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This paper presents a comprehensive testing of four different shock absorbers: three were passive and the other was readjust able to study their performance on vehicle ride and stability. For this purpose, a quarter vehicle model and a half vehicle model simulating vehicle suspension testing were devolved in non-dimensional form to study the effect of actual characteristics of shock absorbers on vehicle performance. The shock absorber characteristics were represented by the linear average value of shock absorber (both rebound and compression strokes), the linear rebound, and the compression strokes with different slopes and actual measurements characteristics. Also, a parametric study was carried out to study the effect of mass ratio and stiffness ratio on the vehicle performance. The mass ratio was defined as the ratio of the unsprung mass to the sprung mass while the stiffness ratio, was defined as the ratio of spring stiffness to tire stiffness.

To study vehicle dynamics, we need to know the forces and moments acting on the vehicle. The most important forces and moments acting on the vehicle are generated at the tire contact patch. A semi-empirical tire model was developed at Advanced Vehicle Dynamics Lab (AVDL) to use for vehicle simulations for steady-state conditions. In this paper, we extended that model to account for transient conditions. We present the basic concept, the development of the tire model, and selective simulation results. The transient tire model is developed by including the effects of the vertical load variations due to the velocity and the acceleration to the tire characteristic parameters. The simulation was performed for the semi-empirical transient tire model in two scenarios. The vehicle driving and braking maneuver was simulated to present the transient longitudinal tire behavior. The vehicle lane changing maneuver also was performed to present the transient lateral tire behavior.