RFID (Radio Frequency Identification) is a non-contact automatic identification technology that automatically recognizes target objects and acquires relevant data through radio frequency signals, and can quickly perform item tracking and data exchange without any manual intervention.
As a new technology, RFID is a combination of radio technology and radar technology. In 1948, Harry Stokeman's "Communication by Reflected Power" laid the theoretical foundation for RFID. The technology was developed in the Second World War. At that time, it was used to identify the aircraft, also known as the "friend or enemy" identification technology, subsequent versions of the technology are still used in aircraft identification.
A typical RFID system consists of three main components: an electronic tag, a reader (including an antenna), and an application system. The electronic tag is a data carrier of the radio frequency identification system. It consists of a tag antenna and a tag-dedicated chip. It can receive the electromagnetic field modulation signal of the reader and return a response signal to realize the reading or writing operation of the tag identification code and the memory data. The reader is used to receive the host-side command and transmit the data stored in the sensor to the host in a wired or wireless manner. The controller and the antenna are included. If the reading distance is long, the antenna will exist separately. The application system refers to the user's original MIS system. The terminal computer of the application system interacting with the RFID system transmits the work instruction issued by the application system, and controls the coordination work between the electronic tag and the reader/writer through the middleware, processes all the data collected by the RFID system, performs calculation and storage and data transmission.
The working principle of the RFID system is to receive the radio frequency signal emitted by the reader when the article with the electronic tag enters the radiation range of the reader antenna. The passive electronic tag transmits the data stored in the tag chip by the energy obtained by the induced current, and the active electronic tag actively transmits the data stored in the tag chip, and the reader is generally equipped with a certain function middleware, which can be read. Take data, decode and directly perform simple data processing, and then send it to the application system. The application system judges the legality of the electronic tag according to the logical operation, and performs corresponding processing and control for different settings, thereby realizing the basic functions of the RFID system.
2. RF tags
The radio frequency tag is a radio frequency card, also known as a non-contact IC card. It consists of an IC chip and an inductive antenna. The chip and antenna are not exposed and are packaged in a standard PVC card. The reading and writing process of the radio frequency card is usually performed by radio waves between the radio frequency card and the reader. It successfully combines radio frequency identification technology and IC card technology, ending the two technical problems of passive and contactless, which is a breakthrough in the field of electronic devices.
According to the power supply method of the tag, the radio frequency tag can be divided into active and passive forms. The active tag uses the energy provided by the power supply inside the tag to identify the distance (up to dozens of meters or even a hundred meters), but the lifespan is limited and the cost is high. The passive tag does not contain a power source. When it is working, it extracts energy from the electromagnetic field of the reader. It is light in weight, small in size, long in life, and low in cost, but the communication distance is limited.
Depending on the operating frequency, RFID systems can be divided into low frequency, medium frequency, ultra high frequency and microwave systems. The operating frequency of the low frequency system is generally between 30KHz and 300KHz, and its typical operating frequency is 125KHz and 133KHz. The basic feature is that the cost of the label is low, the amount of data stored in the label is small, the reading and writing distance is short (about 10 cm), the label has various shapes, and the orientation of the reading antenna is not strong, and is mainly applied to animal husbandry and animal management. The operating frequency of the mid-high frequency system is generally between 3MHz and 30MHz, and its typical operating frequency is 13.56MHz. The basic feature is that the cost of the tag and the reader is relatively low, the amount of data stored in the tag is large, the reading and writing distance is long (more than 1 m), the adaptability is strong, the shape is generally card-shaped, the reader and the tag Antennas have to work properly towards a fixed (range of) direction(s), mainly used in the second generation of PRC ID card system and card system. UHF and microwave systems typically operate at frequencies from 300 MHz to 3 GHz or greater than 3 GHz. Typical operating frequencies are 433MHz, 915MHz, 2.45GHz, and 5.8GHz. According to the characteristics of the radio waves in each frequency band, it can be applied to different occasions. For example, 433MHz active tags are commonly used in the field of short-range communication and industrial control. The choice of 915MHz passive tag logistics. In addition to being widely used in short-range communication, 2.45GHz is also widely used in railway transportation identification management in China. The 5.8GHz RFID system is the working frequency band of China's ETC, and it has taken the lead in formulating the national ETC standard.
ETC (Electronic Toll Collection) is an advanced charging method that is highly respected by all countries in the world. The owner only needs to install an electronic tag on the window. When the vehicle passes through the toll booth, the reader reads and writes the electronic tag passing through the vehicle through the reader set by the toll station, and automatically from the pre-bound RF card or bank account. After deducting the corresponding fees, you can quickly pass through the toll station without stopping and manual payment, and truly realize the smooth flow.
The ETC system is mainly composed of an automatic vehicle identification system, a central management system and other ancillary facilities. The automatic vehicle identification system is composed of an On-board unit (OBU), an RSU (Road side unit), a loop sensor, and the like. The OBU (ie, the electronic tag) stores information about the vehicle and is typically mounted on the front windshield of the vehicle. The RSU (ie, the reader) is installed next to the toll booth. The loop sensor is installed under the driveway floor. The central management system stores a large amount of information about registered vehicles and owners. When the vehicle passes through the toll gate, the loop sensor senses the vehicle, the RSU sends an inquiry signal, the OBU responds, and performs two-way communication and data exchange. The central management system obtains the vehicle identification information, compares and judges, and controls according to different situations. The management system produces different operations to achieve automatic management of the traveling vehicle.
The ETC system is exchanged in a dedicated DSRC (Special Short Range Communication) mode over long distances (10m to 30m), sophisticated encryption communication mechanisms (supporting 3DES, RSA algorithms), and non-contact mode (working frequency bands supporting 915MHz, 2.45GHz, and 5.8GHz). ETC information enables automatic identification of vehicles in fast-moving conditions, enabling automated management of targets.
Compared with the previous manual charging system, the current ETC system has the following advantages: First, the traffic is smoother. The driver can automatically pay through the ETC system without parking, effectively improving the vehicle capacity of the toll booth, avoiding the traffic jam caused by the toll station and improving the road utilization rate. Second, the payment is convenient and transparent. The driver's payment through the ETC system means that the number of vehicles passing through the unit will be more, which will speed up the payment and increase the efficiency of payment. Third, energy saving and environmental protection. The ETC system reduces the waiting time for the vehicle to pay the fee at the toll station, reduces the fuel consumption, and reduces the exhaust emissions when the vehicle is idling, thereby achieving the effect of saving energy and protecting the environment.
The mature application of ETC system has laid a solid foundation for intelligent transportation in the future. Recently, this technology has also been applied to peak congestion charging in urban central areas.
4. Application Fields
Today, the vast majority of access control systems (including garage access and building access) are still being managed using high frequency RF cards. At present, the garage access control system and the building access control system have the following problems during use.
The high-frequency RF card theoretical recognition distance range is only 2.5cm ~ 10cm (the distance between the RF card and the reader). Affected by the environment, the actual recognition distance is shorter than the theoretical recognition distance.
For the garage access control system, the location of the parking gate ticket box requires the driver to drive the vehicle, the main cab position should be close to the parking lot gate box position, in order to swipe the card, thereby increasing the driver's driving. Difficulty, especially the parking lot gate box is set on the side of the garage entrance with a flat slope on one side. Some drivers simply swiped the card, erected the parking brake, and then moved to the garage to drive off the garage. In addition, the parking gate ticket box is generally located at the entrance of the garage, close to the open air environment, and has poor waterproof and moisture-proof performance for thunderstorm weather, thereby increasing the failure rate of electrical originals in the ballot box, resulting in the parking gate not being able to rise and fall normally.
For the building access control system, the distance between the RF card and the card reader should be relatively close, so that the access control can be opened, especially when the personnel enter the building from the outdoor of the thunderstorm weather, and the time for the personnel to wait for the access control through the building is extended. . In view of some problems existing in the current access control system, we draw on the mature application experience of the highway electronic non-stop charging system based on RFID technology, and apply the ETC technology to the current access control system (using the non-stop function module in the ETC system, canceling the ETC system) Charge function module), in order to improve the level of intelligence and efficiency of the access control system, the following solutions are proposed.
(1) Disable the high-frequency RF card currently used in the garage access control system (operating frequency band: 13.56MHz, identification distance range: 2.5cm~10cm), enable microwave radio frequency card (operating frequency band: 5.8GHz, recognition distance range: 10m~30m) . The three sets of antennas of the microwave reader are installed in the "pin" shape on the top and side of the garage entrance and exit wall to fully collect the relevant information of the vehicle's microwave radio frequency card.
(2) Cancel the charging function module in the ETC system, and add video image recognition and voice alarm module. When the vehicle passes through a pre-embedded ground-sensing coil, the vehicle's automatic identification (including radio frequency identification and license plate image recognition) system in the ETC system automatically recognizes the vehicle. If the vehicle is identified as a registered vehicle in the garage, the parking gate is automatically erected and released; if the vehicle is identified as an unregistered vehicle in the garage, the central management system promptly alarms and records the log, reminding the security personnel to arrive in time for processing. .
(3) Deactivate the high-frequency RF card used in the building access control system and enable the microwave RF card in the ETC system. The microwave reader is installed at the entrance of the building to collect information about the microwave RF card. The infrared sense trigger is used to replace the ground sense coil trigger in the ETC system. When a person passes, the infrared sensor triggers the microwave reader to automatically identify the person carrying the microwave RF card. If it is confirmed that the registered personnel information of the building, the building access control will be automatically opened in advance.
(4) For the entry and exit of temporary vehicles and temporary personnel, the temporary microwave radio frequency card can be solved by the administrator.
RFID technology as an emerging automatic identification technology. In particular, microwave radio frequency technology has attracted attention from all walks of life because of its advantages of barrier-free reading and long-distance penetration, fast scanning, high storage capacity, small size, and good security and confidentiality. It stands out from many automatic identification technologies. It is widely used in various fields and has great potential for development in China. Drawing on the mature application experience of the highway electronic toll collection system, the microwave radio frequency technology is used to replace the high-frequency radio frequency technology widely used in the current access control system, and the ETC technology is applied to the above-mentioned access control system to improve the intelligence and efficiency of the access control system. Level of development.
ETC technology has broad application prospects in access control systems, such as the promotion and application of intelligent parking lot management. However, for multiple access control with very close distances within the building, due to the overlapping of the infrared sensing range, multiple microwave readers will be triggered at the same time, which may cause multiple access control personnel to open multiple access control at the same time. Further research and solve it.