In order to accurately and timely discover the fault of the railway contact network compensation device, the paper checks whether the contact network compensation device is stuck or not by monitoring the ambient temperature of the contact network and the change of the length of the bearing cable and the contact line. The system uses the C8051F930 chip as the main controller of the system, and uses the SIM900A wireless transmission module as the wireless controller. The communication node of the network sends data to the server at different time intervals, and connects the node to the remote server in combination with GPRS wireless communication technology and Web Internet technology. The experimental results show that the system has stable performance and high detection accuracy, which meets relevant design requirements.
Contact network; compensation device; remote monitoring system; GPRS; SIM900A
TN806 document identification code: ADIO: 10.19358/j. Issn. 1674-7720.2017.05.002
Reference format: Tan Pengliu, Zhou Le, Mao Sumin. Design of remote monitoring system for contact network compensation device based on GPRS [J]. Microcomputers and Applications, 2017, 36(5): 4-7, 10.
0 Preface
Fund Project: National Natural Science Foundation of China (61364023); Aviation Funded Project (2013ZD56008); Jiangxi Provincial Department of Education Science and Technology Project (GJJ13516) With the increase of train speed, the railway operation density is gradually increased, and the traction power supply system is safe. The requirements for reliability are also getting higher and higher. The contact net is one of the important equipments of the traction power supply system [1~4]. The contact network in operation must withstand the high-speed contact friction operation of the electric locomotive with a certain pressure, and the current through the contact net is up to 1 000 A or more. The net is also affected by tension, arc, snow, fog and air pollution, so that the contact network is constantly in the dynamic state of vibration, friction, arc, pollution, and telescopicity. Once a fault occurs, the traffic will be interrupted. Disrupting the transportation order of electrified railways and causing economic losses [5]. Quickly and accurately discovering faults, promptly and promptly repairing, eliminating power supply accidents, and minimizing the impact of accidents are the goals pursued by the railway electrification section operation and maintenance industry, and are efforts to improve the quality of railway services. Online monitoring of the contact network is one of the important methods to improve the reliability of the contact network. This paper studies the online monitoring technology of the contact network and proposes a remote monitoring system design of the contact network compensation device based on GPRS.
1, the overall design of the system
As the atmospheric temperature changes, the load-bearing cable and the contact line will linearly elongate (or shorten). By monitoring the temperature and humidity of the environment in which the contact net is located and compensating for the displacement between the falling anchor and the anchor post under the contact net, the temperature is compared. The displacement change underneath determines whether the contact network has a compensation stuck phenomenon and realizes the monitoring of the contact network. The remote monitoring system of the contact network compensation device is installed between the bracket and the falling device. When measuring, the device has little influence on the operating state of the contact net.
Figure 1 System overall block diagram GPRS-based contact network compensation device remote monitoring system architecture shown in Figure 1, the dotted line in the figure indicates that the signal is transmitted wirelessly. The system is composed of a wireless collection node, a GPRS base station, an internet server, and a user terminal (computer). The working process of the system is to periodically collect data for the temperature and humidity sensor and the displacement sensor, and use the SIM900A module to send the collected data to the Internet server through the base station, and the computer user completes the temperature and displacement monitoring through the Internet.
The system has the following advantages: (1) The power supply and monitoring module not only can provide stable DC voltage, but also can quickly detect the voltage and on-off of the power supply to ensure that the saved data is not lost; (2) Adopt [6] The card carries out GPRS wireless data transmission to ensure the data transmission rate and reliability, and the used fee is lower than the GSM short message tariff.
2, system hardware design
The system hardware mainly includes power module, microprocessor module, GPRS communication module, sensor, etc. The system hardware composition is shown in Figure 2.
2.1 power module
The power system input voltage is AC 220 V, the output 12 V is the op amp power supply, 5 V is the external sensor power supply, 4 V is the GPRS module power supply, and 3.3 V is the MCU module power supply, as shown in Figure 3. Stable power supply is the basis for the system to work safely and efficiently. Considering the harsh environment of the contact network, the power input terminal uses the Jinshengyang LD10-2020 power conversion module [7] to convert the 220 V AC input to +12 V/1. A
Output. LD10-202012 is a small-volume switching power supply module with output short-circuit, over-current, over-voltage protection and other functions. Its EMC and safety specifications meet the international IEC/EN61000-4, CISPR11/EN55011, UL60950, and EN60601 standards. The most important is that the power module output isolation voltage up to 4 000 V AC, suitable for high isolation and strict electromagnetic compatibility applications.
2.2 Micro Processing Template
The wireless collection node is the core component of the system. Considering the application and function characteristics of the system, it must meet the requirements of high performance, low power consumption, low cost and small volume, and is easy to install and maintain. In the hardware design, the C8051f 930 MCU is selected as the microprocessor [8], which is compatible with the 8051 core. The extended interrupt system provides multiple interrupt sources for the CIP-51.
Data acquisition, power module control, power failure monitoring, etc. The MCU communicates with the GPRS through the serial port, communicates with the temperature sensor through the I2C interface simulated by the IO port, and collects the analog voltage signal output by the pull-line displacement sensor through the IO port.
2.3GPRS communication module
Wireless communication methods include infrared, Bluetooth, WiFi, ZigBee, GPRS, etc., but in the data transmission distance of more than 1 km, the most reliable, convenient and lowest cost way is GPRS. GPRS wireless network has the characteristics of wide coverage, fast access speed, low cost of use and always online [9  10], so the host computer monitoring system can obtain relevant parameters of the contact network compensation device in time, and analyze whether the contact network compensation device is in real time. Reliable operation. The GPRS module uses Simcom's SIM900A module, which integrates various network communication protocols, which can realize the remote transmission of voice, SMS, data and other information, and can realize the connection with the GPRS network through AT commands.
The GPRS module circuit is shown in Figure 4. It consists of an antenna, an impedance matching circuit, a SIM card circuit, and an ESD protection circuit. The RF pin is connected to a 50 Ω RF antenna, and the TXD and RXD pins are respectively connected to the MCU serial port receiving end and the transmitting end. The SIM card used in the system is a 13-digit IoT card, and users can obtain rich code number resources. And the Internet of Things has high-quality network performance. By building IoT SMS Center, Internet of Things GGSN, Internet of Things (HLR) and other IoT-specific network elements, the network separation between IoT users and mass users is realized, providing reliable and stable solutions for industry customers. The internet. The user can manage the working status and communication status of the terminal in real time through the interface provided by the application platform.
2.4 lightning protection interface design
Electronic systems may be subject to transient over-voltage disturbances, including: overvoltages caused by switching inductive loads or starting and stopping high-power loads, line faults, etc., lightning surges caused by natural phenomena such as lightning [11]. In order to avoid the surge voltage damage to the electronic equipment, the clamp protector is adopted in the design, that is, after the breakdown of the protection device, the voltage across the two ends of the protection device does not rise, and the protection function is mainly clamped. The device is a zinc oxide varistor (MOV), transient voltage suppressor (TVS).
3, system software design
3.1 lower computer program design
The lower computer software is written in C language and compiled under the Keil 4 C51 compiler. The software design of the lower computer system mainly includes two parts: one is the control of the power module and the data acquisition by the single chip; the other is the data transmission of the GPRS module. The lower computer software function module is composed as shown in Figure 5.
3.2 MCU control of power module and data acquisition
In order to reduce power consumption, the MCU collects a set of data and then sleeps for a period of time before data acquisition. The MCU has two working states, namely, data acquisition state and sleep state. In the data acquisition state, the power switch is turned on through GPIO26 to supply power to the peripheral modules, and GPRS communication initialization, data acquisition, and data transmission are performed. In the sleep state, the power switch is turned off by the GPIO26, and the peripheral module is powered off while the MCU is operating in the sleep mode.
3.3GPRS module data transmission
The MCU exchanges data with the GPRS module through the serial port, including serial port initialization, writing serial port data and other functions. Reading serial data is done by interrupt. Write the driver function of the GPRS module based on the serial port function. The control method is to use the AT command [12]. The main commands involved are shown in Table 1.
The GPRS terminal and the data center communicate with each other according to their respective IP addresses. There are three kinds of commonly used system networking methods [13-14]: (1) Using public network fixed IP, fast communication speed, reliable operation, simple networking, but this method must have a fixed IP address, and the overall cost is high. (2) Adopting the dynamic IP+DNS domain name resolution method of the public network, the communication speed is moderate, the communication quality is relatively stable, the network construction workload is small, and the communication cost is low. (3) The GPRS dedicated line method has good data security and fast communication speed, but the initial construction cost of the system is high. Considering the conditions of the system experiment, the system adopts the networking mode of dynamic IP+DNS domain name resolution on the public network.
3.4 PC programming
During data collection, the node automatically performs an acquisition task every 30 minutes and sends the collected data to the server. The server receives the data and stores it in the database. The server design uses the web framework: Struts2+Spring+Hibernate+JSP+JFreeChart, and the JDK version is jdk 1.7. The database server platform uses MySQL 5.5, which shares the same database with the server monitoring program to achieve data sharing [15]. The PC software function module is shown in Figure 6.
4. Experiment and application
In order to verify the feasibility of the remote monitoring system of the contact network compensation device, the wire ends of the wire-type sensor 1 and the wire-type sensor 2 are respectively fixed on the bearing line of the bearing cable and the contact line, and the other end of the sensor is fixed on the bracket, the site The installation diagram is shown in Figure 7. Manually measure the ambient temperature values ​​at different time points, the length values ​​of the pull-wire sensor 1 and the pull-wire sensor 2, and compare them with the data monitored by the Web server. The experimental data is shown in Table 2. The test results show that the sensor measurement data is more accurate and the solution is feasible.
5 Conclusion
We designed and implemented a complete catenary compensating means remote monitoring system, the system controller C8051F930 chip as the main system, as a communication module to SIM900A node of the wireless sensor network, between nodes at different times The data is sent to the server at intervals, combined with GPRS wireless communication and Web server technology to connect the node to the remote server. By monitoring the ambient temperature and the change of the length of the contact cable and the contact line, it is judged whether the contact compensation device is stuck. The system is tested and can find fault points quickly, timely and accurately.
references
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