ex6_4.m

离散控制系统设计的MATLAB 代码

%%%%%%%%%%%%%%%%%% Example 6.4 %%%%%%%%%%%%%%%%%%
%   Discrete-Time Control Problems using        %
%       MATLAB and the Control System Toolbox   %
%   by J.H. Chow, D.K. Frederick, & N.W. Chbat  %
%         Brooks/Cole Publishing Company        %
%                September 2002                 %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%   ---- Bandpass filtering ----
%
clear
disp('Example 6.4')

Ts = 0.01;                      % sampling period
w0 = 50*pi;                     % center frequency
a = 0.5, b = 0.95, K = 0.13
%-- build bandpass filter, where j is sqrt(-1)
num = K*conv([1 -a*exp(j*w0*Ts)],[1 -a*exp(-j*w0*Ts)]);
den = conv([1 -b*exp(j*w0*Ts)],[1 -b*exp(-j*w0*Ts)]);
G = tf(num,den,Ts)			    % bandpass filter as TF object

figure
ucircle,axis equal,hold on
pzmap(G),hold off               % plot poles and zeros
title(' ')
%--- plot frequency response magnitude and phase ---
w = logspace(-2,0,200)*pi/Ts;   % specify frequency range
figure
bode(G,w)                       % frequency response plot
%--- plot output of the filter ---
t = [0:Ts:10.0-Ts];             % time array from 0 to 9.99 s
e = cos(14*pi*t)+cos(50*pi*t)+cos(86*pi*t);  % DT signal
y = lsim(G,e);                  % filter output
t95 = [951:1000]';

figure
stem(t(t95),y(t95),':o'), grid
title('Output signal of bandpass filter of Example 6.4 shown for 9.5 < t < 10.0')
xlabel('Time (s)')
ylabel('Amplitude')
%%%%%%%%%%