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%Big Delay PID Control with Smith Algorithm 
clear all;close all; 
Ts=20; 
 
%Delay plant 
kp=1; 
Tp=60; 
tol=80; 
sys=tf([kp],[Tp,1],'inputdelay',tol); 
dsys=c2d(sys,Ts,'zoh'); 
[num,den]=tfdata(dsys,'v'); 
 
M=1; 
%Prediction model 
if M==1  %No Precise Model: PI+Smith 
   kp1=kp*1.10; 
   Tp1=Tp*1.10; 
   tol1=tol*1.0; 
elseif M==2|M==3  %Precise Model: PI+Smith 
   kp1=kp; 
   Tp1=Tp; 
   tol1=tol; 
end 
 
sys1=tf([kp1],[Tp1,1],'inputdelay',tol1); 
dsys1=c2d(sys1,Ts,'zoh'); 
[num1,den1]=tfdata(dsys1,'v'); 
 
u_1=0.0;u_2=0.0;u_3=0.0;u_4=0.0;u_5=0.0; 
e1_1=0; 
e2=0.0; 
e2_1=0.0; 
ei=0; 
 
xm_1=0.0; 
ym_1=0.0; 
y_1=0.0; 
 
for k=1:1:600 
    time(k)=k*Ts; 
    
S=2; 
if S==1 
   rin(k)=1.0;     %Tracing Step Signal 
end 
if S==2 
   rin(k)=sign(sin(0.0002*2*pi*k*Ts));  %Tracing Square Wave Signal 
end 
 
%Prediction model 
xm(k)=-den1(2)*xm_1+num1(2)*u_1; 
ym(k)=-den1(2)*ym_1+num1(2)*u_5;  %With Delay  
 
yout(k)=-den(2)*y_1+num(2)*u_5; 
 
if M==1       %No Precise Model: PI+Smith 
   e1(k)=rin(k)-yout(k); 
   e2(k)=e1(k)-xm(k)+ym(k); 
	ei=ei+Ts*e2(k); 
	u(k)=0.50*e2(k)+0.010*ei; 
   e1_1=e1(k); 
elseif M==2   %Precise Model: PI+Smith 
   e2(k)=rin(k)-xm(k); 
	ei=ei+Ts*e2(k); 
	u(k)=0.50*e2(k)+0.010*ei;     
	e2_1=e2(k); 
elseif M==3  %Only PI 
   e1(k)=rin(k)-yout(k); 
	ei=ei+Ts*e1(k); 
	u(k)=0.50*e1(k)+0.010*ei;    
   e1_1=e1(k); 
end 
 
%----------Return of smith parameters------------ 
xm_1=xm(k); 
ym_1=ym(k); 
 
u_5=u_4;u_4=u_3;u_3=u_2;u_2=u_1;u_1=u(k); 
y_1=yout(k); 
end 
plot(time,rin,'b',time,yout,'r'); 
xlabel('time(s)');ylabel('rin,yout');