Research On Lateral Stability Control Strategy For Vehicles With The Brake-by-Wire System

The brake-by-wire system has the advantages of precise braking force allocation and fast response speed,which is in line with the long-term development vision of safety,energy saving,environmental protection and comfort in the automotive industry.So it is expected to replace the traditional hydraulic brake system in the future,and has great research significance and broad market prospects.At the same time,because the four-wheel braking force can be independently distributed,and the actuator’s degree of freedom is greatly improved,if the traditional vehicle stability control strategy is still used,the advantages of the brake-by-wire system and the potential of vehicle dynamics cannot be fully utilized.Therefore,in order to improve this shortcoming and promote the development of the brake-by-wire system,it is necessary to research the new vehicle stability control strategy and method,which is suitable for the brake-by-wire vehicle.In this paper,the stability control of vehicle with the brake-by-wire system is studied,and the main contents are as follows:First,vehicle dynamics model,tire model and actuator math model of the brake-by-wire system are established,and the magic tire model is optimized for the joint slip condition,which is more in line with the tire in the actual driving process.Vehicle’s lateral stability and instability reasons under high-speed extreme conditions are analyzed theoretically,and the vehicle instability judgment method based on the yaw rate’s threshold deviation and phase plane method of side slip angle is designed.Next,aiming at the current problems in the estimation of the side slip angle,the variable structure extended Kalman filter(VEKF)algorithm is designed.This algorithm can improve the robustness to multi-source sensor noises and reference model errors by fusing the direct integration method and the model-based method.Then,the co-simulation test platform based on Car Sim/Simulink and real vehicle test platform are built,the verification results under various typical test conditions show that the designed observer has good accuracy and robustness.Last,the new type of vehicle lateral stability control system is designed.The upper additional yaw moment controller adopts the feedforward-feedback control method,and the feedback controller adopts an LQR linear quadratic regulator with adaptive adjustment of the weight coefficient,which can resist the influence of system parameter perturbation and the change of road attachment conditions;the lower-level torque distribution controller adopts an optimal control distribution method to realize the four-wheel braking force’s independent optimal allocation.The co-simulation test results prove that: compared with the traditional vehicle stability control system,the designed lateral control stability algorithm can effectively improve the vehicle lateral stability especially under high-speed extreme driving conditions,which give full play to the advantages of the brake-bywire system and the potential of vehicle dynamics,and have a good engineering application prospect.