Modeling of wheel-soil interaction over rough terrain using the discrete element method

A numerical study was conducted using the discrete element method (DEM) to investigate the performance and mobility impacts of rough terrain operation for small unmanned ground vehicles. The DEM simulation was validated using experimental data from two types of single-wheel tests previously published in the literature: straight-line locomotion over flat, level soil, and wheel-digging. Results from the validation showed good qualitative agreement. Rough terrain was modeled using 20 sinusoidal profiles with varying frequency and amplitude. Straight-line single-wheel simulation test results for rough terrain showed decreases in mobility and efficiency compared to flat, level terrain. At low slip ratios average drawbar pull decreased as much as 15%, while driving torque increased as much as 35%. The frequency of the rough soil helped create oscillations in drawbar pull and driving torque, which significantly increased the span between minimum and maximum values. The impact of rough terrain was limited by the use of a low longitudinal velocity of 0.1 m/s and a soft lunar regolith simulant soil. Vertical accelerations that can lead to vehicle vibration, which have been shown to impact vehicle performance, were limited by the ease with which the wheel displaced soil. (C) 2013 ISTVS. Published by Elsevier Ltd. All rights reserved.