@brief Get the AMotor axes.
@param anum selects the axis to change (0,1 or 2).
@param rel Each axis can have one of three `relative orientation'' modes.
\li 0: The axis is anchored to the global frame.
\li 1: The axis is anchored to the first body.
\li 2: The axis is anchored to the second body.
@ingroup joints
@brief Get the AMotor axes. @param anum selects the axis to change (0,1 or 2). @param rel Each axis can have one of three `relative orientation'' modes. \li 0: The axis is anchored to the global frame. \li 1: The axis is anchored to the first body. \li 2: The axis is anchored to the second body. @ingroup joints