Tddq1 = diff(T,dx);
dTddq2 = diff(T,dy);
dTddq3 = diff(T,dPSI);
dTddq  = [ dTddq1 ; dTddq2 ; dTddq3 ];
dTddq  = subs(dTddq,symVariables,symfunVariables);
ddTddq = diff(dTddq,t);

%% State equations
% <html>
% <p>The equations of motion are</p>
% <p>
%     \begin{eqnarray}
%     \nonumber m_{\rm T} \ddot{x} &=& F_{x,{\rm F}} \cos \left( \psi + \delta_{\rm F} \right) - F_{y,{\rm F}} \sin \left( \psi + \delta_{\rm F} \right) + F_{x,{\rm R}} \cos \left( \psi + \delta_{\rm R} \right) - F_{y,{\rm R}} \sin \left( 