PID

[fleeking]

%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('sy3_1',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');

被控对象函数文件：sy3_1.m
function dy = sy3_1(t,y,flag,para)
u=para;
J=0.0067;B=0.1;
dy=zeros(2,1);
dy(1) = y(2);
dy(2) = -(B/J)*y(2) + (1/J)*u;

有人能帮我解释一下么？？