A theoretical study of the parameters affecting the power delivery efficiency of an agricultural tractor

Abstract

Tractive efficiency is of major concern to agricultural tractors manufacturers, end-users and to society as well, both for economical and environmental reasons. In this article, a traction model of a whole vehicle is developed which accounts for the special features of a MFWD agricultural tractor. The aim of the article was to identify the key design parameters affecting the power delivery efficiency of an agricultural tractor and to quantify their effect on the tractive performance. To this end, numerical simulations were performed varying several tractor design parameters. The results of the simulations were then analysed using a gradient-based method which allowed to identify the most influential design parameters. A regression surface for the estimation of the tractive efficiency as a function of the relevant tractor design parameters was used to approximate the results of the numerical simulations and a quantitative relation to calculate the optimal mass distribution in terms of power delivery efficiency is proposed. Within the range of variation of the design parameters explored in this study, the maximum power delivery efficiency was found for a tractor having equal kinetic rolling radii of front and rear tyres, no lead of the front wheels and the centre of mass shifted towards the front axle. However, if the front tyres kinetic rolling radius becomes smaller than that of rear tyres and if there is lead of the front wheels, the tractor centre of mass has to be shifted towards the rear axle to attain the maximum overall traction efficiency.