clear all; clc
k1 = 1; k2 = 4; b1 = 0.2; b2 = 0.1; m1 = 1; m2 = 2;
A = [0 0 1 0;
    0 0 0 1;
    -k1/m1 k1/m1 -b1/m1 b1/m1;
    k1/m2 -(k1+k2)/m2 b1/m2 -(b1+b2)/m2];
B = [0 0;
    0 0;
    1/m1 0;
    0 1/m2];
C = [1 0 0 0;
    0 1 0 0];
D = zeros(2,2);
%Form state-space representation
Gss = ss(A,B,C,D)
%Plot singular values
sigma(Gss)
%H-norm
hinfnorm(Gss)