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外文翻譯--車輛檢測技術在交通管理上的應用-交通線路.doc

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外文翻譯--車輛檢測技術在交通管理上的應用-交通線路.doc

畢業設計論文外文資料翻譯 院 系 電氣學院 專 業 電氣工程及其自動化 學生姓名 班級學號 外文出處 指導教師評語 指導教師簽名 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. 車輛檢測技術在交通管理上的應用 第1部分 勞倫斯克萊因 顧問 10種不同的檢測技術最近為聯邦公路管理局贊助的智能車輛公路系統節目的一部分而被評估了。這個節目的兩個主要目標是 1. 以確定未來的智能交通系統(ITS)應用的交通參數和相應的測量精度, 2. 為了執行實驗室和現場測試的道路上的安裝,地表和地下檢測器,以確定它們的性能。 所有測試技術的代表性檢測器被發現滿足當前交通管理的要求。但無論怎樣,,提高精度和新的信息類型,如隊列長度和車輛轉彎或不穩定的運動,在未來的交通管理應用中可能需要使用檢測器。一個特定的應用程序的檢測器的選擇,當然,依賴于許多因素,包括所需的數據,精度,監測車道的數量,每通道的檢測區域,檢測器采購和維護成本,供應商的支持,并與當前和未來的交通管理基礎設施的兼容性。 本評估節目的結果被分為兩部分。第1部分介紹了工作原理和各種檢測技術的優勢和弱點。第二部分將提供現場評價數據和一些檢測器的性能和應用的一般性結論。總結報告的副本中,包含了一組5個檢測器的評價數據光盤,其他的皮特米爾斯先生在弗吉尼亞州22101麥克萊恩的6300喬治敦派克的高鐵1號線上寫的報告可從聯邦公路管理局里得到。 注在這篇文章中提出的檢測器性能數據,是克萊因博士他在休斯飛機公司作為該項目的首席研究員時獲得的。 引言 在交通量的不斷增加和有限的建設新的城市,城際,農村的公路設施,最大限度地發揮現有的地面交通網絡的效率和能力是有必要的。街道智能系統,包含流量監控檢測器,實時自適應信號控制系統,駕車通信媒體正在與高速公路和公路的監測和控制系統相結合,以創建智能走廊,增加的交通運輸網絡的有效性。反過來,基礎設施的改善和新技術與通信工具和智能汽車和公共接入領域(如商場)的集成顯示,形成智能交通系統。 車輛檢測器是這些現代化的交通控制系統的基本組成部分。當選擇一個車輛檢測器對交通數據流,以及它們的可靠性,一致性,準確性和精確度,和檢測器響應時間等一些關鍵參數進行評估。隨著檢測器數量的激增,這些屬性變得更加重要和把流量數據的數量和質量,以及對數據的解釋的智能交通系統的實時控制方面,集成到現有的交通控制系統中。 目前的車輛檢測器主要是安裝在地下巷道的感應線圈檢測器(ILDS)。當正確安裝和維護時,它們可以提供實時數據和歷史數據庫作比較可以評估更先進的檢測系統。替代檢測技術正在開發提供一個更廣泛的交通參數,如密度(每公里每車道的車輛),旅行時間,車輛轉向運動等的直接測量。這些先進的檢測器提供更準確的數據,參數不是原來的儀器投入到大面積的監測和控制信號的路口和高速公路直接測量的,以及駕駛者的信息服務的支持。此外,許多先進的檢測系統可以安裝并保持不中斷交通流。一些稀少的地埋檢測器將繼續尋找在未來的應用,例如,在審美方面的問題上主導或程序地方監測和修復故障單元在日常基礎。 目前較新的串行輸出的檢測器需要特定的軟件,要寫入解釋嵌入在數據流中的交通流參數。由于每個檢測器制造商普遍采用了專有的串行協議,每個擁有一個獨特的協議的檢測器需要相應的軟件。這增加了安裝成本或檢測器的實際購買價格。此外,并不是每個檢測器都輸出個別車輛的基礎數據。雖然有些在做,有些在整合從幾十秒鐘到幾分鐘期間該范圍內的數據和輸出結果,生產參數是宏觀交通流的特點。因此,當比較不同的檢測器輸出的時候,交通管理機構必須謹慎使用。 在執行技術評估和分析數據時,重點是放在基于底層技術[1,2]的該檢測器上。這不是確定滿足一系列要求的具體檢測器的用途,而是在于他們是否使用傳感技術測量交通數據并報告流量數據,為現在和未來的應用提供準確的需要。明然,可以有許多實現技術的裝置,其中一些在任何時候可能比另外一些更好地被利用。因此,這種技術可能會在未來的應用中被實現,但當前的硬件或軟件的狀態可能會阻礙其目前的發展。在技術評估過程中實地測試使用的檢測器,在表1中列出。 并非在表格的所有注腳中顯示的所有的檢測器可以使用。表2給出了檢測技術的優點和缺點的一個總結。其中一些有著特定的用途,這意味著一個特定的技術可能適合一些,但并非所有的應用。本表中未涉及的一個因素是檢測器的成本。這個問題也是具體的應用。例如,較高的成本檢測器可能需要具體的數據的應用或多個檢測區域(適用于多車道覆蓋)被歸納入更昂貴的檢測器是適當的。 表3顯示了以上提到的檢測技術在幾個交通管理應用方面的兼容性的例子。假設顯示有關應用的要求,部分的,適當的技術。 以上檢測器的操作理論 以下段落簡要說明了微波,被動紅外,主動紅外,超聲波,被動聲波,視頻圖像處理檢測器的基本工作原理。 微波雷達 在美國使用的微波雷達車輛檢測器發射頻率為10.525 GHz ,由聯邦通訊委員為了此目的而分配頻率。它們的輸出功率由聯邦通訊委員監管和由制造廠商認證,從而符合聯邦通訊委員的要求。沒有進一步的認證要求遵從交通部門它們的部署。 兩種類型的微波雷達檢測器應用在交通管理方面。首先發送在一個恒定頻率的電磁波能量。在其檢測范圍之內,它可以采用發送和接收信號頻率與車速成比例的不同的多普勒原理來測量車輛的速度。因此,檢測到一個頻移就表示一輛車的通行。這種類型的檢測器無法檢測到停止的車輛,因此,不適合應用到需要車輛存在的地方,如在信號燈或停車吧。 第二種類型的微波雷達檢測器發送一個鋸齒波,也稱為調頻連續波(FMCW) ,發射頻率隨時間不斷變化而變化。它允許在檢測器測量車

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