clear all;
close all; 
ts=0.001;
sys=tf(50,[0.125,7, 0]);
dsys=c2d(sys,ts,'z');
[num,den]=tfdata(dsys,'v'); 
u_1=0.0;u_2=0.0;
y_1=0.0;y_2=0.0;
x=[0,0,0]';
error_1=0;
error_2=0;
for k=1:1:1000
time(k)=k*ts;   
S=2;
if S==1
    kp=10;ki=0.1;kd=15;          
    rin(k)=1;                       %Step Signal
elseif S==2
    kp=10;ki=0.1;kd=15;          %Sine Signal
    rin(k)=0.5*sin(2*pi*k*ts);           
end 
du(k)=kp*x(1)+kd*x(2)+ki*x(3);    %PID Controller
u(k)=u_1+du(k);
%Restricting the output of controller
if u(k)>=5       
   u(k)=5;
end
if u(k)<=-5
   u(k)=-5;
end
%Linear model
yout(k)=-den(2)*y_1-den(3)*y_2+num(2)*u_1+num(3)*u_2; 
error(k)=rin(k)-yout(k);
 %Return of parameters
u_2=u_1;u_1=u(k);
y_2=y_1;y_1=yout(k);   
x(1)=error(k)-error_1;          %Calculating P
x(2)=error(k)-2*error_1+error_2;   %Calculating D
x(3)=error(k);      %Calculating I 
error_2=error_1;
error_1=error(k);
end
figure(1);
plot(time,rin,'b',time,yout,'r');
xlabel('time(s)'),ylabel('rin,yout'); 
figure(2);
plot(time,error,'r')
xlabel('time(s)');ylabel('error');