考虑车身侧倾的4WS汽车横向稳定性与Hopf分岔特性

四轮转向汽车与传统前轮转向相比,能增加车辆高速行驶稳定性和低速转向灵敏性。车身侧倾时轮荷转移会改变轮胎侧偏特性,从而影响4WS汽车横向稳定性及分岔特性,为此研究了考虑车身与底盘的非线性耦合,建立了考虑车身侧倾时轮荷转移的3-DOF闭环系统动力学模型,先定性判定系统Hopf分岔存在性与稳定性,再运用数值方法计算系统的稳定区域与Hopf分岔特性。并与2-DOF闭环系统平面模型对比,结果表明,2种模型计算结果有明显区别。对于3-DOF系统,随着预瞄距离、前后轮转角比例系数的增大,系统稳定区域会增大;随着前后轮转角比例系数的增大,汽车侧倾角、侧倾角速度的自激振动极限环幅值呈减小的趋势。

Lateral Stability and Hopf Bifurcation Characteristics of 4WS Vehicle Considering Body Roll 4WS Vehicle Considering Body Roll

Compared with traditional front-wheel-steering system, the four-wheel-steering system can improve the auto handing stability at high speed as well as the steering response at low speed. Load transfer caused by the body roll can change the tyre cornering characteristics as well as the lateral stability and the bifurcation characteristics of the 4WS vehicles. Therefore, a closed loop system dynamic model considering load transfer was established with the nonlinear coupling relationship between the body and chassis taken into account. Firstly, the existence and stability of the Hopf bifurcation were qualitatively analyzed, then it was compared with a closed loop system dynamic model, the stable region and the characteristics of the Hopf bifurcation were calculated by numerical methods. The results showed that the difference between two dynamic models was obvious. For the 3-DOF system, with the increase of preview distance, steering ratio, road adhesion coefficient and the decrease of the height of suspension roll center, the stable region of the system tended to increase. With the increase of road adhesion coefficient and the steering ratio, the amplitude of self-excited vibration of roll angle and roll angular velocity tended to decrease.