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This paper presents a comprehensive approach for the mathematical and computer modeling of subsystems required in vehicle dynamic simulations. Three dimensional models for tire-terrain interaction, traction, braking, steering, and suspension systems are presented. The tire-terrain interaction model provides the necessary tire forces and moments which are determined by explicit formulation or experimental data based model. For the suspension subsystem, such elements as bushing, leaf spring, and stabilizer bar are reviewed. For the steering, traction, and braking subsystems, simplified models are discussed. The models developed here can easily be implemented in a three dimensional multibody simulation program.

This paper presents an analytical approach for a three dimensional tire model used for the steady-state simulations of vehicles. The functional relationship of slip ratios of the SAE definition and new definition suitable for vehicle dynamics analysis is first studied. New formula for friction is used and a contact pressure change is considered during driving/braking. The compliances of carcass, braker, and tread are employed for longitudinal and lateral elastic deformation. Rolling resistance force, plysteer, and conicity are also included in the explicit formulations of longitudinal force, lateral force, and aligning torque due to comprehensive slips.

An investigation of the effect of rack-housing rubber bushings on the handling characteristics of a vehicle is presented using a sophisticated three-dimensional vehicle model based on multibody dynamic analysis method. Previous research on this problem has been limited to a transfer function model for a simplified one- or two-dimensional steering subsystem. This paper uses a multibody modeling approach to find the effects of the steering-system compliance on the complete vehicle system. Sample simulations for circular cornering and pulse steering show that the steering-system compliance is the source of the frequency peak in the yaw rate to hand-wheel angle response function.

A tire longitudinal and lateral flexibility model has been developed which shows considerable advantages over the other available models or methods. Most of the available methods indirectly considers tire lateral flexibility effect by the inclusion of a time-lag function, whereas the developed model is a multibody representation of a wheel/tire subsystem so that the resultant dynamics are similar to those of an actual physical system. Sample simulations with a realistic three-dimensional vehicle model show the effectiveness of the developed model.