Design of Non-stop Toll Collection System Based on RFID Technology


1 Introduction
Non-stop toll collection system is an all-weather intelligent distributed computer control and processing system that can realize non-stop toll collection. It is a comprehensive product of electronic technology, communication and computer, automatic control, sensing technology, traffic engineering and system engineering. The key of non-stop toll collection is to exchange data through radio wave between the vehicle intelligent identification card and the radio transceiver of the automatic toll station vehicle identification system. The type of vehicle and the related data of the user are obtained. The vehicle is controlled and directed by the computer system. The fee is paid automatically from the user's special account in the database through the computer network.
When a vehicle passes through a toll station with an Electronic Toll Collection (ETC), the ETC system automatically completes the whole process of registration, archiving and charging of passing vehicles. Collect, transfer and process all kinds of information of the car without parking. Fig. 1 is a schematic diagram of the non-stop toll collection system.
2 System Hardware Design
In designing the system, the working frequency of radio frequency identification in ETC system should be determined first. The working frequency of 5.8 GHz is the mainstream frequency at present, and it is likely to become the international standard frequency. However, as there is no 5.8 GHz radio frequency module in the domestic market, the radio frequency identification system in this paper is intended to use 915 MHz radio frequency module for experimental research. The overall block diagram of the system is shown in Figure 3.
Its basic working principle: after the electronic tag enters the microwave communication area, the tag reader installed on the roadside transmits the signal through the antenna, and the electronic tag is activated by the radiated signal to enter the working state, and sends the corresponding data back to the reader according to the received command. The m number corresponding to the vehicle will be transmitted to the reader through the electronic tag for the identification of the vehicle by ETC charging system.
2.1 Design of Electronic Label
Because the two-chip electronic tag and dual-interface CPU card are commonly used in the automatic vehicle identification system in our country at present, the reader can also receive some other information. After reading and decoding the information, the reader can send it to the background computer system for data processing. The tag reader will update the information stored in the electronic tag according to the feedback information of the control system. Complete the whole work process.
The ETC radio frequency identification system designed in this paper adopts the active passive read-write type and the dual-chip combination electronic tag with anti-collision function. The electronic label is installed on the dashboard or windshield of the vehicle, and several etc toll channels are set at the toll stations with large traffic flow and easy to cause traffic jams. The driver only needs to insert the dual interface IC card into the dual chip etc electronic label to realize automatic toll collection without stopping, so that the traffic capacity of the toll station can be greatly improved and the traffic pressure can be relieved to the maximum extent. At toll stations with small traffic flow, only IC Card Toll lanes, i.e. manual semi-automatic parking fees, are set up. Drivers should dial out dual-interface IC cards from dual-chip ETC tags to pay by swiping cards on the card switcher, and then pass through the toll station after a short stop.
2.2 Double Redundancy Technology Implementation
Considering that ETC system works in harsh outdoor environment all the year round and will be affected by various weather and pollution, the redundant control of embedded system and single chip computer is adopted to ensure the normal operation of the system in this ETC system.
Embedded system has real-time and stability, powerful functions, and is conducive to product updating. MSP430 is famous for its ultra-low power consumption and super-strong functions. Multiple I/O ports can also provide enough space for future system upgrades. Therefore, this ETC system chooses the dual-core redundancy control of embedded system and MSP430 single-chip computer.
This redundancy design is mainly realized by completing the control systems of ARM system and MSP430. Their control boards can exchange information with RF transceiver chips, collect pulse signals of ground sensor antenna, and control Lane equipment such as railings, sound and light alarms, traffic lights and display screens. 485 communication is used between embedded system and MSP430.
Samsung's ARM9 chip S3C241O is selected for the ARM microprocessor. In order to develop and use the S3C2410 development board for design conveniently, the ARM development board has the following functions: collecting impulse signals from ground sensing coils; SPI interface can exchange information with RF transceiver chips, using 232/485 communication: reserving multiple I/O interfaces to control railings, sound and light alarms, red and green lights, and display. Screen and other lane equipment; with Flash memory.
Design of 3 RF Transceiver
Radio frequency chip is the core of the whole wireless communication unit design. When designing ETC system, we need to consider many realistic factors, including volume, power consumption, transmission rate and so on. Therefore, the choice of RF chip is very important. This system chooses the single chip RF transceiver nRF905 from Nordic Company of Norway.
4. Software Design
The overall software design of ETC electronic toll collection system should include hardware initialization design, OBU wake-up part design, OBU main control unit software, RSU unit function realization software, RSU and lane computer communication interface function realization software design, etc.
The transaction flow design of the software system for vehicles in and out of expressway is shown in Fig. 4.
5 System Testing
The overall function of the electronic toll collection system is tested. The test results are shown in Table 1. The test results show that the overall function test results of the system are satisfactory.