Research And Simulation Of Anti-Rollover Control Strategy For Vehicles

In recent years, as the rapid development of vehicle market in china, more and more car has come to Chinese people's eyesight. However, according to the survey made by NHTSA, car accidents are increasing every year correspondingly. Most car rollover accident occurred in higher center of mass cars such as SUV and the damage caused by car rollover ranking first in car accident. Thus, more and more researchers focus on this topic. At present, the research made by china in this field is in its infancy, so it's of great of importance for Chinese vehicle researchers to take the vehicle rollover research which can improve vehicle driving performance.Firstly, the main research target is settled. For vehicle anti-rollover control, the research needs a rollover stability evaluation. Based on the load transfer vehicle model, lateral load transfer ration (LTR) is presented. After considering various factors, the differential braking strategy is selected as the vehicle anti-rollover control strategy.Tire model determines the lateral force and braking force of vehicle dynamics model and a type of linear tire model is established in this thesis. Then, three degrees of freedom vehicle model is established based on ideal two degrees of freedom vehicle model. Thirdly, using SIMULINK to establish the vehicle model and tire model. Finally, four kinds of rollover test conditions is chosen as the front wheel angel input for simulation. The results show that the vehicle doesn't rollover when it's run at low and medium speed. But the vehicle is very likely to rollover when it run through the corner at high speed. Moreover, reducing the height of vehicle center or increasing the distance of tires can both effectively reduce the lateral load transfer ration, thereby reducing the probability of rollover.A detailed analysis of the principle of vehicle rollover differential braking is made and the analysis shows that reducing the vehicle longitudinal acceleration can effectively reducing the lateral load transfer rate. Because of the braking force at vehicle longitudinal direction, the three degrees of freedom vehicle model need to be changed to four degrees of freedom vehicle model. This model is also established in this thesis. Based on this model, a type of electro-mechanical brake mechanism (EMB) is designed and simplified as the form of transfer function.The traditional PID differential braking control strategy and the fuzzy adaptive PID differential braking control strategy is selected as anti-rollover control strategy of this thesis. Simulation contrast among uncontrolled vehicle, controlled with PID differential brake vehicle and controlled with fuzzy adaptive PID differential brake vehicle shows that differential braking control strategy can effectively prevent vehicle rollover, and fuzzy adaptive PID control is better than PID control.