外文翻译---基于无线传感器网络技术的运输网络智能引导及控制系统(编辑修改稿)

外文翻译---基于无线传感器网络技术的运输网络智能引导及控制系统(编辑修改稿)内容摘要：

e information from other units to control the signal light. The main function of roadside unit is to gather the information of the vehicles around, and transfer it to the intersection unit. (Roadside units are installed on the lamp posts along both sides of the road every 50~200m according to the wireless cover range.) The main function of the vehicle unit is to measure the vehicle parameters and transfer them to the roadside units. (Vehicle unit is installed in every vehicle.) The intersection unit, roadside units and vehicle units are denoted as A, B and C in Fig. 2. Roadside units broadcast messages every second. A message includes the ID of the roadside unit and its relative location to the intersection (xB, yB). Normally, vehicle unit is in the listening state. When a vehicle es into the broadcast range of the roadside units and receives the broadcasted message, the vehicle unit switches to the active state. According to the wireless locating method [12。 13], if a vehicle unit receives messages from more than three nodes, it can calculate its location (x, y) and velocity v. After that, the vehicle unit sends the information (x, y, v) to the roadside unit nearby. Based on the (x, y, v) from the vehicles, the roadside unit can calculate the mean speed of the vehicles in its scope. The roadside then transfers the calculated information to the intersection unit. After receiving the messages from the four directions, the intersection unit analyzes the information and makes the decision to control the signal light, or to send navigate information to the vehicle. 3. Optimization Algorithm for Traffic Network Optimization Target From the point view of the whole transportation work, the objective of the proposed ITS is to improve the use efficiency of the work, maximize the mean speed of the whole road work, and reduce the traffic congestions and accidents. From the view of an individual driver or passenger, the objective is to arrive at the destination safely with a minimum cost. The cost may be route length, fuel used, payment for taxi, or time spent. Clearly, the minimum length from the origination to the destination is a static problem, and is out of our discussion. In this paper, we only consider the minimumtraveltime algorithm. That is, the purpose of our optimization algorithm is to minimize the travel time that a vehicle drives from the origination to the destination. Minimum Travel Time Optimization Algorithm The travel time of a vehicle prises the running time on the road and the waiting time for the green light at the intersection. For the ease of discussion, the following a few denotations are defined. Node: The intersection. It is denoted as Ni.(i=0,1,2 „ ) Link: the road from an intersection Ni to a successive intersection Nj. It’ s denoted as Li,j. Link is oneway. Say, Lij≠ L,ij. Total Travel Time (TTT): The total time spent while a vehicle travels from the origination to the destination along a specified route. Link Travel Time (LTT): the time spent while a vehicle travels from a node to the other node along the link. Link Average Velocity (LAV): the average velocity of all the running vehicles in the link. Waiting Greenlight Time (WGT): The time elapsed when a vehicle or a queue waits the righttogo phase in the front of an intersection. The parameter of WGT includes node, ining link, outgoing link, and the time when the vehicle reach the intersection. So it can be denoted as WGT(Node,Lin,Lout,Time). Total Travel Length (TTL): the total route length that a vehicle traveled. The basic idea of the optimization algorithm is that: Before we choose the next link to ride, we firstly predict the time。