Modification of a tractor dynamic model considering the rotatable front end

A mathematical model for tractor dynamics was expanded by considering the rotatable tractor front end. The fundamental shortcoming of the simplified model was revealed by the loss of contact of the tire with a rigid horizontal surface in an obstacle-passing case. Further shortcomings of the simplified model arise from aspects of the motion and vibration characteristics. The improved model provides a better and more realistic representation of the tire-ground contact condition and is applicable to tractors on lateral slopes. The independent roll motions of the two main tractor parts (the front end and main body) significantly reduce the motions of the tractor and thus increase its stability. Furthermore, the effects of the forward tractor speed and obstacle height were studied for a tractor on a 10° lateral slope. By analyzing the motion amplitude and tire-ground contact condition, the tractor speed and obstacle height parameters associated with danger and risk were evaluated. The results suggest the greater capability of the improved model to predict tractor dynamic response in Phase I overturn.