Study On The Optimization Of Truck Platoon Formation Considering Infrastructure Durability And Energy Consumption

As one of the commercial applications of autonomous driving technology,autonomous truck platoon can be firstly applied to closed traffic scenes such as the expressway and port terminals because of its advantages in reducing drivers’ working load and vehicles’ fuel consumption.In order to maximize the fuel savings,the truck platoon looks like a train and runs along the center of the lane.While pursuing the benefits of truck platoon,it must be realized that the truck platoon running along the center of the lane will cause channelized vehicle loads.This will result in repeated loads and damage in some parts of the pavement,but other parts will not be fully utilized.Channelized vehicle loads will accelerate the pavement damage and cause economic losses,while discrete platoon will get fewer fuel savings.How to balance the fuel savings and the road economic losses caused by truck platoon,and propose some solutions are the urgent issues to be solved before the application of truck platoon.To this end,this study carried out the following work:1)Feature extraction and scheme design of autonomous truck platoon: the current technology lacks consideration of the morphological characteristics of autonomous truck platoon.It is necessary to figure out the parameters such as the lateral distribution state,lateral distribution area and longitudinal interval of truck platoon.The traffic flow video of Shanghai-Hangzhou-Ningbo Expressway was collected,and the distribution data of human-driven vehicles in the cross section of the lane were extracted.Through the fitting of probability density function,the lateral distribution states and lateral distribution area of various types of human-driven vehicles were determined.Based on the characteristics of human-driven vehicles,the current situation and prospect of automatic driving technology,six lateral distribution widths,two lateral distribution modes,seven longitudinal intervals and three formation forms of truck platoon were proposed.The rolling times of the lane under each scheme were preliminarily analyzed,and the formation schemes that should be considered in the subsequent chapters were determined.2)Building of fuel consumption prediction model and database of platoon’s air drag coefficients under random parameters: the fuel consumption of truck platoon is closely related to its formation parameters.This study analyzed the force of vehicles from the perspectives of rolling resistance,air drag,slope resistance and inertia resistance,and found that air drag played an important role in vehicle fuel consumption.The vehicle fuel consumption model under the influence of multiple factors was built,and model parameters were determined through the vehicle engine’s experimental data.The models of 2745 platoons under each working condition were built,and the air drag coefficient of each platoon was solved.The head vehicle of a two-truck platoon is weakly affected by the lateral offset,and its air drag coefficient is 87.43%-100.6% of that of a single vehicle;The rear vehicle is obviously affected by the longitudinal intervals and lateral offset,and its air drag coefficient is 58.00%-76.30% of that of a single vehicle.Influenced by the lateral offset and longitudinal interval,the air drag coefficient of the first vehicle of a three-truck platoon is 84.19%-100.9% of that of a single vehicle;the second vehicle’s air drag coefficient is 45.65%-81.19% of that of a single vehicle,and the tail vehicle’s air resistance coefficient is 45.24%-77.20% of that of a single vehicle.3)Rutting development and fatigue damage accumulation of the asphalt pavement under random platoon parameters: Formation of a truck platoon not only affects fuel consumption,but also directly affects the vehicle loads.In order to clarify the key nodes of pavement’s state,it is necessary to figure out the law of pavement performance influenced by factors like temperature and truck platoon parameters.Firstly,this study collected the annual atmospheric temperature,material parameters,sunshine data,wind speed and other data.The temperature fields of asphalt pavement structure were analyzed,which formed 288 data curves.Based on the typical asphalt pavement structure of Shanghai-Hangzhou-Ningbo Expressway,the influence of platoon parameters on the development of pavement rutting was analyzed,so as to figure out the law of pavement rutting development under continuous variable temperature conditions,different lateral distribution states and distribution widths.Based on the Miner’s Law and empirical formula,a fatigue damage accumulation model of asphalt layer considering the platoon strategy was constructed.The strain distribution at the bottom of asphalt layer under standard axle load was analyzed with the finite element model,and the fatigue damage accumulation rates of asphalt layer under different platoon strategies were quantitatively compared.4)Evaluation of fuel savings and maintenance cost loss of different platoon schemes: the platoon scheme in this study throws a certain impact on fuel consumption and pavement performance.It is necessary to quantify the impact of the two parts from the perspective of economic cost and get a balance point.Firstly,the fuel consumption distributions of different platoon strategies were calculated by Monte Carlo simulation,and the fuel saving benefits under different platoon strategies were estimated.On the whole,three-truck platoon behaves better than two-truck platoon and single vehicle.The smaller the longitudinal interval is,the higher the fuel saving rate will be.The individual discrete formation strategy almost eliminates the adverse impact caused by lateral offset.According to the estimation results under the traffic volume of 1.757 million standard axle load per lane of Shanghai Hangzhou Ningbo Expressway every year,when the freight vehicles are organized in three vehicle formation,the annual fuel saving benefit of each lane per kilometer is 163,600 yuan to 327,700 yuan(with a longitudinal interval from 48 m to 6m).In terms of pavement maintenance,the current driving platoon will shorten the pavement maintenance cycle.Within a surface maintenance cycle,the annual maintenance cost will rise from 175,000 yuan per lane per kilometer to 572,000 yuan per lane per kilometer,and the fuel savings can not make up for the maintenance loss.Considering both the fuel saving and maintenance cost investment,this study puts forward a short-term scheme and a long-term scheme of the truck platoon,which can realize the comprehensive economic benefits of 185,000 yuan and 339,000 yuan per lane per kilometer per year respectively.The long-term scheme will still be able to obtain the fuel savings of the current platoon while saving some pavement maintenance costs.This study is an exploratory study on the autonomous truck platoon,which promotes the interdisciplinary application of transportation engineering.This study provides a certain reference for the practical application of truck formation technology and road owners,and can avoid the development of truck formation technology falling into local optimization.