Problem: double mass-spring-damper bode plot. Is it correct ?

Hello guys :),

i am not sure whether my results of the bode plot is correct. I am reading a dissertation right now, where the author is analysing following double mass-spring-damper system. The matrices for the state-space model are at the end of the post.

His results are following bode plots

When i am plotting the transfer function of Gza-zr(s) for example, i am getting completly other eigenfrequencies (~9Hz and ~70Hz) and i am not sure, what i've done wrong

mr=36.6;
ma=267;
ca=18700;
cr=184000;
da=1398;
dr=0;

A=[0 1 0 -1; -ca/ma -da/ma 0 da/ma; 0 0 0 1; ca/mr da/mr -cr/mr -da/mr+dr/mr];
bu=[0; 1/ma; 0; -1/mr];
bw=[0; 0; -1; dr/mr];
du=[0; 0; 1/ma];
dw=[0; dr; 0];
C=[1 0 0 0; 0 0 -cr -dr;-ca/ma -da/ma 0 da/ma];


 sys=ss(A,B,C,D);
%bode(sys)
 s=tf('s');
 G=C*inv(s*eye(4)-A)*bw+dw;
 G1=G(1,1); %G_za-zr(s)
 G2=G(2,1); %G_Fz,dyn(s)
 G3=G(3,1); %G_ppza(s)

[Jörg Schuler]

B and D are not defined in your example.