Loopshaping loopsyn > Robust control toolbox

Hello,

I'm trying to find controller my 1x2 (1 input, 2 output) model using loopsyn command; I'm getting error below when I tried to use command loopsyn

??? Error using ==> lti.loopsyn at 204 Ill-posed problem -- plant G cannot have more outputs than inputs

Error in ==> Untitled4 at 15 [K,CL,GAM,INFO]=loopsyn(ltcp_nom,Gd); % Design a loop-shaping controller K

See my m code below that I'm using for system model, and please give me advise that where am I doing mistake ??

Thanks, Özgür

clc;

clear;

g=9.81;

b=0.1;

M_n=3;

m_n=1;

l_n=1;

A_n=[0 1 0 0;0 -b/M_n -m_n*g/M_n 0;0 0 0 1;0 b/M_n*l_n (M_n+m_n)*g/M_n*l_n 0];

B_n=[0;1/M_n;0;-1/M_n*l_n];

C_n=[1 0 0 0;0 0 1 0];

D_n=[0;0];

ltcp_nom = ss(A_n,B_n,C_n,D_n);

s=tf('s'); w0=0.4; Gd=w0/s;

[K,CL,GAM,INFO]=loopsyn(ltcp_nom,Gd); % Design a loop-shaping controller K