Towards more efficient tractors: Assessing and refining traction test procedures for agricultural tractors

A reliable testing procedure is needed to benchmark different vehicle and tyre parameters. Several testing procedures within two main families – transient and steady states – were adopted to evaluate drawbar performance of tractors. The two procedural families were not hitherto compared using a full vehicle. This article aims to fill this gap. The transient and steady-state procedures were tested using a tractor rated of 230 kW sets in different configurations and equipped with sensors for evaluating the tractive parameters. In the transient procedure, the drawbar load was continuously increased to maintain a fixed ground speed. In the steady-state procedure, the drawbar load was gradually increased by reducing the ground speed. The maximum drawbar force generated by the tractor differed little between procedures, but a difference was observed in power delivery efficiency, mostly for the transmission’s influence during transient conditions leading to variable transmission efficiency. The results of the steady-state procedure for different vehicle configurations were more consistent with findings in the literature than those of the transient procedure. The steady-state procedure is better than the other but it requires more land and therefore it is less convenient when drawbar performances must be quickly evaluated for many vehicle and soil configurations.