num=[1,-1]; den=[1,2,1]; G=tf(num,den);
nW=0.62*[1,1.2,1]; dW=conv([1,0.001],conv([1,1.2],[0.001,1]));
[a,b,c,d]=tf2ss(num,den); S=mksys(a,b,c,d);
W1=[0,nW; dW]; TSS_2=augtf(S,W1,[1e-5;1],[]);
Fh2=h2lqg(TSS_2); [af,bf,cf,df]=branch(Fh2); 
F3=zpk(ss(af,bf,cf,df))

G_o3=G*F3; G_c3=feedback(G_o3,1);
step(G_c3), 
figure, ngrid('new'), nichols(G3_o), axis([-360,0,-40,40])

w=logspace(-5,5); 
g1=feedback(1,G*F1); [m1,p1]=bode(g1,w);
g2=feedback(1,G*F2); [m2,p2]=bode(g2,w);
g3=feedback(1,G*F3); [m3,p3]=bode(g3,w); 
[m,p]=bode(tf(nW,dW),w); 
m=20*log10(m(:)'); m1=20*log10(m1(:)'); 
m2=20*log10(m2(:)'); m3=20*log10(m3(:)'); 
semilogx(w,m,'-',w,m1,'--',w,m2,':',w,m3,'-.'), 
figure; semilogx(w,m+m1,'--',w,m+m2,':',w,m+m3,'-.')