外文翻譯---基于無(wú)線傳感器網(wǎng)絡(luò)技術(shù)的運(yùn)輸網(wǎng)絡(luò)智能引導(dǎo)及控制系統(tǒng)(文件)
【正文】 ontrol 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 cost of the candidate routes. The route with the minimum cost is then chosen as the best route. In order to predict the total time cost, we should know the travel time in all links to pass and the waiting time before every intersection. Let’ s see a simple situation. As shown in , the current time is τ 。 2) some are measured by the surveillance subsystem, such as the mean speed, the number of the vehicles on a link。 in [6], Di Febbraro presents a hybrid Petri Net module to address the problem of intersection signal lights coordination. The control subsystem controls the signal lights on the intersection. The guiding subsystem provides the realtime traffic information for the drivers to select the best route. The navigation subsystem uses satellite signal such as GPS to locate the specific vehicle, and with the help of electronic map, select the optimal route for the vehicle. One shortage of the systems mentioned above is that the sensors can only detect the vehicles in a fixed spot. They can not track the vehicles out of the spot. Clearly, if we can monitor and measure the traffic status dynamically in real time, an efficient traffic control will be easier to realize. With the development of microelectronic and puter technologies, the lowpowerconsumption, lowcost and relatively powerful wireless sensor work (WSN) technology has been applied in many areas[79]. However, the application of WSN in the traffic control system is rarely documented. In [10], we proposed a WSNbased system
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