The mathematical model of the rigid body presents the Cartesian coordinate frame S ≡ OXYZ associated with the body (Fig. 3.1). The origin O and the X-, Y-, and Z-axis are usually associated with the mechanical and manufacturing bases of the link, such as guideways surfaces, axes, accurate planes and cylindrical surfaces, local supports, etc. The point K of the rigid body (Fig. 3.1a) is defined through the Cartesian coordinated x_K, y_K, and z_K presenting elements of a position vector: