A method of three-dimensional stability region and ideal roll angle to improve vehicle stability

The current research for the vehicle stability regions mainly focuses on the two-dimensional plane domain of yaw rate and sideslip angle, without considering the influence of body roll angle on vehicle stability performance. To improve the vehicle stability, in this study, based on the study of the spatial distribution of the unstable state, a method of determining the three-dimensional stability region of "lateral speed-yaw rate-roll angle" was proposed, the variation of the stability region with front steering angle was studied, and the limit steering angle boundary of several typical road conditions was obtained. Secondly, the minimum distance between the vehicle state point and the stability region was used to measure the vehicle stability, and the stable roll angle range and ideal roll angle under different speed and front steering angles were obtained. Finally, on high and low adhesion roads, the simulation comparisons of the vehicle stability under the ideal state trajectory and the two controllers were carried out. The results demonstrated that the higher the vehicle speed, the lower the road adhesion coefficient, which meant that the vehicle driving condition was worse; the trend of ideal roll angle moving against the original roll direction was more intense. At low speed, although the vehicle stability considering the ideal roll angle was improved, the stability without considering the roll angle could still meet the safety requirements. However, at high speed, the vehicle stability considering the ideal roll angle was significantly improved; especially when the vehicle was driving at high speed on a low adhesion road, the mean and minimum of the stability performance index corresponding to the ideal roll angle were increased by 23.89 and 50.16%, respectively.