www.pudn.com > controlsystem.ZIP > EX3022.M

% Example 3.22 
% 
num=[1 1]; 
den=conv([1 2],conv([1 2],[1 2])); 
w=logspace(-1,2); 
t=0.5; 
[m1,p1]=bode(num,den,w); 
p1=p1-t*w'*180/pi; 
[n2,d2]=pade(t,4); 
numt=conv(n2,num); dent=conv(den,d2); 
[m2,p2]=bode(numt,dent,w); 
subplot(2,1,1); 
semilogx(w,20*log10(m1),w,20*log10(m2),'y--'); 
subplot(2,1,2); 
semilogx(w,p1,w,p2,'y--'); 
subplot(2,1,1);grid on 
title('Bode Plot'); 
xlabel('Frequency (rad/sec)'); 
ylabel('Gain dB'); 
subplot(2,1,2);grid on 
xlabel('Frequency (rad/sec)'); 
ylabel('Phase deg');