figure(4) 
clf;
clear;

robot = tf(1, [1 8 25]);		

Kp = 0.5;			% defines the proportional controller gain
Kd = 0.5;

t=0:0.01:2;

perturbation = 0;

pdcontroller=tf([Kd Kp], 1);
pdcontrol=feedback(pdcontroller*robot+perturbation, 1);

figure(4)
step(pdcontrol, t)
title('PD control')
