Influence of Tire-Individual Traction Parameters on the Chassis Efficiency of a Standard Tractor

Achieving traction for soil cultivation is one of the central tasks of a tractor.
Independent of the general drivetrain concept of the machine, the chassis efficiency contributes decisively to the energy-efficient use of a tractor. The tires play a major role as interface between drivetrain and soil.
Even in a drivetrain designed to be systemically efficient, e.g., by using differential locks and all-wheel drive, the tractive efficiency of each tire has an outstanding influence on chassis efficiency. The optimum tractive efficiency of a tire depends on the soil surface.
The efficiency can be optimized via traction coefficient and tire capacity.
The application of the tractor, e.g., plowing in the furrow, can result in different efficiency optimums for each individual tire.
In order to always achieve the ideal chassis efficiency, the optimum operating points on the tire-individual efficiency characteristics must be found.

This thesis investigates several influences of drivetrain and tire settings on chassis efficiency. For this purpose, a simulation model of the drivetrain of a standard tractor is built, which uses an empirical traction model known from the literature to describe the tire-soil contact. Based on the findings in published studies, the traction model is adapted for the model parameters motion resistance and multi-pass effect. From the results of the simulation model, recommended settings for drivetrain and tires are derived to achieve the optimum chassis efficiency.
Field measurements are executed to verify selected recommendations. For this purpose a standard tractor is equipped with wheel force and torque sensors on all four tires to determine the tire-soil mappings of each wheel.