t1=1; t2=2; t3=3; 
z = 1;
sys1 = tf(z, [t1 1]);
sys2 = tf(z, [t2 1]);
sys3 = tf(z, [t3 1]);
[y1,tt1]=step(sys1,15);
[y2,tt2]=step(sys2,15);
[y3,tt3]=step(sys3,15);
plot(tt1,y1,'k-', tt2,y2,'k--', tt3,y3,'k-.')
xlabel('t');
ylabel('y / Z_1');
legend('T_1=1','T_1=2','T_1=3',4)

set(1, 'PaperUnits', 'centimeters')
set(1, 'PaperPosition', [3 10 11 9])
print -deps 'obr413.eps'

plot(tt1,y1,'k-',[0 15],[z z],'k:')
axis([0 8 0 1.3])
hold on
plot([1 1],[0,1.05],'k:',[2 2],[0,1.05],'k:',[3 3],[0,1.05],'k:')
y11 = z * (1 - exp(-1/t1));
y21 = z * (1 - exp(-2/t1));
plot([0 1],[0,1],'k--',[1 2],[y11,1],'k--',[2 3],[y21,1],'k--')
hold off
xlabel('t');
ylabel('y / Z_1');
text(0.5,1.05, 'T_1');
text(1.5,1.05, 'T_1');
text(2.5,1.05, 'T_1');
set(1, 'PaperUnits', 'centimeters')
set(1, 'PaperPosition', [3 10 11 9])
print -deps 'obr412.eps'
