Abstract: This paper investigates the dynamic behavior of half vehicles with a passive suspension system. The study uses an improved pseudo-random road excitation method that has been proposed as a type of road input excitation for vehicles in shock mitigation. For this, five motion equations of the half vehicle model are established, which are derived in terms of four displacements and a pitch angle. Based on the principle of analog equation, the new direct time integration method is used for numerical integration. Both the power spectrum density (PSD) in frequency-domain and the vehicle dynamic response in time-domain against two types of road inputs are investigated and simulated. This includes the PSD of driver vertical acceleration, chassis (vehicle body) vertical acceleration, front (rear) suspension dynamic deflection, front (rear) dynamic tire load, and response of displacement and velocity. The simulation results are achieved for different type of initial inputs. Finally, the value of the specific frequency point of power spectrum density and the time-domain dynamic response of the model are obtained, and the reasons are analyzed.

Key words: improved pseudo-excitation method, passive suspension system, direct time integration method, power spectrum density