fig725.m

realize analysis and design for computer-controlled system

% Generates Fig 7.25
% 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=1000;
a=[1 1 0];
b=[1];
h=0.05;
wn=pi/h;

clf
w=logspace(-1,3,N);

fr1=zeros(N,3);
for j=1:N 
   fr1(j,1)=w(1,j); 
%   fr1(j,2)= i*(1-exp(-i*w(1,j)*h))/h/(1+i*w(1,j));
fr1(j,2)= (1-exp(-i*w(1,j)*h))/(i*w(1,j)*h)/(1+i*w(1,j));
fr1(j,3)=1/(1+i*w(1,j));
end;
%fr2=frc(1,[1 1],0,-1,3,N);

%scale=[1e-1,1e3,1e-5,5,-300,0];
%bopl([fr1,fr2(:,2)],scale)
subplot(2,1,1);
abs1=abs(fr1(:,2));
abs2=abs(fr1(:,3));
loglog(fr1(:,1),abs1,'m',fr1(:,1),abs2,'k--','Linew',lw)
axis([0.1 1000 1e-5 2])
set(gca,'Fontsize',9,'Fontname','NewCenturySchlbk');
set(gca,'ytick',[0.001 1e0]);
set(gca,'xtick',[0.1 10 1000]);
ylabel('Gain','Fontname','NewCenturySchlbk','Fontsize',9)
hold on
plot([5 5],[1e-5 2],'k:','Linew',lw)
plot([60 60],[1e-5 2],'k:','Linew',lw)
plot([130 130],[1e-5 2],'k:','Linew',lw)
plot([wn wn],[1e-5 2],'k--','Linew',lw)

subplot(2,1,2);
arg1=180/pi*unwrap(angle(fr1(:,2)));
arg2=180/pi*unwrap(angle(fr1(:,3)));
semilogx(fr1(:,1),arg1,'m',fr1(:,1),arg2,'k--','Linew',lw)
axis([0.1 1000 -300 0]);
set(gca,'Fontsize',9,'Fontname','NewCenturySchlbk');
set(gca,'xtick',[0.1 10 1000]);
set(gca,'ytick',[-300 -200 -100 0]);
xlabel('Frequency, rad/s','Fontname','NewCenturySchlbk','Fontsize',9)
ylabel('Phase','Fontname','NewCenturySchlbk','Fontsize',9)
hold on
plot([5 5],[0 -300],'k:','Linew',lw)
plot([60 60],[0 -300],'k:','Linew',lw)
plot([130 130],[0 -300],'k:','Linew',lw)
plot([wn wn],[0 -300],'k--','Linew',lw)

drawnow
ylblalgn;