In order to calculate accelerations and velocities in directions of interest (such as fore and aft for
performance or left and right for turning behavior), it is necessary to define axis systems to which the
accelerations and velocities and the forces/torques causing them can be referred. Since we live in a
three-dimensional world, three reference axes at right angles (90°) to each other which meet at a
common point (the axis system "origin") are the basic and sufficient requirements for these axis systems.
x-y-z are the vehicle coordinate in longitudinal, lateral and vertical respectively accompany with roll pitch
and yaw which are the rotation about x, y and z as shown in figure 1