Abstract: Stability criterion for the vehicle under critical driving situation is the base of vehicle stability control system, it decides the intervention time for the stability control system. Based on 2 degree of freedom linear vehicle model, select the four criterions that are yaw rate method, lateral acceleration method, independent steering gradient method, and turning radius method. Based on nonlinear vehicle model, sideslip angle-sideslip angle speed phase plane method is selected to analyze the vehicle stability, and the study proposes an improved diamond method with five parameters to determine the stable region. With tire force method as the standard, the five criterions have been validated and compared in several simulation manoeuvres on the Carsim & Matlab/Simulink co-simulation platform for their timing and accuracy. It is found that there are significant differences in the effect of the criterions. Among them, the yaw rate method, the turning radius method, and the improved diamond method with five parameters have high accuracy and are relatively complemented.

Key words: critical driving situation, evaluate, model based method, phase plane method, stability criterion