Research On The Driving Characteristics Of Tractor-semitrailer Vehicle In Longitudinal Slope Of Mountainous Expressway

With the rapid growth of the national economy,the gradual development of the material circulation industry,freight volume is increasing,highway freight amount accounted for more than 75% percent of the total freight.Due to its large volume and the characteristics of high economic efficiency,Tractor-semitrailer vehicle bear the main transport tasks,the number will continue to increase,on the freeway in the vehicle,the proportion of half-hung car trains has increased in the vehicle on the freeway.Meanwhile,the related traffic accidents gradually increased.The existing traffic accident investigation shows that the outline size of Tractor-semitrailer vehicle is large,the power of tractor is small,the mountainous expressway ramp up and the large slope occupy ratio,the vehicle braking is weak and so on are the main causes of the traffic accidents.There are more researches on the braking safety of the vehicle and its braking performance.This paper focuses on the running process of the Tractor-semitrailer vehicle in the mountainous Expressway slope section,and studies its influence on safe driving.In this paper,using the method of road test and simulation,select Representative Dongfeng Tianlong Tractor-semitrailer vehicle in Chongqing area G42 Expressway Liangping-Wanzhou section to do the road experiment,in the Fengjie-Wuxi expressway downhill driving test.At the same time,using the TruckSim software,the whole vehicle simulation driving system consisting of Tractor-semitrailer vehicle model,road model and driver model is established.The factors such as the speed V,vehicle power,load M,longitudinal slope value i,bend radius R,Bend corner f,bend transverse slope ih,Location of Load centroid,the impact of the car train operation parameters.Research shows: The average longitudinal acceleration a and the initial velocity v of the vehicle in the uphill(i>0)driving process showed a significant linear negative correlation.When the road longitudinal slope i?4%,the vehicle climbing the initial speed V?60km/h,due to the inertia force function,the vehicle's stable climbing distance S with the increase of the truck,the slope,the speed is higher,S with the increase of load and decrease.The number of the driver's shift K is linearly positive correlation with the ramp velocity v and slope i.The power ratio of the vehicle per increase 0.01 k W/kg,the vehicle's lowest driving speed increase Vmin is approaching 10km/h,increasing the vehicle's ratio power can effectively improve the speed of the vehicle climbing.In the course of the downhill(i<0)turning,the smaller the slope of the road,the more obvious the impact of the vehicle speed on the lateral acceleration of the bend.The lateral acceleration of the vehicle at the downhill corners increases with the increase of corners of the bend in the process of changing corners from 0° to 7.5°.In the vehicle 35 t,through the bend radius 450 m bend,the load centroid distance from the front axle D1,the load centroid distance from the ground D2 respectively less than 7000 mm,2300mm when the vehicle can safely drive across the bend.The above results provide a basis for limiting speed,limiting load,preventing rear-end collision and lifting the ratio power of Tractor-semitrailer vehicle on typical slopes of mountainous highway.