Estimation of tractor wheel slippage with different tire pressures for 4wd and 2wd driving systems

Abstract

The wheel slippage of agricultural tractors is a critical parameter for fuel consumption and field performance. Optimally it should be in the range of 8-12 % and should not exceed 15 %. Therefore, during assembling agricultural units, it is not enough to consider the traction characteristics, but also the recommended value of the slippage must be followed. Of the available solutions to decrease the tractor driving wheel slippage is to decrease the air pressure in the tires and increase the additional mass (ballast weight) of the tractor, avoid tilling soil that is too wet or too dry and choose the right implement, tillage speed and depth. The wheels’ slippage could be reduced with a traction control and other relevant tractor systems. Agricultural/field applications require tractors with 4WD or 2WD driving systems. Engaging the four-wheel drive, when using the tractor for tillage operations, also can decrease the wheel slippage. In any case, the fuel consumption must be taken into consideration. For the theoretical calculation of the optimal tractor wheel slippage it is important to know the attraction factor dependence on the size of the traction force and the vertical load on the tires and the tire pressure indicators as well. However, literature analysis shows that known tractor wheel slippage determination mathematical modules do not take into consideration the tire inflation pressure. The goal of this study is to investigate the tire air pressure influence on the driving wheel slippage, tractive force and the traction coefficient for 4WD and 2WD driving systems of the tractor. With help of mathematical equations the traction force and wheel slippage coefficient dependencies on the air pressure in tractor tires are calculated. As well, according to the research result data, the wheel slippage forecasting methodology based on the numerical evaluation of the tire inflation pressure for 4WD and 2WD driving systems of the tractor is provided.