Research On Emergence Brake Control Strategy Of Intelligent Vehicle Based On Braking By Wire

With the rapid development of intelligent car,the research on the key technology of chassis control system by wire has become a global development trend.At the same time,the continuous increase of car ownership has brought great convenience to people,but it also brings a lot of hidden dangers.Among them,rear-end collision is a relatively common traffic accident,causing different degrees of loss to people.Therefore,the critical control scheme braking by wire,pressure control technology and an emergency braking control strategy for the typical dangerous working conditions of autonomous vehicle emergency collision avoidance are proposed in this paper.Firstly,the intelligent vehicle platform,the structure of the intelligent vehicle and the overall plan of the AEB are introduced,an Integrated-Electro-Hydraulic Brake system(IEHB)scheme,which includes its composition,function and working principle,is proposed.The hydraulic system physical models such as master cylinder,wheel cylinder,hydraulic pressure pipelines,high speed switching valves,pumps motor etc by AMESim software,are established,and the open loop characteristics of the IEHB system are analyzed.In addition,the actuator of the IEHB system test platform is built,and the open-loop characteristics of the electric master cylinder-wheel cylinder of the IEHB system are calibrated,and the friction nonlinear problem existing in the pressure change is proposed.Secondly,the pressure control scheme of the electric master cylinder,the booster valve,the pressure reducing valve and the electric pump is proposed,through the analysis of the open-loop characteristics of the IEHB system.Due to the introduction of the electric master cylinder,the electro-hydraulic coupling characteristics of the solenoid valve and system characteristics large changes under different working conditions during pressure regulation,it is necessary to consider the integrated control of the electric master cylinder and key components in the hydraulic adjustment unit(HCU).According to the dynamic model of the solenoid valve,a wheel-cylinder pressure control strategy based on sliding mode variable structure method is proposed.Based on the experimental analysis,the wheel cylinder pressure control strategy with an auxiliary boosting the coefficient compensation of feedforward-feedback method,is proposed to realize the design of the wheel cylinder pressure controller of the IEHB system.Thirdly,aiming at the research on automatic emergency braking(AEBB)problem of self-driving cars,a new layered compensation control framework is selected.By considering the conditions of the preceding vehicle,road adhesion and vehicle braking process,etc,the risk assessment layer model based on the fuzzy rule method is built.By constructing the vehicle system model and the optimal slip rate estimation model,the slip ratio control layer model based on adaptive RBF network compensated sliding mode control method is built.For the I2EHB system,an average value allocation strategy is designed as the target pressure determination layer,and selecting the wheel cylinder pressure controller of the above designed as the execution layer.Finally,the Carsim/AMESim/Simulink co-simulation platform and the N1/PXI-dSPACE hardware-in-the-loop(HIL)platform based on actuator control by wire are established,The pressure control and emergency brake control scheme proposed in this paper are simulated and tested under different working conditions.The results show that the IEHB system pressure controller designed in this paper can achieve better pressure tracking.The emergency braking system can effectively realize the vertical emergency collision avoidance process while ensuring the stability of the self-driving car.