fig33.m

realize analysis and design for computer-controlled system

% Generates Fig 3.3
% Computer Controlled Systems (3rd ed)
% Author: B. Wittenmark
% Last edit: 1997-06-27
% Copyright (c) 1996 by K. J. 舠tr鰉, B. Wittenmark and
% Department of Automatic Control, Lund Institute of
% Technology, Lund, Sweden

newplot;clf;
set(gcf,'PaperUnits','centimeters','PaperPosition',[2 2 13 8])
set(gcf,'Units','centimeters','position',get(gcf,'PaperPosition'))

lw=0.9;

m=200;
n=5;
h=0.4;
w=logspace(-4,pi,m)/h;
i=sqrt(-1);
z=exp(i*w*h);
ac=[-1.4 -1;1 0];bc=[1;0];cc=[0 1];dc=0;
[ph,ga]=c2d(ac,bc,h);
[b,a]=ss2tf(ph,ga,cc,dc,1);
gz=polyval(b,z)./polyval(a,z);
ny1=gz.';
w=logspace(-4,2,m);
ny2 = freqresp(ac,bc,cc,dc,1,i*w);
plot(ny1,'k-','Linew',lw)
hold on;
plot(ny2,'k--','Linew',lw)
axis('equal')
axis([-0.6 1.1 -1 0.2])
%title('Fig 3.6')
set(gca,'Fontsize',9,'Fontname','NewCenturySchlbk');
ylabel('Imaginary axis','Fontname','NewCenturySchlbk','Fontsize',9)
xlabel('Real axis','Fontname','NewCenturySchlbk','Fontsize',9)
set(gca,'xtick',[-0.5 0 0.5 1],'ytick',[-1 -0.5 0]);
plot([0 0],[-1.6 1.6],'k:',[-1 2],[0 0],'k:')
arrow2([-0.2615 -0.526],118*pi/180)
arrow2([-0.1755 -0.496],115*pi/180)