PID matlab

clear all; 
close all;

ts=0.001;
sys=tf(400,[1,50,0]);
dsys=c2d(sys,ts,'z');
[num,den]=tfdata(dsys,'v');

u_1=0.0;u_2=0.0;u_3=0.0;
y_1=0;y_2=0;y_3=0;

x=[0,0,0]';

error_1=0;
error_2=0;
for k=1:1:1000
    time(k)=k*ts;
    
    rin(k)=1.0;
    kp=8;
    ki=0.10;
    kd=10;
    
    du(k)=kp*x(1)+kd*(2)+ki*x(3);
    u(k)=u_1+du(k);
    if u(k)>=10;
        u(k)=10;
    end
    if u(k)<=-10;
        u(k)=-10;