www.pudn.com > chap1.rar > chap1_6.m

%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;              % D/A 
tSpan=[0 ts]; 
[tt,xx]=ode45('chap1_6f',tSpan,xk,[],para); 
xk = xx(length(xx),:);    % A/D 
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');