Mathematical Model for Evaluating Slippage of Tractor Under Various Field Conditions

The slippage is an essential criterion for evaluating the fuel consumption and the field performance of tractor. The objective of this research was to develop mathematical models using Design Expert software for modelling and predicting slippage of the CASE JX75T tractor (India manufacture) under operational field conditions. In this research, a chisel plough was used as a loading tool for the tractor under four levels of ploughing depths, with three levels of speed and two levels of cone index (CI) in silty clay soil texture. The experiments were carried out in the site of Basrah University. The results obtained from the fieldwork were analysed to evolve mathematical models and equations to predict and evaluate the performance of the tractor when the slippage occurred. According to the obtained results, the single effects of the parameters (CI, tillage depth, and forward speed) on the slippage were highly considerable (P<0.0001). Moreover, the interaction of the parameters were significant (p<0.05). The slippage of tractor increased by 187 and 116 % with increasing ploughing depth up to 25 cm and forward speed up to 1.53 m.s-1, respectively. On the other hand, tractor slippage reduced by 34% when CI increased up to 980 kPa. The data analysis showed that the developed model has passable imitation ability and excellently executed in confront of the actual data. This confirms the accuracy of the model for predicting tractor slippage under different fieldworks.