The Research Of Vehicle Stability Based On Electro-hydraulic Brake System

In recent years, electro-hydraulic brake (EHB) system becomes a research focus of the field ofvehicle active safety due to its advantages, such as large brake pressure, fast response, easy to control,and prone to meet the performance reqiurements of ABS, ASR and ESP systems.In this paper, the dynamic characteristics of EHB system are analyzed and some stability controlstrategies for vehicles with EHB system are presented, including longitudinal stability, yaw stabilityand roll stability. Also, to prevent vehicle rollover and improve yaw stability when vehicle incornering at high-speed, some control methods are applied to simulate the joint performance on yawstability and roll stability.First, the dynamics of EHB system is studied by combined with software simulation andexperimental methods. From the working principle of EHB system, a simulation model is establishedby using AMESim software. And the key parameters’ influence on dynamic performance of the wheelcylinder pressure is analyzed from the model. Also, a test bench is built to verify the model of EHBsystem. A Freescale micro computer is used to design the controller for the system. Then someexperiments are carried out and the results verify the correctness of the simulation model.Secondly, a co-simulation method is used to simulate dynamic performance of vehicle with EHBsystem, including longitudinal stability, yaw stability and roll stability. According to the theory ofvehicle stability, eight degrees of freedom nonlinear model is established by using Simulink software.The whole vehicle model is obtained by combined the vehicle model with AMESim model of EHBsystem. Then PID control strategy is designed to study longitudinal stability based on the wheel slipratio. The fuzzy control strategy is designed to maintain vehicle yaw stability by using differentialbraking method. To prevent vehicle rollover, robust control method is designed to control the lateralload transfer ratio (LTR) within a reasonable range of values.Finally, multi-objective stability control strategy is designed to simulate the joint performance onyaw stability and rollover stability. The LQR algorithm and the weighted linear algorithm are used tokeep LTR and the yaw rate within the scope of the reasonable range when vehicle moves in corneringat high-speed. The results show that EHB system can not only enhance the vehicle longitudinalstability, also can improve yaw stability and prevent the vehicle rollover.