Understanding the Effects of a Discrete Element Soil Model's Parameters on Ground Vehicle Mobility

Abstract

The Army's mission is to develop, integrate, and sustain the right technology solution for all manned and unmanned ground vehicles, and mobility is a key requirement for all ground vehicles. Mobility focuses on ground vehicles' capabilities that enable them to be deployable worldwide, operationally mobile in all environments, and protected from symmetrical and asymmetrical threats. In order for military ground vehicles to operate in any combat zone, mobility on off-road terrains should be extensively investigated. Mobility on off-road terrains is poorly understood because of the empirical and semi-empirical height-field based methods which are often used for predicting vehicle mobility, such as Bekker–Wong type models. Those methods do not capture the three-dimensional soil deformation/flow as well as the soil's nonlinear behavior. The discrete element method (DEM) in which soil is modeled using discrete particles was identified as a high-fidelity method that can capture the deformation of the soil and its nonlinear behavior. In this paper, a simulation study is undertaken to understand the influence of DEM soil model parameters on vehicle mobility. A typical wheeled vehicle model was built in ivress/dis software and simulated over different cohesive and noncohesive soils modeled using DEM, with a particular emphasis on weak soils (with both low friction angle and low cohesion). Some characteristics of these soils were varied, namely, the interparticle cohesion, the interparticle friction, the particle size, and the particle mass. The mobility measures, including vehicle speed, wheel sinkage, wheel slip, and tractive force were evaluated using the model and correlated to the DEM soil model parameters. This study shows that the vehicle speed increases with cohesion, friction, soil density, and particle size while wheel sinkage, wheel slip, and tractive force decrease with those parameters. The combined influence of those parameters is more complex. Extensive studies of those and other soil parameters need to be carried out in the future to understand their effect on vehicle mobility.