Bekker's Terramechanics Model for Off-Road Vehicle Research

Abstract

Bekker's Derived Terramechanics Model (BDTM) is an analytical tool for evaluating vehicle off-road mobility. BDTM has been developed using Bekker's equations for vehicle soil interactions. He developed the bevameter technique to measure mechanical strength characteristics for many soil and snow conditions. This procedure uses seven parameters to describe soil conditions, which differs from the conventional single parameter vehicle cone index methodology used by the NATO Reference Mobility Model (NRMM). NRMM uses the cone penetrometer technique to experimentally measure fine- grained soil mechanical characteristics. BDTM is in a spreadsheet format, and its primary purpose is to compare mobility characteristics for robotic track and wheeled vehicles under different terrain conditions. Bekker's model is a simple, linear one degree-of-freedom (1-DOF) model, which assumes that in a perfectly cohesive soil (i.e. clay), soil thrust is only a function of contact surface area. The model also assumes that for a perfectly cohesionless or frictional soil (i.e. dry sand), soil thrust is a function of vehicular weight[1]. This paper attempts to compare the mobility characteristics of wheeled vs. track vehicles for different size, weight and terrain conditions.