Research On Dynamic Characteristics And Pressure Delay Control Of Heavy Equipment Transporter Air Braking System

Heavy equipment transporters have gradually become an indispensable force in highway transportation industry because of their high loading quality and high transport efficiency.At the same time,due to the long body and high centroid,braking safety problem of heavy equipment transporters should not be neglected.Nowadays,pneumatic braking system is widely used in heavy equipment transporters.The compressibility of gas and long braking pipeline inevitably lead to the increase of braking response time and result in the occurrence of air pressure delay,which seriously restricts the braking performance of vehicles.In order to meet the requirement of national standard GB12676-2014 for the response time of the service brake system,it is necessary to theoretically analyze and effectively control the dynamic characteristics and the pneumatic delay phenomenon of the pneumatic brake system in heavy equipment transporters.Firstly,this paper takes the pneumatic braking system of heavy equipment transporter as the research object and elaborates the working principle of the braking system in detail.The braking system simulation model of heavy equipment transporter is established according to AMESim software.Through the simulation analysis of the braking system of the whole vehicle,it is concluded that the pressure response and mass flow change of the braking system model of the whole vehicle conform to the actual situation,and the pressure response of the semitrailer lags behind tractor,which restricts the braking performance of the semitrailer.Secondly,this paper designs and builds a pneumatic brake test bench for heavy equipment transporter to verify the accuracy of the main brake components.According to the national standard G B12676-2014,the brake response time of heavy equipment transporter is tested and evaluated.The experimental results show that the braking response time of tractor meets the regulation,while that of semitrailer exceeds the regulation.In order to further analyze the braking response time of semitrailer,a calculation method of response time is deduced by taking emergency relay valve of semi-trailer as an example,and the influencing factors of braking response time of semitrailer are analyzed by AMESim simulation model,which provides a theoretical basis for the control of subsequent response time.Thirdly,in order to reduce the braking response time of semitrailer,this paper modifies the braking system of semitrailer by adding solenoid valves.A PID control strategy optimized by genetic algorithm is designed to control the braking pressure in real time.The co-simulation results based on AMESim-Simulink show that the semitrailer response time is reduced to 0.352s,which indicates that the control strategy can effectively reduce the response time and improve the braking delay phenomenon.Finally,in order to solve the contradiction between pneumatic delay compensation and slip rate control,the control strategy of pneumatic delay compensation and slip rate coordination control is emphatically studied by using single-wheel vehicle model.The coordination control strategy is simulated and analyzed using AMESim-Simulink joint simulation platform.The results show that under the coordination control of air pressure delay compensation and slip rate,the chamber pressure increases rapidly and smoothly;slip rate did not show a large buffeting,which effectively avoids the occurrence of exhaust while inflating.It shows that the coordination control could improve the air pressure delay and ensure the control of slip rate which improve the braking performance of the vehicle to a certain extent.