2D spectrums of tire acceleration, respectively. Figure 11 shows the 2D spectrum of tire
dynamic load. The nonstationary response spectrum analysis of the vehicle system shows
that the low-spatial frequency ingredient has a main role with vehicle speed increasing when
the vehicle moves in a constant acceleration. With the speed increasing, the peak values
of power spectrum of seat and body acceleration, as well as the low frequency values of
power spectrum of dynamic tire loads, are not monotonously increasing, and some local
values are decreasing. The changing of relative displacement of vehicle suspensions is not
large. The nonlinearity of the vehicle suspension is not included in the current study, this
is the limitation of this vehicle dynamic model, and it will be considered in the coming