Research On Modeling And Braking Characteristics Of Air Braking System In A Train

Rail transit is the lifeblood of China’s national economic development and the backbone network of transportation.It plays an important role in solving the problems of passenger and cargo transportation,regional economic exchanges and urban traffic congestion.Vehicle braking system is one of key systems to ensure the operation safety of rolling stock.Especially with the increase of running speed and carrying capacity of rolling stock,the reliability and safety of vehicle braking system are required more strictly.Therefore,it is of great significance to study the braking system and braking characteristics of rolling stock.In the research of vehicle braking system and braking characteristics,theoretical calculation analysis,experimental simulation and numerical simulation are mainly used.The numerical simulation research can simulate the braking characteristics of vehicles in the complex climate environments and the complex track conditions among them.Compared with the experimental simulation methods and the theoretical calculation methods,the research cost is lower and the research efficiency is higher.However,the current researches on vehicle braking system simulation,braking system and vehicle system are still isolated,and lack of multi-system co-simulation analysis of vehicle,braking system and control strategy.Therefore,this thesis extends the isolated simulation study of braking system into multi-system cosimulation study to assess the adaptability of the braking system for the vehicle system and other issues.The main research work is as follows:Firstly,the compositions and braking modes of braking system of a certain EMU train were summarized.The Electro-pneumatic valve model,emergency valve model,load valve model and relay valve model were established on the AMESim simulation platform.Their pneumatical characteristics of each air brake valve were analyzed.According to the composition of the braking system,the Electro-pneumatic valve model,emergency valve model,load valve model and relay valve model were connected to establish the direct-airbrake system model.On the Simulink simulation platform,the electric brake model and the electro-pneumatic composite brake control model were established.The air brake system model was connected with the brake control model and the electric brake model through the co-simulation interface Simu Cosim to establish the electro-pneumatic composite brake system model of a certain EMU train.Secondly,the multi-body dynamics analysis software SIMPACK was used to establish the braking dynamics model of 2-motor 2-trailer power unit.In Simulink platform,brake dynamics model was connected with electro-pneumatic brake system via co-simulation interface Simat,and the train-braking dynamics model was controlled by the output braking torques computed by electro-pneumatic composite braking control system model.Based on vehicle braking system and braking dynamics model,the collaborative analysis platform was established.Finally,the collaborative analysis platform was used to study the braking characteristics of the 2-motor 2-trailer power unit braking dynamic model respectively when passing the linear section and the curve section under different braking grades.The volume of the brake cylinder and the cavity volume of Electropneumatic valve,relay valve in the braking system were changed respectively when passing the linear section under the maximum common braking grade to study braking characteristics and the effect of electric brake failure on braking characteristics.The research results show that:(1).the simulation results of the braking performance of the train are consistent with the operating characteristics of the braking system in the linear section and the curve section.Under the same braking grade,the braking distance and braking time in the curve section are correspondingly longer than that of the linear section.The derailment coefficients,wheel load reduction rates and lateral forces of axle in the curve section are obviously higher than that in the linear section.With the decrease of brake grade,the values of derailment coefficients,wheel load reduction rates and lateral forces of axle tend to increase.The longitudinal impact forces between two vehicles under emergence braking condition are larger than common braking condition.(2).With the increase of the braking system volumes,the charging and exhaust time of the braking cylinder are prolonged,the pressure amplitudes of the braking cylinder are reduced,and the braking distance and braking time are increased,the change rates of the braking deceleration speed is gradually reduced,and the derailment coefficients,wheel load reduction rates and lateral forces of axle are increased.The longitudinal impact forces between two vehicles are decreased with the increase of the volumes of the Electro-pneumatic valve and the relay valve,and the longitudinal impact forces are increased with the increase of the volumes of the brake cylinder.Compared with electro-pneumatic compound braking,the braking cylinder pressures increase,the braking time and braking distance are shortened,and the derailment coefficients,wheel load reduction rates and lateral forces of axle are nearly identical.But the longitudinal impact forces between two vehicles are obviously reduced.