Using the same device and method as the report 2, relation between the side force and the side slip angle of wheel with yaw angle was studied. In this report, especially, fundamental side slip angle of wheel was introduced, which was the side slip angle with no slippage. And relation of the fundamental side slip angle to the transformed side forth was more linearized than the side slip angle.
The slippage of wheel was caused by the resultant force of traction force and side force. But the side force was multiplied by the ratio of minor to major axes of the friction ellipse in length that denoted the frictional resistance of tire.
On the slope field, suppose the effect of the steering angle of front wheel, calculate lateral and longitudinal forces of wheels, and the running state of tractor can be analized. Fig. 9 shows the yaw angle (α) of tractor and the steering angle (δ) of front wheel, moving along the contour line of the slope field.