Development Of Auxiliary Braking Simulation System For Heavy-duty Trucks

In recent years,the heavy-duty truck has commonly encountered major traffic accidents caused by brake failure on long and downhill sections of mountain roads.The continuous use of the service brake system has some potential safety risks,therefore,the auxiliary braking system is often used in the process of downhill braking.However,it is difficult to use and match the auxiliary braking system in long and downhill sections.This paper mainly analyzes the control rules of exhaust brake and hydraulic retarder when heavy trucks are driving downhill on roads with different slopes,and provides a basis for the development of auxiliary braking system when heavy trucks are braking downhill.This paper firstly discusses the research status of domestic and abroad auxiliary brake system.Then engine auxiliary braking system,eddy current retarder and hydraulic retarder is briefly summarized.On this basis,the braking performance and application status of each auxiliary braking system are compared and analyzed.Finally,the research content of this paper is determined.The braking characteristics of exhaust brake and hydraulic retarder are analyzed.Based on the theoretical mathematical model of engine exhaust braking,the braking characteristics are derived,and an exhaust braking model was built in Matlab/Simulink software.According to the hydraulic calculation method and the similar calculation method,the brake torque calculation model of the hydraulic retarder is derived.The braking model of the hydraulic retarder under the fixed gear is built by the gas-liquid stratification method,and the simulation model of the constant-speed control strategy of the hydraulic retarder is built by the Simulink/Stateflow module.The matching model of vehicle and auxiliary braking system is established.Firstly,the longitudinal dynamic analysis of the vehicle braking on a ramp is performed,and the force of the vehicle and the driving wheel under the action of the auxiliary braking system is studied.Then the model of vehicle deceleration running downhill is established and the matching model of the auxiliary braking system of the engine exhaust brake,the hydraulic retarder brake,and the combined brake are established when driving downhill at a constant speed.Finally,according to the GB12676-IIA experiment,the selection method of auxiliary braking system is put forward.Based on Truck Sim-Simulink software,a co-simulation model of the vehicle auxiliary braking system is established and the model is simulated and analyzed.According to the experiment of Type GB12676-IIA,the auxiliary braking system of a complete dump truck model in Truck Sim software was selected,and then a matching simulation model of the auxiliary braking system of engine exhaust braking,hydraulic retarder and the combined braking system was built.The condition of simulation is set and the average speed stipulated by the national standard is taken as the desired target stable vehicle speed,and then the simulation calculation of vehicle downhill braking under the participation of auxiliary braking system is carried out,finally the simulation result curve is analyzed.An auxiliary braking simulation system for heavy-duty truck is developed.Based on C# and SQL Server software,system login,parameter input,database management,and result output functions are implemented.This system is able to calculate the continuous speed of vehicles equipped with different auxiliary braking systems when driving downhill on different slopes.Finally,the reliability of the software is proved by comparing the calculation results with Truck Sim simulation results.