INVESTIGATING THE PARAMETERIZATION OF MAGIC FORMULA TIRE MODEL USING DATA FROM DYNAMIC TIRE-SOIL TESTS

摘要

Tire-soil performance attracts the attention of automotive and geotechnical engineers; the automotive engineer is interested in the traction of tires over soft terrain and the geotechnical engineer is concerned about the effect of the tire movement on soft terrain. Drawbar pull and the depth can characterize the tire tractive capability and the effect of the tire traffic on soil, respectively. In this paper we present results for soil properties tests and dynamic tire-soil tests. The experimental work was conducted using a Standard Reference Test Tire (SRTT) and loamy sand. During the soil properties test, gravimetric water content (GWC), cone index (CI), and bulk density were measured for the loamy sand at various levels of soil compaction. These measurement data were used to parameterize a bulk density estimation formula that enabled on-site evaluation of soil compaction using measurements of CI and volumetric water content (VWC). The soil physical parameters, the normal load, the tire inflation pressure, and the slip ratio were considered in the Design of Experiment (DOE) for the dynamic tire-soil test. The initial soil physical parameters of the loamy sand, the drawbar pull, and the rut depth were measured at various combinations of the parameter levels, per the DOE, in the dynamic tire-soil test. The influence of the inflation pressure on drawbar pull coefficient (DPC) and rut depth was analyzed. Based on the trend of the DPC versus longitudinal slip, the Magic Formula tire model (MFTM) was selected to be parameterized using a genetic algorithm (GA) and measurement data about the DP against slip ratio. The outcomes of this paper could be further used for extending the MFTM to other types of off-road conditions and for the development of novel off-road traction control systems.