exp4_10_.m

Matlab复杂分析模拟讲义及例程

%exp4_10_.m
%求典型二阶系统自然振荡频率固定，阻尼比变化时的波特图
clear
clc
close all
wn=6;
kosi=[0.1:0.1:1.0];
num=wn^2;
for kos=kosi
   den=[1 2*kos*wn wn^2];
   [mag,pha,w1]=bode(num,den);
   magg=20*log10(mag);
   subplot(211)
   hold on
   semilogx(w1,magg);
   % 注意在所绘制的图形窗口会发现x轴并没有取对数分度
   subplot(212);hold on
   semilogx(w1,pha);
end
subplot(211)
grid on
title('bode plot')
xlabel('frequency(rad/sec)')
ylabel('gain db')
text(6.4,16,'kosi=0.1')
text(1,-18,'kosi=1.0')
subplot(212)
grid on
xlabel('frequency(rad/sec)')
ylabel('phase deg')
text(5,-20,'kosi=0.1')
text(8,-185,'kosi=1.0')
hold off