fig724.m

realize analysis and design for computer-controlled system

% Generates Fig 7.24
% Computer Controlled Systems (3rd ed)
% Author: B. Wittenmark
% Last edit: 1997-07-09
% Copyright (c) 1996 by K. J. 舠tr鰉, B. Wittenmark and
% Department of Automatic Control, Lund Institute of
% Technology, Lund, Sweden

clear;
newplot;
set(gcf,'PaperUnits','centimeters','PaperPosition',[2 2 13 9.5])
set(gcf,'Units','centimeters','position',get(gcf,'PaperPosition'))

lw=0.9;
N=500;
h=1;

clf
w=linspace(0.01,20,N);

fr1=zeros(N,3);
for j=1:N 
   fr1(j,1)=w(1,j); 
   fr1(j,2)= (1-exp(-i*w(1,j)*h))/(i*w(1,j)*h);
   fr1(j,3)=fr1(j,2)*(1+i*w(1,j)*h)/(fr1(j,2)+i*w(1,j)*h);
end;

subplot(2,1,1);
abs1=abs(fr1(:,2));
abs2=abs(fr1(:,3));
plot(fr1(:,1),abs1,'k--',fr1(:,1),abs2,'m','Linew',lw)
axis([0. 20 0 1.6])
set(gca,'Fontsize',9,'Fontname','NewCenturySchlbk');
set(gca,'ytick',[0 1]);
set(gca,'xtick',[0 10 20]);
ylabel('Gain','Fontname','NewCenturySchlbk','Fontsize',9)

subplot(2,1,2);
arg1=180/pi*unwrap(angle(fr1(:,2)));
arg2=180/pi*unwrap(angle(fr1(:,3)));
plot(fr1(:,1),arg1,'k--',fr1(:,1),arg2,'m','Linew',lw)
axis([0,20,-200,0]);
set(gca,'Fontsize',9,'Fontname','NewCenturySchlbk');
set(gca,'xtick',[0 10 20]);
set(gca,'ytick',[-200 -100 0]);
xlabel('Frequency, rad/s','Fontname','NewCenturySchlbk','Fontsize',9)
ylabel('Phase','Fontname','NewCenturySchlbk','Fontsize',9)

drawnow
ylblalgn;