Interaction mechanics model for screw‐drive wheel of granary robot traveling on the loose grain terrain

The screw drive mechanism has excellent driving performance on soft terrain and it is a good application for granary robot traveling on the loose grain surface. The investigation on screw drive wheel‐terrain contact mechanics is necessary to predict the traveling performance of the novel Screw‐Drive Granary Robot. Because the motion of grain particles is extremely complex beneath the wheel in the space, shearing displacement is decomposed into the longitudinal and tangential shearing displacement in this paper, and the corresponding shearing stress is calculated separately. Then the screw‐drive wheel‐terrain contact mechanics theory based on terramechanics is established by integrating the normal stress and shearing stress. Through driving experiments on corn‐terrain, the slip sinkage is determined and the sinkage modeling is modified simultaneously considering both vertical load and slip to improve the accuracy of prediction. And the calculated total resistance and the bulldozing resistance show that there is a linear proportional coefficient between them and slope of the line is 2.74 in this case. Finally, the improved mathematical model for screw‐drive wheel is proposed, the average error of predicted resistive torque is 15.72% and the mean error of drawbar pull is 16.2%.