A=[-3.6994,0.6627,-2.3879;0.6627,-1.4220,0.4994;-2.3879,0.4994,-3.2736]; 
B=[0; 0; -0.0449]; C=[ -0.7989,-0.7652,0.8617]; D=0;
H1=[-29.9482; 7.2402; -27.2489];  eig(A-H1*C)

[xh,x,t]=simobsv(ss(A,B,C,D),H1); plot(t,x,'-',t,xh,':')

H2=[-650.74; 2173.52; 1355.35]; eig(A-H2*C)

[xh,x,t]=simobsv(ss(A,B,C,D),H2); plot(t,x,'-',t,xh,':')

A1=A; A1(1,1)=0.95*A(1,1); 
[y,t,x]=step(ss(A1,B,C,D));
[y1,t,xh1]=step(ss((A-H1*C),(B-H1*D),C,D),t);
[y2,t,xh2]=lsim(ss((A-H1*C),H1,C,D),y,t);
xh=xh1+xh2; plot(t,x,'-',t,xh,':')

[y1,t,xh1]=step(ss(A-H2*C,B-H2*D,C,D),t);
[y2,t,xh2]=lsim(ss(A-H2*C,H2,C,D),y,t);
xh=xh1+xh2; plot(t,x,'-',t,xh,':')