%  Tutorial 2. Part 2.  %    Disk drive problem%    Robust stability evaluation using the structured
%    singular value.
clear
%  Define the state model for the transfer function M
A=[  -1000   0   -50
      5000   0    0 
   -   0     1  -20];
B=[-1 0 
    0 0 
    0 -1 ];
C=[500 0  0
     0 0  10];
D=zeros(2,2);
%  Generate the frequency response for this system.
w=logspace(-4,3);
M=pck(A,B,C,D);
fr=frsp(M,w);
%  Compute the structured singular value from the frequency response.
%    Compute the structured singular value mu.
muM=mu(fr);%  Plot the results.
vplot('liv,lm',muM)
xlabel('Frequency (rad/sec)')
ylabel('Magnitude')
%  Compute the maximum of mu over the frequency range studied.
maxmu=max(muM(:,1))