% program ch13ex11.m
% program to compute the dynamic error in estimation for shell column
% Babu Joseph Washington University, St.Louis Mar 13 1993
%
% define component matrices
for k=1:20, % for 20 different time constants
   tau=k*5; % varying from 5 to 100
   t(k)=tau;
   % define all transfer functions
sys1=tf([1.27],[45 1]);
sys2=tf([-28.1  -3.3],[11*tau 11+tau 1]);
sys3=tf([25.12 2.09],[5*tau 5+tau 1]);
sys4=tf([1.44],[40 1]);
sys5=tf([-30.76 -3.6195],[6*tau 6+tau 1]);
sys6=tf([26 2.166],[19*tau 19+tau 1]);
q=parallel(sys1,sys2);q1=parallel(q,sys3);
q=parallel(sys4,sys5);q2=parallel(q,sys6);
w=logspace(-3,1,30);
[q1mag,phase]=bode(q1,w);
[q2mag,phase]=bode(q2,w);
for i=1:30
   q=[q1mag(i) q2mag(i)]';s=svd(q);smax(i)=max(s);
end;
normq(k)=max(smax);
end
plot(t,normq);