针对客车快速转弯或变道过急等急转工况易发生侧滑或侧翻等问题，提出采用横向力系数作为客车急转工况下转向稳定的评估指标，推导考虑悬架的横向力系数计算式; 通过分析横向力系数对行驶稳定性的影响，定义了客车急转工况下横向力系数的预警阈值、危险阈值及其与车速的关系; 面向主动安全控制，提出基于横向力系数阈值的转向稳定的转弯半径计算模型，选取典型客车参数，采用对比分析法对计算模型进行仿真验证，模型所得结果正确有效，与IPG TruckMaker 所得极限值接近，并具有1． 15 ～ 1． 30 倍安全系数． 研究结果可为客车急转工况下的转向稳定评估及主动控制提供理论参考．

In order to avoid the sideslip or rollover under extreme turn conditions of bus with fast turning or too fast changing,first,a formula to calculate the lateral force coefficient considering the suspension movement effect is deduced by using the lateral force coefficient as an evaluation index of cornering stability under extreme turn conditions.Next,by analyzing the influence of the lateral force coefficient on the driving stability,the early warning threshold and the risk threshold of the lateral force coefficient under extreme turn conditions are both defined,and the relationship between the two thresholds and the vehicle speed is reveled.Then,in order to implement the active safety control of steering stability,a turning radius calculation model of cornering stability based on the lateral force coefficient threshold under extreme turn conditions is put forward.The proposed calculation model is finally verified through a comparative analysis by selecting some typical bus parameters.The results show that the calculation model is correct and effective,and that it helps to obtain a turning radius with a safety factor of 1. 15 to 1. 3,which is close to the limit value obtained by the simulation software IPG TruckMaker.This research provides a theoretical foundation for the cornering stability evaluation and active safety control of bus under extreme turn conditions.