Design of road traffic data acquisition system based on ARM9-EEWORLD

Collect

Practical experience at home and abroad has proved that solving urban traffic problems cannot rely solely on building road infrastructure, and intelligent transportation systems (ITS) are the most effective methods and means to solve traffic congestion, reduce traffic accidents, prevent traffic pollution, and improve traffic management. Its characteristic is that information technology enables managers and users to obtain the same information at the same time. Traffic participants can independently choose and implement traffic induction under the condition of known road network operation status, which provides technical support for improving traffic mobility, safety, orderliness, traffic capacity and traffic efficiency of road systems. Therefore, the collection of real-time dynamic information on road traffic has become the most basic link of ITS.

As one of the main means of urban road traffic management, signal control plays an important role in improving urban traffic order, reducing accidents, and improving road utilization. In recent years, urban traffic signal control in my country has developed rapidly. At present, some cities have introduced foreign products, such as SCOOT in the UK, SCATS system in Australia, Quiknet in the United States, Sainco system in Spain, etc., or used domestic research results to establish urban traffic signal control systems for road traffic management. The traffic data information collected by these control devices only serves their own systems and cannot realize the sharing of traffic data information. At present, the collection of traffic data information in most cities in my country relies on the ring coil detectors set under the road surface at the traffic intersection, microwave or radar and video detection equipment on the side of the expressway, etc. Because they were built in different periods and have different development and production backgrounds, they have different types, different information openness, different standards, and different communication transmission and protocols. For example, the measurement and control equipment includes industrial computers, PLCs, single-chip microcomputers or special computers. Existing equipment is unable to cope with the collection, processing and transmission of a large amount of road traffic information including images. In addition, these independent systems and equipment do not cover the entire city. The information between systems and equipment cannot be integrated and shared, and coordination and optimization between systems cannot be achieved. Therefore, the smooth flow and integration of information between them has become the main task of the development of urban traffic signal control systems in my country. The independent systems and signal controllers currently used in many cities have brought considerable difficulties to the smooth flow and integration of system information. Reference [3] uses protocol conversion to achieve its integration and fusion, but it cannot solve the problem of low performance and low processing power of the equipment. Considering the current communication conditions and actual conditions in Chinese cities, this paper designs a road traffic data collection solution that uses an embedded system as a development platform and TCP/IP protocol as a way to transmit traffic information. Due to the development and popularization of the Internet, the use of TCP/IP protocol is simple, convenient, low-cost, open and highly standardized. The nodes on the road communicate data, and the center uses the data collected from each node to control, make decisions and coordinate, and publish information to the outside. The system structure is shown in Figure 1.

2 Data Acquisition System Design[page]

2.1 Basic Requirements

Each node collects, processes and analyzes the information of road traffic flow (mainly motor vehicle flow) (vehicle speed, flow, occupancy rate, emergency alarm, etc.), completes the control of the intersection, and transmits it to the measurement and control center for use by traffic management personnel and reference by drivers. The basic requirements that must be met are as follows:

It is compatible with various types of sensor equipment on the road, that is, it can realize the collection of multi-channel analog and digital signals. The collection time interval is 30 s to 2 min.

It has the function of intersection control and can realize data transmission, processing and control. Once the communication network fails, each node can realize local optimization control through mathematical models based on traffic information, historical data and currently collected information.

The information sent by the measurement and control center is received in real time, and it needs to be released within 5 to 10 minutes so that traffic management personnel and traffic participants can grasp and understand the real-time traffic conditions.

At the same time, it integrates other traffic information, such as public transportation line operation information, emergency-related information, etc. and provides them to road users, making the real-time road information richer.

It has rich communication interfaces (TCP/IP communication interface, 232/USB interface, etc.) and large memory space.

2.2 System Design

2.2.1 Node Hardware Composition

Taking into account the particularity of the outdoor traffic environment, the front-end device adopts an embedded design method, and its hardware composition structure is shown in Figure 2.

As part of the control, the node must complete the control function of the intersection. The control is realized by using the collected traffic data and the coordinated control instructions issued by the center, which are processed by the node. Therefore, a node consists of three functional units: data collection, transmission, and control. The realization of these functions is completed through the embedded system.

According to its functional requirements, its data flow is as follows: first, the data collected from each sensor is processed through the intermediate processing process and displayed in front of the management personnel or on the client terminal for external release; second, the data taken from the information collection system is processed through the intermediate processing process, uploaded to the monitoring center, and stored in the database; third, the monitoring center issues the system coordination control command or the processing result is displayed on the node. The transmission of its data flow is shown in Figure 3.

2.2.2 Data Collection

The main function of traffic data collection is to send the original traffic data such as road traffic flow, speed, occupancy rate, etc. to the node for pre-processing through various traffic detectors. Commonly used ones include ring coil detectors to collect traffic information such as motor vehicle traffic flow and speed; microwave and video detectors can obtain real-time motor vehicle speed, flow, occupancy rate and other traffic flow data; license plate recognition systems can calculate the travel time of motor vehicles on the road; in addition, there are also traffic police on duty on the road who report road conditions and traffic at regular or real-time intervals.

The above-mentioned detectors also have other corresponding functions. For example, the ring coil detector mainly provides real-time traffic data for the signal control system. After the data is processed, it coordinates and controls the traffic lights at the intersection. Video detection is attached to the video surveillance system to provide traffic management personnel with intuitive real-time road images.

In order to ensure the sharing of traffic information, the traffic flow information collected by these detectors must be sent to the node machine for pre-processing to ensure that the collected data is safely, reliably and effectively transmitted to the measurement and control center. [page]

2.2.3 Preprocessing of collected data

The main function of node data preprocessing is to filter the abnormal data collected by various detectors, remove illegal and invalid data, recover fault data, format valid and legal data according to standards, encapsulate it, and send it to the data channel or database designated by the measurement and control center through the communication network using TCP/IP protocol, and provide it to the traffic information processing and analysis subsystem. The real-time detection traffic data obtained after preprocessing is more effective, more in line with the needs of actual conditions, and effectively saves the workload of computer storage.

2.2.4 Control Execution

The system is designed as a distributed client/server network system. On the one hand, the data collected by the node is shared with the upper-level monitoring center. The database collects the image and data information pre-processed by the controller through the optical cable. The control parameters predicted, induced and controlled by the corresponding mathematical model in the monitoring center are used as the control input parameters of the local node. On the other hand, the data of this node is required to be transmitted to the database and the monitoring center. Once the communication system is blocked or fails, the node can also perform local optimal control based on the mathematical model of the local real-time detected traffic flow and historical data. In the event of an accident or other special circumstances, the intersection can also be controlled manually.

2.2.5 Network Communication

The node controller uses the traffic flow information collected by various detectors to control the traffic at the node. At the same time, it must be pre-processed by the processor and transmitted to the control center through the communication interface and TCP/IP protocol to ensure the security, reliability and effectiveness of the collected data for coordinated control and management of the entire traffic system.

3 Implementation Technology

3.1 Hardware Platform

The node processor has to perform heavy communication and algorithm processing, which places high demands on the communication and computing speed of the processor. The performance of traditional single-chip processors is limited and cannot meet the requirements of the node. Therefore, the processor S3C2410 platform of SAMSUNG company is adopted. It has flexible characteristics and powerful performance and has been widely used in embedded systems. The processor integrates a 32-bit microcontroller with ARM920T processor core of ARM company. It has rich resources, with independent 16 kB instruction cache and 16 kB data cache, LCD controller, RAM controller, NAND flash controller, 3-way UART, 4-way DMA, 4-way Timer with PWM, parallel I/O port, 8-way 10-bit ADC, TouchSereen interface, I2C interface, I2S interface, 2 USB interface controllers, 2-way SPI, and the main frequency can reach up to 203 MHz. Based on the rich resources of the processor, relevant configuration and expansion are also carried out. The platform is equipped with 16 MB 16-bit FLASH and 64 MB 32-bit SDRAM. The Ethernet controller chip CS8900A extends a network port and also introduces a HOST USB interface. The hardware platform is shown in Figure 4.

16 MB 16-bit FLASH is used to store the Linux kernel and applications, and 64 MB 32-bit SDRAM is used to store the Linux kernel and applications when the system is running.

The Ethernet controller is used to access the Internet through the Ethernet interface chip CS8900A, and adding a fiber optic interface can realize fiber optic communication.

RS 232 and AD interfaces are used to access LCD controller, traffic light controller, traffic sign controller and detection equipment respectively.

The LCD controller is used to set or modify the control parameters of the intelligent intersection controller, and can also directly control the traffic lights manually.

A camera with a USB port is connected to the USB interface, and the collected video image data is put into the input buffer. Then, it is either saved in the form of a file, or the image processing program transplanted to the platform is run to directly process the buffered image data, and then saved and packaged into a UDP packet. Finally, the image is sent to the Internet through the network interface.

Traffic lights are controlled directly, receiving system parameter settings, such as the number of intersections, traffic light time, etc., and controlling traffic lights. Traffic signs are large screens used to provide traffic information. S3C2410 receives traffic information from the monitoring center and sends this information to the traffic sign controller, which is displayed on the large screen to guide traffic. There are not only a wide variety of detection equipment in current traffic control, but also new products are constantly emerging, and multiple interface methods including serial ports are reserved.

3.2 System Software[page]

The system operating system adopts Linux operating system. Linux kernel is an open source operating system with modular design. Only necessary functional modules are retained, redundant functional modules are deleted, and the kernel is recompiled, so that the hardware resources required for system operation are significantly reduced. The most important point is that Linux has been inseparable from the network since its birth. The Linux system kernel integrates a large number of network applications and supports all standard Internet protocols and almost all networking technologies. This makes Linux very suitable for network-based application development. The program code written by users can be directly built on the basis of these network applications, thereby greatly shortening the development cycle. Therefore, it is applied to the design of intelligent traffic intersection controller, which has the advantages of small code volume, low system resource consumption, high reliability, short development cycle, etc., and meets the requirements of intelligent traffic intersection controller for operating system. The loading process is shown in Figure 5.

3.3 Application Software

The application software mainly includes protocol software, data acquisition module, communication processing module, user interface management, etc. Here we mainly introduce the implementation of video acquisition (included in the data acquisition module) and communication processing.

3.3.1 Video Capture

Using the video device kernel driver video4linux in LINUX, it provides a series of interface functions for programming applications of video devices such as USB cameras, TV cards and video capture cards.

The program writing includes two parts: driver and video stream acquisition application. First, compile the driver module statically, and then use Insmode to dynamically load its driver module program. Then use MMAP() memory mapping method to realize the acquisition of single frame and continuous frame.

3.3.2 Data communication software module

Since TCP/IP protocol is adopted, the communication process adopts C/S mode. The specific flow chart is shown in Figure 6.

4 Conclusion

The embedded data acquisition system proposed in this paper is based on the ARM hardware platform and uses the TCP/IP protocol as the way to transmit traffic information. Through testing and debugging, the above scheme is feasible and can meet the real-time dynamic information collection, control and transmission of traffic. The design has the following characteristics:

(1) The use of the ARM platform can make the system smaller, making it easier to improve performance and connect and expand with various peripherals.

(2) The application of Linux embedded operating system provides a stable and reliable software platform for function expansion, modification and version upgrade.

(3) Traffic data is transmitted through widely available Ethernet resources, making the system truly realize communication transmission without distance restrictions.

The system is compatible with existing equipment and can be used as a single node or as part of an existing node to share traffic data information. It can realize video detection and data return functions, thereby obtaining real-time dynamic information of traffic flow, achieving high integration and sharing of information, and can serve as the basis for processing analysis, data mining and publishing. It can improve the control, management and decision-making level of traffic managers, and also lay a solid foundation for further opening up and building ITS.

Keywords：ARM9 Reference address：Design of road traffic data acquisition system based on ARM9

Previous article：Embedded high-speed image acquisition and storage system based on ARM and FPGA
Next article：ARM pipeline key technology analysis and code optimization

Recommended ReadingLatest update time:2024-11-16 16:47

Design and implementation of 1553B and CAN bus conversion card based on ARM9

1 Introduction The 1553B bus, which was born in the 1970s, is a master-slave multi-redundancy bus with strict regulations on bus hardware, good reliability and real-time performance, and a transmission rate of 1 Mb/s, which can meet the needs of most applications. After decades of development, it has become the

[Microcontroller]

Design and implementation of 1553B and CAN bus conversion card based on ARM9

Software/Hardware Design of Web Server Boa Based on ARM9

1. Introduction to ARM Generally speaking, any dedicated hardware and software system with a microprocessor can be called an embedded system. It is a dedicated computer system embedded in an object system, centered on applications and based on computer technology. The hardware and software can be tailored to meet the

[Power Management]

Software/Hardware Design of Web Server Boa Based on ARM9

Design and application of SD card file system based on ARM9 and μC/OS-II operating system

With the continuous development of embedded technology, ARM processors have been widely used due to their high performance, low cost and low energy consumption. This paper mainly focuses on the demand for access to a large amount of real-time load data in the dynamic weighing system of trucks. Based on the ARM9 em

[Microcontroller]

Design and application of SD card file system based on ARM9 and μC/OS-II operating system

【Technical Support】Building the Qt environment for ARM9 development board

Note: Do not use the QT that comes with the package or installed using apt-get. If there is any, delete it. The development board must be able to mount NFS. This article uses other people's teaching materials, but I have slightly modified them. Because when I first looked for files to do it, I found many mistakes th

[Microcontroller]

Important understanding of ARM9's MMU

MMU seems to me to be a very complicated thing. I read some information on the Internet and barely understood some of the surface things. It has two functions: 1. Map virtual addresses to physical addresses; 2. Provide a control mechanism for memory access. Original address: http://blog.chinaunix.net/u1/58780/showar

[Microcontroller]

Application of embedded system in cable control on 5-meter model of large radio telescope

"FAST (Five hundred meter Aperture Spherical Telescope) Preliminary Research" is a knowledge innovation design program of the Chinese Academy of Sciences . The feed cabin is driven by six suspension cables to achieve large-scale tracking of the feed, ensuring that the positioning accuracy of the feed cabin is within

[Microcontroller]

Application of embedded system in cable control on 5-meter model of large radio telescope

Design and implementation of SD card file system based on ARM9 hardware and software platform

[Microcontroller]

ARM9 big endian mode and little endian mode

(Take ARM9 32-bit storage structure as an example) Little-endian storage mode Straight to the chestnut Data: 0x12345678 (32 bits in total) Address: A+3, A+2, A+1, A (A is the least valid address of this storage area) A+3 = 0x12 A+2 = 0x34 A+1 = 0x56 A = 0x78 Summary: high stores high (high address stores high data);

[Microcontroller]

Popular Resources
Popular amplifiers