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introduction
In recent years, with the continuous growth of my country’s economy, the number of motor vehicles and the travel rate have increased significantly. The rapid growth, diversification, and time-varying traffic demand is the direct cause of the continuous increase in traffic congestion and the rapid expansion of congested areas . However, limited land resources and other constraints make the construction of road facilities unable to meet the ever-increasing traffic demand. Therefore, higher requirements are put forward for the adaptability and intelligence of traffic signal control. China’s car ownership has exceeded 80 million, and the increase in 2010 alone exceeded 18 million, making it the world’s largest car market. Automobiles are often in motion, and it is difficult to manage them, and as the number continues to increase, the difficulty of managing them increases exponentially. Traditional management methods have become more and more difficult to adapt to changing needs, and new technologies need to be adopted. New means to solve new problems.
1. Application requirements of RFID in vehicle traffic management
1. Supervision requirements for special vehicles. For example, in the management of passenger and freight vehicles, especially the management of muck trucks, due to severely defaced license plates, some low-quality drivers often drive in violation of regulations and even run away in accidents.
2. The requirements of public security management. For example, in the case of a criminal case or a vehicle being stolen with a gun, the relevant personnel and vehicles need to be investigated and tracked in time.
3. Requirements for tolls on roads and bridges. Many roads and bridges are now built with loans. In order to reflect the principle of fairness, whoever uses it pays, so the pay-as-you-go method is adopted. However, when the traffic volume is large, the current parking fee method has a high social cost. There is also the problem of how to identify the driving path of vehicles when the highway network is complex.
4. Solve the requirements of vehicle congestion in the core area of the city. Now all the core areas of big cities have the problem of vehicle congestion. The solution is to use intelligent transportation technology and economic means to adjust the traffic flow.
5. Requirements for access control. For example, the requirements for the management of the entry and exit of resident vehicles and temporary vehicles in a certain unit or community.
6. The requirements of the vehicle management department. For example, vehicles that have not been inspected after the expiry date, vehicles that have not paid compulsory insurance, etc.
7. The requirements of dynamic traffic flow detection in the bus priority RFID intelligent signal light system.
All these requirements ultimately boil down to one requirement: how to adapt to various situations quickly and accurately identify the identity of the monitored vehicle. Currently, the method of video acquisition plus pattern recognition is adopted. However, the quality of the video is greatly affected by the ambient light, especially at night and in rainy and snowy weather, which seriously affects the recognition effect.
Second, the choice of RFID technology
RFID technology is a kind of radio frequency identification technology. The most basic RFID system consists of electronic tags (or tags for short), tag readers (or readers for short) and antennas. Simply put, it uses radio waves to exchange information between the reader and the tag, so as to achieve the purpose of identifying the object attached to the tag.
RFID is divided into active system and passive system in terms of whether the electronic tag has power supply or not; from the working frequency of the radio wave used, it can be divided into low frequency (130KHz), high frequency (13.56MHz), ultra High frequency (900MHz) and microwave (2.4GHz) frequency bands.
The advantages of active RFID are the long recognition distance and the low power of the reader. The disadvantages are high cost, maintenance, and poor directionality for long-distance recognition; the advantages of passive RFID are low cost, maintenance-free, and good directionality for long-distance recognition , The disadvantage is that the distance is short and the power of the reader is large. The higher the frequency of radio waves, the higher the data communication rate, but the more easily the radio waves are blocked (or the worse the diffraction).
Considering many factors, including identification distance, identification direction, comprehensive cost, maintainability, ease of installation, etc., we believe that the choice of UHF passive RFID system for large-scale vehicle management is the most appropriate.
1. Requirements for RFID electronic tags
The foregoing has explained the use of UHF passive RFID systems as a technology for large-scale vehicle management. The following content is aimed at this technology. For labeling, some people have put forward many requirements, but some requirements only consider one aspect without comprehensive consideration of other requirements. After careful research, we finally believe that the following requirements are necessary. It is also more reasonable.
(Electronic label on car glass)
(1) To ensure the uniqueness of the identification number (ID number) in the label, this requires technology and management means to achieve this. Technically, there is a certain threshold to ensure cloning of ID numbers, and management to ensure that cloning is illegal.
(2) It is ensured that the data can be read reliably (reliable recognition) at the highest speed, which is guaranteed by comprehensive processing such as special design and installation.
(3) To ensure the reliable identification of all vehicles under multi-lane, multi-vehicle, and free-flow conditions, it is necessary to comprehensively consider the communication protocol, signal processing, installation plan and other factors to achieve.
(4) After installation, it does not affect driving safety and vehicle performance. It is not easy to be blocked and interfered by people in the car, which affects the reading performance.
(5) From the outside of the car, the color of the label and the installation position are eye-catching, which is easy to cooperate with the video recognition.
(6) The installation is simple and reliable, and the service life is guaranteed for more than 6 years. This life cycle requirement can also be longer.
(7) The installation position is not easy to accumulate water, dust, snow, and is not easy to be damaged.
(8) It can be applied to all types of vehicles as much as possible. Maintenance-free or easy to maintain.
Under the premise of ensuring the above requirements, it is possible to consider the satisfaction of some special application requirements, for example, adding a certain amount of information storage space to meet the reading in a static state.
2. Requirements for RFID readers
VANCH™high performanceRFIDReader
The reader is the key equipment of the RFID system, and it is also the most complex device. The requirements for the use of the RFID reader can be summarized as follows:
(1) The RF power can be adjusted automatically, and the maximum allowable long-term output power should be greater than 36dBm.
(2) There are a variety of sensor interfaces, the purpose is to adapt to the needs of different use environments. (VANCH™ High-Performance RFID Reader)
(3) There is a margin of more than 40% for the reliability of reading and writing tags to resist unknowable environmental interference.
(4) It can meet the requirements for reliable reading of the free flow of the one-way four-lane expressway.
(5) It has data interfaces such as serial port and Ethernet port.
(6) It has the functions of automatic fault diagnosis and service level control, so as to ensure the basic reading function in some cases.
(6) With remote control and software upgrade functions.
(7) Have certain data storage capacity (optional).
(8) It has the reliability requirements for long-term uninterrupted operation.
Other specific performance index requirements are mainly determined according to relevant national standards, and functional requirements can be customized according to actual needs, mainly realized by software.
3. Requirements of RFID antenna
The antenna looks simple, but it is actually very important because it is the carrier of signal transmission and reception, and its performance directly affects the final effect. From the technical indicators, there are mainly gain, half power angle and voltage standing wave ratio, etc., but the flatness (or consistency) of the passband gain and the consistency of the interface impedance are very important, which are often better than those of general mobile communications. Much more demanding.
12dbi RFID antenna
4. Selection of RFID air interface protocol
At present, there are mainly three air interface protocols for 900MHz passive RFID systems in the world, namely ISO-18000-6B, ISO-18000-6C and IPX.
4.1. The ISO-18000-6B protocol came out relatively early. It stipulates that the label has a unique 64-bit (64bits) ID number. The chip is written and cannot be modified when it leaves the factory. The efficiency of reading the ID number is the highest, and the chip can also have user data storage space. , But when reading and writing the content of the user data area, you must first read the ID number of the tag, and then read and write user data to the tag with the specified ID number. Its tag data upload rate is only 40Kbps. The collision arbitration mechanism is a binary tree search algorithm. ,low efficiency.
4.2. The ISO-18000-6C protocol is proposed on the basis of EPC C1G2, and its storage is divided into EPC (product electronic code) area, TID (tag ID area), PASSWORD (password area) and user area (some manufacturers’ The chip does not have this area). Among them, the TID area is written when the chip leaves the factory, and the others are written later. It has the highest efficiency in reading the EPC area. The length of the EPC area is variable from 16 bits to 496 bits, generally 96 bits. When reading and writing other areas The EPC area must be read first. Its tag data upload rate is 40-640Kbps, which is variable. It is determined according to the processing capacity of the reader. The collision arbitration mechanism is the Aloha algorithm, which is more efficient.
4.3. The big difference between the IPX protocol and the above two protocols is that it adopts the TTF (ITF) method, which is called the “label first” method, while the first two protocols are all RTF methods, which is called “reading”. Writer talks first” method. Its advantage is that the reading speed is very fast in the case of a single tag. It has different speed versions, up to 256Kbps, and has a unique 64-bit ID number,
There is also a user area. The anti-collision algorithm uses an improved Aloha algorithm.
In summary, the above three protocols have their own characteristics. The 6C protocol has the best overall performance, but because the EPC code can be written on-site, it is easy to be copied. It is best to customize a private protocol to the chip manufacturer, but this cost is higher.
Lanes with RFID system installed
If it is a large-scale application, it can still be considered. If the 6B protocol is selected, it can meet the various toll requirements for isolation between all access control and lanes, but it is difficult to meet the application of multi-lane free flow; if the 6C protocol is selected, the correlation between other information of the vehicle and the EPC code can be used to ensure Its uniqueness, and in this way, a unified coding specification can be formulated, which is convenient for rapid identification in a wide range of applications. It mainly depends on legislation to solve the problem of illegal copying; if the IPX protocol is selected, its advantage is that it is suitable for the situation where the traffic volume of high-speed sections is not very large. , And the ability of its collision resolution mechanism is difficult to meet the requirements in the case of multi-lane large traffic.
5. Coordination of RFID and video technology
Because the large-scale application of RFID technology to solve vehicle management problems requires a long implementation period, that is to say, there will be vehicles with or without electronic tags for a long time, and it is also for the convenience of manual identification when problems occur. Generally, the place where the RFID system collects vehicle information must be equipped with corresponding video acquisition equipment as a supplement.
3. Composition of vehicle RFID intelligent management system
The system is mainly composed of data acquisition system (RFID reader, antenna, RFID electronic tag), data transmission system (3G network router, wireless HUB, industrial computer, etc.), background management software and database system based on B/S architecture.
Wanquan Intelligent Technology Co., Ltd. is invested and established by Vanch Security Group, an internationally renowned security manufacturing company, and is responsible for the production of Vanch brand products and the sales and after-sales service in the domestic market. Vanch Security Group’s product range covers RFID multi-band radio frequency identification, public safety protection systems, mobile data collection terminals, etc. VANCH brand products are widely used in industries such as transportation, logistics, manufacturing, public and urban all-in-one cards.
Shenzhen Wanquan Intelligent Technology Co., Ltd.
Telephone: 0755-82426775
Fax: 0755-82403457
Website: Http://www.vanch.cn
Address: 2nd Floor, Block B, Taihua Junting, District 45, Baoan District, Shenzhen, Guangdong Province
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