function phi = fcn(psi,u,v,w,r,u_v_dot,v_v_dot,w_v_dot,r_v_dot)
% P-CABS Regressor 
phi = [u_v_dot -v*r 0 0 abs(u)*u 0 0 0 0 0 0 -cos(psi) sin(psi) 0;
       u*r v_v_dot 0 0 0 abs(v)*v 0 0 0 0 0 -sin(psi) -cos(psi) 0;
       0 0 w_v_dot 0 0 0 abs(w)*w 0 0 0 1 0 0 0;
       -u*v u*v 0 r_v_dot 0 0 0 abs(r)*r 0 0 0 0 0 0]; 
   
 %ABSwB regressor             
% phi = [u_v_dot -v*r 0 0 abs(u)*u 0 0 0 0 0 0 0 0 0;
%        u*r v_v_dot 0 0 0 abs(v)*v 0 0 0 0 0 0 0 0;
%        0 0 w_v_dot 0 0 0 abs(w)*w 0 0 0 1 0 0 0;
%        -u*v u*v 0 r_v_dot 0 0 0 abs(r)*r 0 0 0 0 0 0];

%  Antonelli regressor  
% phi = [0 0 0 0 0 0 0 0 0 0 0 -cos(psi) sin(psi) 0;
%        0 0 0 0 0 0 0 0 0 0 0 -sin(psi) -cos(psi) 0;
%        0 0 0 0 0 0 0 0 0 0 1 0 0 0;
%        0 0 0 0 0 0 0 0 0 0 0 0 0 0];