Analysis of the Impact on Ride Comfort from Splitting the Unsprung Mass in Vehicle Modeling

The study was conducted to investigate the differences in ride comfort analysis between treating the unsprung mass as a whole and modeling it separately. A classical two-degree-of-freedom single-wheel vehicle vibration model and a three-degree-of-freedom single-wheel vehicle vibration model with split unsprung mass were established, with their state-space descriptions determined. The fundamental vibration response quantities of both models were identified, and time-domain simulations under random road excitation were performed using Matlab/Simulink. The results indicate that the two modeling approaches exhibit minimal differences in ride comfort analysis for the sprung mass, but there are certain differences for the unsprung mass. Additionally, for the three-degree-of-freedom single-wheel vehicle vibration model with split unsprung mass, the axle-to-wheel mass ratio was introduced to analyze the changes in the fundamental vibration response quantities when the unsprung mass increases by a fixed value and is distributed differently between the axle and the wheel. The results show that variations in the axle-to-wheel mass ratio have no significant impact on the vibration characteristics of the sprung mass. Reducing the mass ratio, i.e., transferring part of the unsprung mass to the wheel, can somewhat reduce the vertical acceleration of the unsprung mass, but it will slightly increase the relative dynamic load on the wheel.