四轮转向汽车的分岔与失稳分析

摘要

In order to analyze the four wheel steering vehicle＇s steering static bifurcation characteristics, a tyre model was adopted quadratic to set up the three degrees of freedom nonlinear dynamic model of the four-wheel steering vehicle. The stability characteristics in slippery road were analyzed by the nonlinear bifurcation theory and time-do- main simulations. The results demonstrate that compared with front wheel steering vehicle, the four-wheel steering vehicle＇s bifurcation can delay to appear, which enhances the vehicle steady-state cornering stability. It has been proved that not only Hopf bifurcation but high level equilibrium point bifurcation may appear, which will lead the vehicle out of control ultimately. The conclusion is useful for the system design of the four-wheel steering vehicle.%分析了四轮转向汽车稳态转向失稳的静态分岔特性。引入二次多项式平方轮胎模型，建立了四轮转向汽车的三自由度非线性动力学模型，应用非线性分岔和稳定性理论以及时域仿真对均匀路面工况的稳定性进行了分析，并与前轮转向汽车进行了对比。结果表明：四轮转向汽车相比前轮转向汽车，能允许更大的前轮转角输入，延缓了分岔的发生，提高了汽车的转向稳定性；随着车速和前轮转角的增加，四轮转向汽车奇异点处既可能发生高阶平衡点分岔，也可能会发生Hopf分岔，两种分岔均会导致汽车失稳。