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This paper presents a six degree of freedom full vehicle model simulating the testing of heavy truck suspensions to evaluate the ride comfort and stability using actual characteristics of gas charged single tube shock absorbers. The model is developed using one of the commercial multi-body dynamics software packages, ADAMS. The model incorporates all sources of compliance: stiffness and damping with linear and non-linear characteristics. The front and the rear springs and dampers representing the suspension system were attached between the axles and the vehicle body. The front and the rear axles were attached to a wheel spindle assembly, which in turn was attached to the irregular drum wheel, simulating the road profile irregularities. As a result of the drum rotation, sudden vertical movements were induced in the vehicle suspension, due to the bumps and rebounds, thus simulating the road profile.

This paper investigates the effect of tire inflation pressure on the directional stability of All Wheel Drive (AWD) vehicles during high-speed off-road maneuvers over different soft terrains such as loam, sand and clay. For this purpose, a fourteen-degrees-of-freedom (14-DOF) full parametrized vehicle model is employed and numerically simulated in MATLAB/Simulink environment to represent the full vehicle body dynamics such as roll, yaw and pitch motions. In order to calculate tire forces and moments over deformable terrains, the AS2TM Soft Soil Tire Model was successfully integrated with the vehicle model which enabled the possibility of changing tire pressure and consequently investigate its effect on vehicle dynamics. Numerous simulations are carried out to examine vehicle handling in case of different tires inflation pressure during steady state turning maneuvers such as ramp steer input.