极限工况下周期转向汽车侧向动力稳定性及分岔分析

将汽车在极限工况下的转向操作建模为周期转向激励的非线性振动系统的响应,结合打靶法和Floquet理论分析了周期转向的稳定性和分岔行为.应用Poincare映射分析了不同的质心位置和不同的车速对极限工况下汽车转向频率特性的影响.结果表明,汽车周期转向时可能发生鞍结分岔和倍周期分岔,发生鞍结分岔还常伴有跳跃现象;极限工况下汽车的转向频率特性与常规工况有很大的不同,转向频率对汽车的稳定性有显著影响,必须采用非线性分析方法.

Analysis on Lateral Dynamic Stability and Bifurcation of Vehicle Periodic Steering under Critical Condition

The vehicle steering manoeuver in critical conditions was modeled as the response of a nonlinear vibration system with external periodic steering excitation.The stability and bifurcation behavior of the periodic steering motion were analyzed with shooting method and Floquet theory.By using Poincare mapping, the influences of cg position and vehicle velocity on steering frequency behaviors under critical condition were analyzed.The result shows that (1) saddle-node bifurcation and periodic bifurcation may be found when steering periodically under critical condition and jumping phenomenon often follows saddle-node bifurcation; (2) the steering frequency behavior has large differences under critical condition from that under ordinary condition.The steering frequency affects the vehicle stability significantly under critical condition, so the nonlinear analyzing method is necessary.