How to rectify this error message while working on hinfmix command < ??? Error using ==> lti.subsref at 56>

Dear All,

Needed help to solve several errors while working on a hinfmix problem.

Appreciate your kind advise.

 ??? Error using ==> lti.subsref at 56
Use two or more subscripts to index into MIMO
models or LTI arrays, as in the "sys(2,1)"
command.

Error in ==> islsys at 11 sys=sys(:);

Error in ==> hinfmix at 59 elseif ~islsys(G),

Error in ==> MixedH2nHinf_singleloop at 63 [gopt,h2opt,k]=hinfmix(P_ss,length,obj);

------------------------------------------------------------------

The m file code as below:

%Mixed H2 and H infinity Synthesis

%Single loop calculation

%-----------------------------------------------------------------------%

%Fixed Parameter

Is=16.9 ; %Inertia Tw=2 ; %system respond time %-----------------------------------------------------------------------%

%Variable

%gam=H infinity constraint gam=0.001;

%V= H 2 constraint v=0.001;

%W1= weighting function to state the weighting on H infinity control

W1=1e-5;

%W2= weighting function to state the weighting on H2 control

W2=1e-6;

%-----------------------------------------------------------------------% %Defined Plant Matrix(different from Hinf)% %-----------------------------------------------------------------------%

sat_tf=tf(1,[Is 0 0]); mix_tf=tf(1,[Is*Tw Is 0 0]);

%Plant Transfer Function

P_Zinf_W=[0 0]; P_Zinf_u=[W1]; P_Z2_W=[-W2*sat_tf W2]; P_Z2_u=[W2*mix_tf]; P_V_W=[sat_tf 0;-sat_tf 1]; P_V_u=[-mix_tf;mix_tf];

p_tf=[P_Zinf_W P_Zinf_u;P_Z2_W P_Z2_u;P_V_W P_V_u];

P_ss=ss(p_tf,'min'); %-----------------------------------------------------------------------% %Apply into mixed h2 and hinfinity synthesis

%Length=[Z2, y, u]

length= [2 2 2];

%obj= define constraints and trade off %obj= [gam,v,W1,W2]

obj= [gam v W1 W2];

[gopt,h2opt,k]=hinfmix(P_ss,length,obj); %-----------------------------------------------------------------------%