The Safety Study Of Heavy Vehicle Driving Downhill Basing On Engine Brake And Exhaust Brake

In recent years, our country’s road transportation industry and automotive markets havemade rapid progress. Heavy commercial vehicle and some transport equipments have comeinto each field of transportation sector. All of that have greatly contributed to nationaleconomic development, but the driving safety of heavy trucks cannot be ignored, especially inlong and great downhill path in mountain area. The reason for this is that the driver useservice brake frequently that causing brake overheating and loss brake effect. In order topromote the driving safety, continuous brake system is designed for the heavy commercialvehicle. The working principles and progresses of continuous brake are analyzed and studiedin the paper and the ability of automobile driving down slope is evaluated through bothexperimental and simulation methods to discuss the driving safety when the automobile goesdownhill.A heavy commercial automobile is chosen as the researching and experimental object.Study the ways about automobile’s driving downhill under the engine brake and exhaustbrake patterns, according to the result, evaluate the safety of driving the real road. This studybased on the test, first driving the heavy automobile without into the gears. The experimentaldata of velocity and time can be got from the tests. Using the method of least-squares and theknowledge of vehicle system dynamics to build the mathematical model of engine brake andexhaust brake and then build the model of the automobile driving downhill. Through thismodel the relation between steady speeds and slopes, the distance and speeds, speeds and timecan be known. To validate the accuracy the model, design the real ramps test. The result of thereal road test compared with the numerical simulation find the error is small, which validatedthe accuracy of this model. According the model can analyze the brake characteristics withdifferent gears and ability of automobile driving down slope. The driving patterns in differentcertain velocity and slopes were analyzed based on the results of simulations. Finally theassociated driving safety of the vehicle is appraised based on the highway design criteria.These research results have important theoretical and practical value on highway designand construction, and provide the instruction for drivers who often drive the heavycommercial vehicles on the long and great downhill path.