Study On The Friendliness Of Vehicle-road Of Long And Steep Longitudinal Slope Section

There are many mountains in China. With the development of the highway, more and more highway are built in the mountain area, so a lot of the long and steep longitudinal slope are appeared. When the heavy truck travels on the section, it’s speed drops seriously, which has an influence on the traffic flow, increases the cost of transportation and even leads to traffic accident by overtaking of the following vehicles. The main reason lies in that the criterion of the grade and grade length is focused on the construction costs and environmental protection, while the cost of the transportation and the driving safety are insufficient considered. At the same time, the riding comfort is being a focus of attention. Therefore, comprehensively considering the behavior of human-vehicle-system should be the design direction of the steep and long longitudinal slope. In this paper, it is mainly researched that the characteristic of speed and the characteristic of the vertical acceleration of heavy truck at the section.Firstly, it is briefly described that the several classical methods of multi-body dynamic. At the same time, the setup method and solved method of the kinematics and dynamics equation in the system dynamics software ADAMS are also introduced.Secondly, based on the multi-body system dynamic theory and automobile dynamic theory, the model of 1+2+5 heavy truck is built, in which the process of modeling the key part of heavy truck are introduced in detail.Thirdly, the characteristic of climbing speed is studied by using the whole truck model in the ADAMS. Taking the 1+2+5 heavy truck as example, the influences of grade, grade length and the entrance speed on the truck speed are analyzed. Then, the functions between the grade and grade length for different speed reduction are set up, which will provide reference for the design of the steep and long longitudinal slope. Considering the fuel economy, the optimum entrance climbing speed is proposed, which will reduce the cost of the transportation and raise the fuel efficiency.Finally, the riding comfort is studied, and the influences of suspension stiffness and absorber damping on the vertical acceleration of body are analyzed. When the shock absorber damping value is decided, not only the suspension stiffness is considered, but also the peak of the body acceleration power spectrum at 2-5Hz and the other smaller peak at 10-20 Hz should be taken into account.