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外文翻译--车辆检测技术在交通管理上的应用-交通线路.doc

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外文翻译--车辆检测技术在交通管理上的应用-交通线路.doc

毕业设计论文外文资料翻译 院 系 电气学院 专 业 电气工程及其自动化 学生姓名 班级学号 外文出处 指导教师评语 指导教师签名 年 月 日 Vehicle Detector Technologies for Traffic Management Applications Part 1 Lawrence A. Klein Consultant Ten different detector technologies were recently evaluated as part of the FHWA-sponsored Detection Technology for IVHS program. The two primary goals of the program were 1. To determine traffic parameters and their corresponding measurement accuracies for future Intelligent Transportation Systems ITS applications, 2. To perform laboratory and field tests with above-the-road mounted, surface, and subsurface detectors to determine their performance. Detectors representative of all tested technologies were found to satisfy current traffic management requirements. However, improved accuracies and new types of information, such as queue length and vehicle turning or erratic movements, may be required from detectors for future traffic management applications. The choice of a detector for a specific application is, of course, dependent on many factors, including data required, accuracy, number of lanes monitored, number of detection zones per lane, detector purchase and maintenance costs, vendor support, and compatibility with the current and future traffic management infrastructure. The results of this evaluation project is being presented in two parts. Part 1 introduces the theory of operation and the strengths and weaknesses of the various overhead detector technologies. Part 2 will provide field evaluation data and some general conclusions about detector performance and applications. Copies of the Final Report, a set of five compact disks containing the detector evaluation data, and other reports are available from the FHWA by writing to Mr. Pete Mills at HSR-1, 6300 Georgetown Pike, McLean, VA 22101. Note The detector performance data presented in this article were obtained by Dr. Klein when he was the project’s Principal Investigator at Hughes Aircraft Company. INTRODUCTION Maximizing the efficiency and capacity of the existing ground transportation network is made necessary by the continued increase in traffic volume and the limited construction of new highway facilities in urban, intercity, and rural areas. Smart street systems that contain traffic monitoring detectors, real-time adaptive signal control systems, and motorist communications media are being combined with freeway and highway surveillance and control systems to create smart corridors that increase the effectiveness of the transportation network. The infrastructure improvements and new technologies are, in turn, being integrated with communications and displays in smart cars and public access areas such as shopping centers to form intelligent transportation systems. Vehicle detectors are an integral part of these modern traffic control systems. The types of traffic flow data, as well as their reliability, consistency, accuracy, and precision, and the detector response time are some of the critical parameters to be evaluated when choosing a vehicle detector. These attributes become even more important as the number of detectors proliferate and the real-time control aspects of ITS put a premium on the quantity and quality of traffic flow data, as well as the ease of data interpretation and integration into the existing traffic control system. Current vehicle detection is based predominantly on inductive loop detectors ILDs installed in the roadway subsurface. When properly installed and maintained, they can provide real-time data and a historical database against which to compare and evaluate more advanced detector systems. Alternative detector technologies being developed provide direct measurement of a wider variety of traffic parameters, such as density vehicles per mile per lane, travel time, and vehicle turning movement. These advanced detectors supply more accurate data, parameters that are not directly measured with previous instruments, inputs to area-wide surveillance and control of signalized intersections and freeways, and support of motorist information services. Furthermore, many of the advanced detector systems can be installed and maintained without disrupting traffic flow. The less obtrusive buried detectors will continue to find applications in the future, as for example, where aesthetic concerns are dominant or procedures are in place to monitor and repair malfunctioning units on a daily basis. Newer detectors with serial outputs currently require specific software to be written to interpret the traffic flow parameters embedded in the data stream. Since each detector manufacturer generally uses a proprietary serial protocol, each detector with a unique protocol requires corresponding software. This increases the installation cost or the real purchase price of the detector. Furthermore, not every detector outputs data on an individual vehicle basis. While some do, others integrate the data and output the results over periods that range from tens of seconds to minutes, producing parameters that are characteristic of macroscopic traffic flow. The traffic management agency must thus use caution when comparing outputs from dissimilar detectors. In performing the technology evaluations and in analyzing the data, focus was placed on the underlying technology upon which the detectors were based [1,2]. It was not the purpose of the program to determine which specific detectors met a set of requirements, but rather whether the sensing technology they used had merit in measuring and reporting traffic data to the accuracy needed for present and future applications. Obviously, there can be many implementations of a technology, some of which may be better exploited than others at any time. Thus, a technology may show promise for future applications, but the state-of-the-art of current hardware or software may be hampering its present deployment. The detectors that were used in the technology evaluations during the field tests are listed in Table 1. Not all detectors were available at all sites as shown in the footnotes to the table. A summary of the advantages and disadvantages of the detector technologies is given in Table 2. Some of them are application specific, implying that a particular technology may be suitable for some but not all applications. A factor not addressed in this table is detector cost. This issue is again application specific. For example, a higher cost detector may be appropriate for an application requiring specific data or multiple detection zones suitable for multiple lane coverage that are incorporated into the more expensive detector. Table 3 shows examples of overhead detector technology compatibility with several traffic management applications. The assumptions shown concerning the application dictate, in part, the appropriateness of the technology. THEORY OF OVERHEAD DETECTOR OPERATION The following paragraphs give a brief explanation of the underlying operating principles for microwave, passive infrared, active infrared, ultrasonic, passive acoustic, and video image processor detectors. Microwave Radar Microwave radars used in the U.S. for vehicle detection transmit energy at 10.525 GHz, a frequency allocated by the FCC for this purpose. Their output power is regulated by the FCC and certified by the manufacturer to meet FCC requirements. No further certification is required of the transportation agencies for their deployment. Two types of microwave radar detectors are used in traffic management applications. The first transmits electromagnetic energy at a constant frequency. It measures the speed of vehicles within its field of view using the Doppler principle, where the difference in frequency between the transmitted and received signals is proportional to the vehicle speed. Thus, the detection of a frequency shift denotes the passage of a vehicle. This type of detector cannot detect stopped vehicles and is, therefore, not suitable for applications that require vehicle presence such as at a signal light or stop bar. The second type of microwave radar detector transmits a sawtooth waveform, also called a frequency-modulated continuous wave FMCW, that varies the transmitted frequency continuously with time. It permits stationary vehicles to be detected by measuring the range from the detector to the vehicle and also calculates vehicle speed by measuring the time it takes for the vehicle to travel between two internal markers range bins that represent known distances from the radar. Vehicle speed is then simply calculated as the distance between the two range bins divided by the time it takes the vehicle to travel that distance. Since this detector can sense stopped vehicles, it is sometimes referred to as a true-presence microwave radar. Passive Infrared Detectors Passive infrared detectors can supply vehicle passage and presence data, but not speed. They use an energy sensitive photon detector located at the optical focal plane to measure the infrared energy emitted by objects in the detector’s field of view. Passive detectors do not transmit energy of their own. When a vehicle enters the detection zone, it produces a change in the energy normally measured from the road surface in the absence of a vehicle. The change in energy is proportional to the absolute temperature of the vehicle and the emissivity of the vehicle’s metal surface emissivity is equal to the ratio of the energy actually emitted by a material to the energy emitted by a perfect radiator of energy at the same temperature. The difference in energy that reaches the detector is reduced when there is water vapor, rain, snow, or fog in the atmosphere. For the approximately 20 ft 6.1 m distances typical of traffic monitoring applications with this type of detector, these atmospheric constituents may not produce significant performance degradation. Active Infrared Detectors Active infrared detectors function similarly to microwave radar detectors. The most prevalent types use a laser diode to transmit energy in the near infrared spectrum approximately 0.9 micrometer wavelength, a portion of which is reflected back into the receiver of the detector from a vehicle in its field of view. Laser radars can supply vehicle passage, presence, and speed information. Speed is measured by noting the time it takes a vehicle to cross two infrared beams that are scanned across the road surface a known distance apart. Some laser radar models also have the ability to classify vehicles by measuring and identifying their profiles. Other types of active infrared detectors use light emitting diodes LEDs as the signal source. Ultrasonic Detectors Ultrasonic vehicle detectors can be designed to receive range and Doppler speed data. However, the most prevalent and low-cost ultrasonic detectors are those that measure range to provide vehicle passage and presence data only. The ultrasonic Doppler detector that also measures vehicle speed is an order of magnitude more expensive than the presence detector. Ultrasonic detectors transmit sound at 25 kHz to 50 kHz depending on the manufacturer. These frequencies lie above the audible region. A portion of the transmitted energy is reflected from the road or vehicle surface into the receiver portion of the instrument and is processed to give vehicle passage and presence. A typical ultrasonic presence detector transmits ultrasonic energy in the form of pulses. The measurement of the round-trip time it takes for the pulse to leave the detector, bounce off a surface, and return to the detector is proportional to the range from the detector to the surface. A detection gate is set to identify the range to the road surface and inhibit a detection signal from the road itself. When a vehicle enters the field of view, the range from the detector to the top of the vehicle is sensed, and being less than the range from the detector to the road, causes the detector to produce a vehicle detection signal. Passive Acoustic Detectors Vehicular traffic produces acoustic energy or audible sound from a variety of sources within the vehicle and from the interaction of the vehicle’s tires with the road surface. Arrays of acoustic microphones are used to pickup these sounds from a focused area within a lane on a roadway. When a vehicle passes through the detection zone, the signal-processing algorithm detects an increase in sound energy and a vehicle presence signal is generated. When the vehicle leaves the detection zone, the sound energy decreases below the detection threshold and the vehicle presence signal is terminated. 车辆检测技术在交通管理上的应用 第1部分 劳伦斯克莱因 顾问 10种不同的检测技术最近为联邦公路管理局赞助的智能车辆公路系统节目的一部分而被评估了。这个节目的两个主要目标是 1. 以?#33539;?#26410;来的智能交通系?#24120;↖TS)应用的交通?#38382;?#21644;相应的测量精度, 2. 为了执行实验室和现场测试的道路上的安装,地表和地下检测器,以?#33539;?#23427;们的性能。 所有测试技术的代表性检测器?#29615;?#29616;满足当前交通管理的要求。但无论怎样,,提高精度和新的信息类型,如队列长度和车辆转弯或不稳定的运动,在未来的交通管理应用中可能需要使用检测器。一个特定的应用程序的检测器的选择,当然,?#35272;?#20110;许多因素,包括所需的数据,精度,监测车道的数量,每通道的检测区域,检测器采购和维护成本,供应商的支持,并与当前和未来的交通管理基础设施的兼容性。 本评估节目的结果被分为两部分。第1部分介绍了工作原理?#36879;?#31181;检测技术的优势和弱点。第二部分将提供现场评价数据和一些检测器的性能和应用的一般性结论。总结报告的副本中,包含了一组5个检测器的评价数据光盘,其他的皮特米尔斯先生在弗吉尼?#20405;?2101麦克莱恩的6300?#20405;?#25958;派克的高铁1号线上写的报告可从联邦公路管理局里得到。 注在这篇文章中提出的检测器性能数据,是克莱因博士他在休斯飞机公司作为该项目的首席研究员?#34987;?#24471;的。 引言 在交通量的?#27426;?#22686;加和有限的建设新的城市,城际,农村的公路设施,最大限度地发挥现有的地面交通网络的效率和能力是有必要的。街?#20048;?#33021;系?#24120;?#21253;含流?#32771;?#25511;检测器,实时自适应信号控制系?#24120;?#39550;车通信?#25945;?#27491;在与高速公路和公路的监测和控制系统相结合,?#28304;?#24314;智能走廊,增加的交通运输网络的有效性。反过来,基础设施的改善和新技术与通信工具和智能汽车和公共接入领域(如商场)的集?#19978;?#31034;,形成智能交通系?#22330;?车辆检测器是这些现代化的交通控制系?#36710;?#22522;本组成部分。当选择一个车辆检测器对交通数据流,以及它们的可靠性,一致性,?#26082;沸院?#31934;确度,和检测器响应时间等一些关键?#38382;?#36827;行评估。随着检测器数量的激增,这些属?#21592;?#24471;更加重要和把流量数据的数量和质量,以及对数据的解释的智能交通系?#36710;?#23454;时控制方面,集成到现有的交通控制系?#25345;小?目前的车辆检测器主要是安装在地下巷道的感应线圈检测器(ILDS)。当正确安装和维护?#20445;?#23427;们可以提供实时数据和历史数据库作比较可以评估更先进的检测系?#22330;?#26367;代检测技术正在开发提供一个更广泛的交通?#38382;?#22914;密度(每公里每车道的车辆),旅行时间,车辆转向运动等的直接测量。这些先进的检测器提供更?#26082;?#30340;数据,?#38382;?#19981;是原来的仪器投入到大面积的监测和控制信号的路口?#36879;?#36895;公路直接测量的,以及驾驶者的信息服务的支持。此外,许多先进的检测系统可以安?#23433;?#20445;持不中断交通流。一些稀少的地埋检测器将继续寻找在未来的应用,例如,在审美方面的问题上主导或程序地方监测和修复故?#31995;?#20803;在日常基础。 目前?#38386;?#30340;串行输出的检测器需要特定的软件,要写入解释嵌入在数据流中的交通流?#38382;?#30001;于每个检测器制造商普遍采用了专有的串行协议,每个拥有一个独特的协议的检测器需要相应的软件。这增加了安装成本或检测器的?#23548;使?#20080;价格。此外,并不是每个检测器都输出个别车辆的基础数据。虽然有些在做,有些在整合从几十秒钟到几分钟期间该范围内的数据和输出结果,生产?#38382;?#26159;宏观交通流的特点。因此,当比较不同的检测器输出的时候,交通管理机构必须谨慎使用。 在执行技术评估和分析数据?#20445;?#37325;点是放在基于底层技术[1,2]的该检测器上。这不是?#33539;?#28385;足一系列要求的具体检测器的用途,而是在于他们是否使用传感技术测量交通数据并报告流量数据,为现在和未来的应用提供?#26082;?#30340;需要。明然,可以有许多实现技术的装置,其中一些在任?#38382;?#20505;可能比另外一些更好地被利用。因此,这种技术可能会在未来的应用中被实现,但当前的硬件或软件的状态可能会阻碍其目前的发展。在技术评估过程中实地测试使用的检测器,在表1中列出。 并非在表格的所有注脚中显示的所有的检测器可以使用。表2给出了检测技术的优点和缺点的一个总结。其中一些有着特定的用途,这意味着一个特定的技术可能适合一些,但并非所有的应用。本表中未涉及的一个因素是检测器的成本。这个问题也是具体的应用。例如,较高的成本检测器可能需要具体的数据的应用或多个检测区域(适用于多车道覆盖)被归纳入更昂贵的检测器是?#23454;?#30340;。 表3显示了以上提到的检测技术在几个交通管理应用方面的兼容性的例?#21360;?#20551;设显示有关应用的要求,部分的,?#23454;?#30340;技术。 以上检测器的操作理论 以下段落简要说明了微波,被动红外,主动红外,超声波,被动声波,视频图像处理检测器的基本工作原理。 微波雷达 在美国使用的微波雷达车辆检测器发射频率为10.525 GHz ,由联邦通讯委员为了此目的而分配频率。它们的输出功率由联邦通讯委员监管和由制造厂商认证,从而符合联邦通讯委员的要求。没有进一步的认证要求遵从交通部门它们的部署。 两种类型的微波雷达检测器应用在交通管理方面。首?#30830;?#36865;在一个恒定频率的电磁波能量。在其检测范围之内,它可以采用发送和?#37038;?#20449;号频率与车速成比例的不同的多普勒原理来测量车辆的速度。因此,检测到一个频移就表示一辆车的通?#23567;?#36825;种类型的检测器无法检测到停止的车辆,因此,不适合应用到需要车辆存在的地方,如在信号灯或停车吧。 第二种类型的微波雷达检测器发送一个锯齿波,也称为调频连续波(FMCW) ,发射频率随时间?#27426;?#21464;化而变化。它允许在检测器测量车

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