The objective of this paper is to enhance the accuracy of tire model combined tire cornering and braking forces with anisotropic tread and carcass stiffness. The difference of tire longitudinal slip stiffness and cornering stiffness will arouse that the direction of tire resultant shear stress in adhesion region is not the same as that in sliding region. Then the direction of total friction force in the whole tire-road contact patch will change under different combined cornering/braking situations.
Generally speaking, there is a basic premise: “the direction of resultant shear stress in sliding region will be the same as that in adhesion region” in the existing tire models, in which the anisotropy of tread and carcass stiffness is neglected. Therefore, these models don't work well when the tire tread and carcass stiffness has a strong anisotropy.
The direction of tire shear stress in the adhesion and the sliding region of the contact patch is discussed in this paper and a modification factor is proposed basing on the UniTire semi-physical model to modify the direction of resultant shear stress, which can describe the variation tendency of the total friction force direction in the tire-road contact patch with different combination of cornering and braking conditions. Finally, the UniTire semi-physical tire model contained modification factor is validated by the experimental data, which indicates the accuracy of combined tire forces has been enhanced significantly.
