funVariables,symVariables);               % P_{F/O}
PRO   = subs(PRO_t,symfunVariables,symVariables);               % P_{R/O}

%% Velocity 
%
% <html>
% <p>The angular velocity is</p>
% <p>
%     \begin{equation}
%     {\bf w}_{\rm T} = \dot{\psi} {\bf k}. \label{eq:tractorvelangular}
%     \end{equation}
% </p>
% <p>CG velocity</p>
% <p>
%     \begin{equation}
%     {\bf v}_{\rm T} = \dot{x} {\bf i} + \dot{y} {\bf j} \label{eq:tractorveltranslation} 
%     \end{equation}
% </p>
% <p>Velocities of each axle