wn=4;
zeta=0.3;
Ao=wn^2;
Bo=[1 2*zeta*wn 0];
Ac=wn^2;
Bc=[1 2*zeta*wn wn^2];
Go=tf(Ao,Bo);
Gc=tf(Ac,Bc);
figure(1)
step(Go)
grid;
figure(2)
step(Gc)
grid;