稳定性是高速列车长期服役安全及推广海外首要保证问题之一。蛇行失稳不仅取决于自身参数，而且与运行外部条件有直接关系，已有相关实验和研究报道，但具体机理不详。近期研究表明，轨道不平顺对失稳速度有重要影响，但现有理论、实验方法均是基于确定稳定性理论，只能考虑无扰、小扰或先加激扰再去掉后运动是否收敛来判断。我们基于“蛇行失稳不是系统固有属性，而与外部运行条件相关，轨道激扰具有重要影响”这一假设，并以“怎样直接求解始终处于线路不平顺的轨道车辆失稳临界速度”这一问题为突破口。分别从轮对、构架、整车三个层面，利用非线性随机动力学Hamilton理论、蒙特卡洛法、半隐式Milstein随机数值模拟等方法，对随机稳定性、失稳后的分岔类型从理论分析、滚振实验、线路实验方面与现有方法进行分析比较，以此来验证我们的假设，并进一步揭示现有稳定性分析和实验方法的不足，以期为车辆失稳速度的求解提供新思路和新应用。

Running stability is one of the key performances that greatly affecting the long-term operation safety and overseas expansion of Chinese high speed trains. The hunting stability of rail vehicle is not only determined by the construction parameters, but also directly influenced by the operating environment, which has been verified by some field tests and research. But the mechanism of how the operating conditions affecting the hunting stability of rail vehicles is still unclear. Some recent research work shows that the track irregularity has significant influence on the hunting critical speed of rail vehicles. However, the existed theoretical and experimental algorithms on calculating hunting critical speed of rail vehicles are based on the definite stability theory, which only apply to the scenarios with smooth track, minimum track defect excitation or anterior partial track irregularity excitation. Based on the hypothesis of hunting stability being not the intrinsic characteristics of rail vehicle system, but mainly determined by the operating conditions and the track irregularity, this study is to develop a new direct solution algorithm for hunting critical speed of rail vehicle under track irregularity excitation. Three typical models with different levels of detail, including a signal wheelset model, bogie system dynamic model and the whole vehicle system dynamic model, will be established by using the Hamilton nonlinear stochastic dynamics theory, Monte Carlo method, semi-implicit Milstein stochastic approach. The stochastic stability and hunting bifurcation type of rail vehicles calculated using the proposed direct solution algorithm will be compared to that obtained by the existed theories, the roll rig tests and the field measurements, which will verify the new direct solution algorithm as well as reveal the deficiencies of the existing theoretical and experimental methods. The new solution algorithm will be useful in calculating the hunting critical speed of rail vehicles and applied to the design of new generation of Chinese high-speed train.