraction
 Fvm = (1 - X)./(1 + Fev*X);           
 Fvp = X*(1-Fev)./(1+Fev*X);

% Total reactant mixture density
 Rho = dm*Fvm + dp*Fvp;            
% Reactor and jacket volume
 Vc = 2;                            
  V = 2;                           
% Reactor dimension      
At =3.1416*0.15*0.113;    
% coolant flow rate
Mc = 0.41/18;                      
%   
 Cpc = 77.22;            
 Cp = 199.13;               
% Average coolant temperature
Tji = 303.15;
Tj =(Tji+Tjo)/2;     

% Overall heat transfer coeff   
 alpha = 0.4;  
 U = U0-alpha*X;        

 delHp = 57800;                        

% ---------------------------------------
%           Rates of reaction
% ======================================= 

% Fujita-Doolittle equation
Tgp = 114 +273.25   ;                      
A = 0.168-8.21e-6*(T-Tgp)^2;
B = 0.03;
g = exp(2.303*Fvm/(A + B*Fvm));          

% Dissociation rate
F = 0.58; 
Kd = (6.32e16*exp(-15.43e3/T));            

% Propagation rate  
Tep = 5.4814e-16*exp(13982/T);               
Kp0 = 2.952e7*exp(-4353/(1.987*T));     
Kp = (Kp0*g)./(g + (Tep*P0.*Kp0));         

% Termination rate  
Tet = (1.1353e-22*exp(17420/T))./I0;      
Kt0 = 5.88e9*exp(-701/(1.987*T));        
Kt = (Kt0*g)./(g + (Tet*P0.*Kt0));        
Ktc = 0;
Ktd = Kt ;                                


% -------------------------------------------- %
%       ODE's
% -------------------------------------------- % 
 dIdt = -Kd*I - ((Fev*I.*P0.*(1 - X)*Kp)./(1 + Fev*X)); 
 dXdt = Kp*(1 - X).*P0;     
 dP0dt = (-Fev*P0.*P0.*(1 - X)./(1 + Fev*X)).*Kp + 2*F*Kd*I - Kt*P0.*P0; 
 dP1dt = (-Fev*P0.*P1.*(1 - X)./(1 + Fev*X)).*Kp + 2*F*Kd*I - Kt*P0.*P1 + (Kp*M0*(1 -   X)./(1 + Fev*X)).*P0;
dP2dt = (-Fev*P0.*P2.*(1 - X)./(1 + Fev*X)).*Kp + 2*F*Kd*I - Kt*P0.*P2 + (Kp*M0*(1 - X)./(1 + Fev*X)).*(2*P1 + P0);
dQ0dt = (-Fev*P0.*Q0.*(1 - X)./(1 + Fev*X)).*Kp + Ktd*P0.*P0 + 0.5*Ktc*P0.*P0;
dQ1dt = (-Fev*P0.*Q1.*(1 - X)./(1 + Fev*X)).*Kp + Ktd*P0.*P1 + Ktc*P0.*P1;
dQ2dt = (-Fev*P0.*Q2.*(1 - X)./(1 + Fev*X)).*Kp + Ktd*P0.*P2 + Ktc*(P1.*P0 + P1.^2);
dMdt = (-Kp*P0*M0*(1 - X)./(1 + Fev*X)).*((Fev*(1 - X)./(1 + Fev*X)) + 1);
  Rm = (-delHp)*dMdt;                  
dTjodt = (Mc*Cpc*(Tji-Tjo)+ U*At*(T-Tj))/(Vc*Rhoc*Cpc/18);
dTdt = (Qh+(Rm*V*MMWm)-(U*At*(T-Tj)))/(V*Rho*Cp);

DXDT =[dIdt;dXdt;dP0dt;dP1dt;dP2dt;dQ0dt;dQ1dt;dQ2dt;dMdt;dTjodt;dTdt];