%Discrete PID control for continuous plant
clear all;
close all;

ts=0.001;  %Sampling time
xk=zeros(2,1);
e_1=0;
u_1=0;

for k=1:1:2000
time(k) = k*ts;

rin(k)=0.50*sin(1*2*pi*k*ts);
  
para=u_1;
tSpan=[0 ts];
[tt,xx]=ode45('chap1_2f',tSpan,xk,[],para);
xk = xx(length(xx),:);
yout(k)=xk(1); 

e(k)=rin(k)-yout(k);
de(k)=(e(k)-e_1)/ts; 

u(k)=20.0*e(k)+0.50*de(k);
%Control limit
if u(k)>10.0
   u(k)=10.0;
end
if u(k)<-10.0
   u(k)=-10.0;
end

u_1=u(k);
e_1=e(k);
end
figure(1);
plot(time,rin,'r',time,yout,'b');
xlabel('time(s)'),ylabel('rin,yout');
figure(2);
plot(time,rin-yout,'r');
xlabel('time(s)'),ylabel('error');