New algorithms for predicting longitudinal motion resistance of wheels on dry sand

Abstract

Predicting the resisting forces against a vehicle's wheel during movement in loose sand is critical for optimizing tractive capabilities in desert regions, sand dunes, and beaches. We review existing braked, powered, and towed motion resistance equations and present improved algorithms based on field and laboratory measurements when the cone index is used to define soil strength. The algorithm predictions are compared against measured values available through Database Records for Off-road Vehicle Environments (DROVE), a database of tests conducted with wheeled vehicles. The examination of braked, towed, and powered motion resistance algorithms is considered for loads varying from 0.187 to 4.49 kN, tire diameters from 0.377 to 1.05 m, and soil strengths from 50 to 800 kPa. A simplified motion resistance algorithm was developed for each operation type utilizing a bootstrap technique. Simple relationships using wheel slip and the ratio of the contact pressure to the cone index are shown to provide predictions of motion resistance with accuracy comparable to more complex empirical models.