num=-[948.12, 30325, 56482, 1215.3];
den=[1, 64.554, 1167, 3728.6, -5495.4, 1102, 708.1];
G=ss(tf(num,den));

Q=G.c'*G.c; R=1; [Kc,P]=lqr(G.a,G.b,Q,R); 
nyquist(ss(G.a,G.b,Kc,0))

Xi=1e-4; Theta=1e-5; 
G1=ss(G.a,[G.b, G.b],G.c,[G.d,G.d]);
[K_Sys,L,P2]=kalman(G1,Xi,Theta);
a1=G.a-G.b*Kc-L*G.c; 
G_o=G*ss(a1,L,Kc,0);
nyquist(G_o)
[Gm,Pm,Wcg,Wcp]=margin(G_o); [Gm,Pm,Wcg,Wcp]