Research On Key Technology Of Active Collision Avoidance Braking System Based On Pavement Identification

With the rapid development of automobile industry,the number of vehicles is increasing,and the traffic safety problem is becoming more and more serious.In recent years,with the development of electronic control technology,the research of intelligent vehicle has become a hot spot.As the most important active safety technology,active collision avoidance system has been paid more and more attention.But only rely on spatial information on braking and steering actuator and control decision-making will trigger a series of security problems,especially common in the harsh environment under the condition of the vehicle rear end,sideslip and traffic accidents are due to the lack of information led to road conditions braking force control is not accurate.In view of this problem,this paper will combine the requirements of active collision avoidance system,identify pavement information,and improve the braking system program.First of all,analyzing the research results of road identification and braking system of the current.It is proposed that the road condition is the main factor that restricts the braking force,and according to the active collision avoidance system the anti-lock braking system is designed based on the road surface identification.According to the peak adhesion coefficient of road surface,the braking pressure is calculated as the threshold value,and the direct control is achieved when the anti-lock condition is achieved.Secondly,the first step to realize the braking scheme is pavement identification.Based on the research of Burckhardt tire-road mathematical model,the identification algorithm of the peak adhesion coefficient is designed.Considering the validity of the theory,the simulation of several typical pavement based on Burckhardt model is carried out in Simulink firstly.The vehicle simulation software is used as vehicle and road input,Simulink is combined with simulation,and the simulation accuracy is improved.And then use CarSim vehicle dynamics simulation software as vehicle and road input,and Simulink joint simulation,improve the accuracy of simulation.The results show that the algorithm has high precision and real-time performance.It issuitable for any road surface with typical pavement and is equally effective for variable road surface.Further more,the pressure control of the braking system is studied.The existing electronic control hydraulic system(EHB)used a high-speed on-off valve,which can not be controlled directly when the brake pressure is controlled,in the anti-lock process through continuous pressurization decompression.In order to facilitate the accurate control of the braking force during the collision avoidance,the EHB system is improved by the proportional valve,and the simulation model of the wheel cylinder pressure in the decompression and decompression process is established.In order to quickly and accurately control the brake pressure,a single neuron PID pressure controller is designed.The simulation results show that the response speed is fast and the dynamic tracking effect is good and there is no steady state error.Finally,In order to further verify the effectiveness of the braking system,through the CarSim/Simulink simulation,compared with the traditional ABS.Taking into account the difference between the hydraulic system of the braking process,only the two braking schemes require the maximum braking force.The simulation results show that the braking system designed in this paper is superior to the traditional ABS system,especially in the different road surface,which shows better braking performance.Solved the status of traditional ABS braking distance in poor road surface increases,the maximum braking distance can be reduced by 16%.