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This paper discusses the development of a novel deformable terrain database and its use in a co-simulation environment with a multibody dynamics vehicle model. The implementation of the model includes a general tire-terrain traction model which is modular to allow for any type of tire model that supports the Standard Tire Interface[1] to operate on the terrain. This allows arbitrarily complex tire geometry to be used, which typically has a large impact on the mobility performance of vehicles operating on deformable terrains. However, this gain in generality comes at the cost that popular analytical pressure-sinkage terramechanics models cannot be used to find the normal pressure and shear stress of the contact patch. Pressure and shear stress are approximated by combining the contributions from tire normal forces, shear stresses and bulldozing forces due to soil rutting.

The use of virtual prototyping early in the design stage of a product has gained popularity due to reduced cost and time to market. The state of the art in vehicle simulation has reached a level where full vehicles are analyzed through simulation but major difficulties continue to be present in interfacing the vehicle model with accurate powertrain models and in developing adequate formulations for the contact between tire and terrain (specifically, scenarios such as tire sliding on ice and rolling on sand or other very deformable surfaces). The proposed work focuses on developing a ground vehicle simulation capability by combining several third party packages for vehicle simulation, tire simulation, and powertrain simulation. The long-term goal of this project consists in promoting the Digital Car idea through the development of a reliable and robust simulation capability that will enhance the understanding and control of off-road vehicle performance.

The purpose of this study is to improve predicted tire forces for vehicle simulations on off-road terrain and for simulations incorporating terrain features such as curbs, pavement markers or potholes. The model presented in this paper describes the longitudinal behavior of the tire for traversing high-fidelity terrain profiles. An extended rolling radial-interradial tire model is used to estimate the pressure distribution of the tire contact patch, while a tangential spring model of the tire carcass is used to estimate tractive forces at the tire/road interface. Due to the complexity of the model real-time simulation is not possible, however it is useful for off-line simulations incorporating rough terrain or short-wavelength terrain features.