DEFINITIONS OF REFERENCE FRAMES USED IN VEHICLE DYNAMICS
The principal reference frames used in vehicle dynamics are defined below, and illustrated in Figs. 4.2 to 4.7.
4.2.1 INERTIAL REFERENCE FRAME Fz (INERTIAL AXES, 07x7yzz7)
In every dynamics problem there must be an inertial reference frame, either explicitly defined, or lurking implicitly in the background. This frame is fixed, or in uniform rectilinear translation, relative to the distant stars; in it Newton’s second law is valid for the motion of a particle, in the sense that if f be the sum of all external forces acting on the particle, and a its acceleration relative to Fz, then f = та. If a is acceleration relative to a reference frame that has rotation, or acceleration of its origin, this equation does not hold, and additional terms that depend on the motion of the reference
frame must be added to the equation (see Sec. 5.1). The velocity of the vehicle mass center relative to FT is denoted Vz.