The mechanism of vehicle dynamics steering bifurcation has almost been confirmed. But the present steering bifurcation mechanism cannot explain the bifurcation phenomena caused by the driving torque. As a result, the vehicle coupled bifurcation analysis of the steering angle and driving torque has not been studied. Based on the five degrees of freedom (5DOF) vehicle system dynamics model with driving torque involved, the vehicle dynamics equilibriums under different driving torque and driving mode were searched by a hybrid method in this paper. The hybrid method combined the real-coded Genetic Algorithm with Quasi-Newton gradient method. According to the definition of static bifurcation of nonlinear systems, the equilibrium bifurcation of 5DOF vehicle system was confirmed. Then, the 5DOF vehicle system model was transformed into autonomous equation with the front wheel steering angle as intermediate variable. From the two aspects of constant steering angle amplitude and constant driving torque, the bifurcation diagrams of different driving mode were calculated. The vehicle coupled bifurcation characteristics of steering angle and driving torque were analyzed. The results show that the values of the driving torque will directly affect the bifurcation characteristics of vehicle dynamics system. The coupled feature of the front wheel steering angle and driving torque effect on vehicle bifurcation is obvious.

车辆动力学转向分叉的机理几乎已得到确认。但是，目前的转向分叉机构不能解释由驱动扭矩引起的分叉现象。结果，尚未研究转向角和驱动扭矩的车辆耦合分叉分析。基于五自由度（5DOF）涉及驱动转矩的车辆系统动力学模型，采用混合方法搜索了不同驱动转矩和驱动方式下的车辆动力学平衡。该混合方法将实数编码遗传算法与拟牛顿梯度法相结合。根据非线性系统静态分叉的定义，确定了五自由度车辆系统的平衡分叉。然后，将5DOF车辆系统模型转化为以前轮转向角为中间变量的自治方程。从恒定转向角幅值和恒定驱动转矩两个方面，计算了不同驱动方式的分叉图。分析了车辆转向角和驱动扭矩的分叉特性。结果表明，驱动扭矩的值将直接影响车辆动力学系统的分叉特性。前轮转向角和驱动扭矩对车辆分叉的影响是显而易见的。分析了车辆转向角和驱动扭矩的分叉特性。结果表明，驱动扭矩的值将直接影响车辆动力学系统的分叉特性。前轮转向角和驱动扭矩对车辆分叉的影响是显而易见的。分析了车辆转向角和驱动扭矩的分叉特性。结果表明，驱动扭矩的值将直接影响车辆动力学系统的分叉特性。前轮转向角和驱动扭矩对车辆分叉的影响是显而易见的。