Research on UniTire steady-state sideslip turn-slip combined semi-empirical tire model

Simulation technology and driving simulator applications serve as crucial means to shorten development cycles and reduce costs for new vehicle models. To meet the demands of vehicle dynamics simulation across multiple scenarios, further refinement and in-depth research on tire models capable of characterizing turn-slip mechanical behavior are essential. As current mainstream A-frame tire test rigs lack the capability to evaluate steady-state turn-slip mechanical properties, this paper proposes a finite element simulation method for steady-state combined sideslip and turn-slip conditions. Based on the simulation results and a discrete theoretical tire model, the influence of sideslip angle and turn-slip ratio on the steady-state mechanical behavior under combined conditions is investigated. Within the fundamental framework of the UniTire model, a steady-state semi-empirical tire model for combined sideslip and turn-slip conditions is developed. First, a finite element tire model is established using mass-production tire design and test data, and its simulation accuracy is validated against static stiffness and quasi-static sideslip test results. Second, the discrete theoretical tire model is employed to extend the representation range of sideslip angles and turn-slip ratios under steady-state combined conditions, analyzing the effects of sideslip angle on turn-slip lateral force and turn-slip ratio on sideslip aligning torque. Furthermore, theoretical derivations for modeling lateral force and aligning torque under steady-state sideslip and turn-slip combined conditions are conducted based on the UniTire semi-empirical sideslip model framework. Finally, the steady-state UniTire semi-empirical model for combined sideslip and turn-slip conditions is developed, and its fitting accuracy against finite element simulation results is compared with that of the PAC2002 model. The results demonstrate that the proposed UniTire model achieves average improvements of 7% in lateral force fitting accuracy and 6% in aligning torque fitting accuracy compared to the PAC2002 model.