Here is the frequency response function, whereW0__ is the wheel hop resonant frequency, Wt is the tyre ‘jumping’ resonant frequency. X is the normalized damping coefficient, and Zr is the Fourier spectrum corresponding to the irregularity profile. The Fourier transform of the the vertical force applied from the vehicle to the ground, Ft is easily obtained from via replacing Zw and Zr by their Fourier spectra and using Eq.
Note that for tracked vehicles the values of tyre compliance Kt, characterizing the elasticity of solid rubber coating of road wheels, are quit high in comparison witg the stiffness od suspension Ks. In this case the wheel follows the track irregularities Zr and the dynamic force applied to the ground through the track are defined mainly by the stiffness of suspension Ks. Indeed, as follows from Eq. สูตรที่6, if to assume that Kt >> Ks, the transfer function Zw becomes