A Study On Vehicle Transient Handling Performance Under Large Lateral Acceleration

Vehicle handling stability is one of the most important performance of modern cars. In recent years, domestic and foreign scholars have made a lot of research works on the vehicle handling stability, and has obtained certain research results. But most of these studies analyzed the influence factors and effects of vehicle handling stability from the perspective of steady-state handling stability. In fact, most driving time is in transient conditions, so it is difficult to meet the requirements of drivers on vehicle handling performance if we only do the research on steady-state handling stability. Especially with the improvement of the vehicle speed, people pay more and more attention to the transient handling performance under high speed and large lateral acceleration. Some explorations on vehicle transient handling performance under large lateral acceleration were done in this thesis.The thesis aimed at investigating the influencing theory and analyzing the effect of tire characteristics, suspension K&C characteristics and other quality parameters on the transient handling stability. Some reference opinions for research and improvement of the vehicle and tuning suspension were provided in the thesis.Specifically, the main contributions of this thesis are listed as follows:1, MF tire model was established. First of all, the basic theory of the "Magic Formula" tire model which put forward by the professor Pacejka was introduced in this paper. Second, the tire model code was written in Matlab software, and then tire model parameter identification which based on the tire test data was made. Lastly, the steady state tire model was completed, then, tire relaxation length was added in the steady state tire model, so transient tire model was built at Matlab/Simulink.2, The influence factors analysis of vehicle handling stability were studied. Some parameters of tire characteristics, suspension K&C characteristics, quality parameters and other parameters were introduced in this paper. Then, the influencing theory and mechanism of these parameters on the vehicle handling stability were studied. Also, the evaluation indexes of the transient handling stability were introduced in this paper.3, The vehicle handling performance under automotive steering transient conditions was studied. Fistly, the basic modeling knowledge of parametric modeling software Car Sim in automobile industry was introduced in this paper. And more important work was on the description about co-simulation method of Car Sim software and Matlab/Simulink. From the perspective of qualitative, the simulation analysis was carried out on the typical steering transient operating conditions, steering wheel angle step conditions and steering wheel angle pulse conditions. Then, the data processing and analytical work were done for simulation results refer to the national standard of vehicle handling stability. Based on the above methods, the studies that how the factors influence vehicle transient handling performance under large lateral acceleration were done in this thesis, the effects which include tire relaxation length, suspension roll stiffness, height and position of the center of the car, and so on.