Off-Road Traction Prediction for Wheeled Vehicles

Abstract

INTRODUCTION SOm-VEmCLE traction equations are an essential part of vehicle performance simulation. Man-controlled machine elements such as engines and transmissions have been understood and defined mathematically for a long time. Phenomena at the soil-wheel interface has not been as well understood. The dynamics portion of a simulation (Fig. 1) must include mathematical relations of wheel torque, speed, tractive force and slip. If an optimum machine configuration is to be selected by using simulation analysis, the traction relations must be sufficiently detailed to include variables such as tire section width, tire diameter, wheel load, and soil strength. Work at the Deere & Company Technical Center has led to the development of a series of simple but useful equations relating soil condition and tire characteristics to tractive performance. The equations have been developed for pneumatic tires with conventional tread designs and have been used as wheel-soil models in several detailed computer simulations of vehicles [1-3]. Programs have included an elevating scraper, agricultural tractor and log skidder. In addition, the equations are used in hand type analysis of less complicated problems such as tire sizing for agricultural implements.