Lateral slope effect on tipping behavior of a tractor encountering an obstacle (model development)

A three-dimensional mathematical model of tractor on lateral slopes was developed in this study. The model considers the nonlinear geometric relationships of the arms of the ground supporting forces when the tractor passes over a half sine curve obstacle. It is subsequently ap-phcable to large rotations of a tractor. Meanwhile, the change of the direction of a supporting force due to the interaction between tractor pitch and roll motions and its result in corresponding tire deformation are the concern of this study. Given the transformation matrix, the tractor translations and rotational motions were observed in a global coordinate. According to the de-veloped model, one can obtain the tractor bounce displacement, the pitch angle, and the accel-eration characteristics. Furthermore, the supporting and lateral friction forces can be examined since they predominantly determine the tractor lateral rollover and sideslip which affect tractor safety to a great extent. Therefore, the lateral slope effect on these forces was investigated con-sidering a tractor speed of 0.5 m/s and an obstacle height of 0.08 m. Results showed that as the slope angle increases, both the supporting and lateral friction forces put the tractor to a situation closer to danger. In particular, a specific slope angle of 25' was highlighted as a warning parameter because the onset of rollover as well as tractor sideslip were discovered. It is also found that a tractor is more susceptible to sideslip than rollover along with the slope increasing.