In recent years, frequent accidents in China's coal mining industry have brought heavy disasters to the country and the people. How to strengthen the safety production and supervision work, how to improve the efficiency of search and rescue work after the accident has become a hot issue of social concern. This paper closely combines the actual needs of the coal industry to design a smart identification card, which combines radio frequency identification technology, network communication technology and automatic sensing technology to solve the safe operation of equipment under the mine, long-distance transmission of data, and signal conversion. And technical problems in information processing, etc., provide effective scientific and technological support for mine personnel monitoring, control and tracking management, rescue and disaster relief, and efficient operation of safety and rescue.
1 Device configuration
The communication between the smart identification card and the base station is carried out by means of radio frequency identification technology (Fig. 1). Radio frequency identification technology is a technology that uses radio frequency signals to realize contactless information transmission through spatial coupling (alternating magnetic field or electromagnetic field) and achieve the purpose of identification through the transmitted information [1]. There is no mechanical movement mechanism and electrical contact between the identification card and the base station, and the operation is convenient and fast, the reliability is high, the service life is long, and the anti-interference is strong.
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1.1 Design of smart identification card
In the mine personnel positioning system, the design of the identification card is divided into: a processor module, a liquid crystal display module, a keyboard operation module, a wireless transmission module and a sensor module. Based on these large modules, an automatic alarm function can also be designed. The overall design of the smart identification card is shown in Figure 2.
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1.2 RF chip selection
The wireless communication frequency of coal mine personnel positioning is usually 433 MHz and 2.4 GHz in China's free frequency band. The available chips are CC1100, CC2510 from CHIPCON, nRF905 (nRF9E5) and nRF2401 (nRF24E1) from Nordic. The CC1100 and nRF905 generally select the 433 MHz band, while the CC2510 and nRF2401 generally select the 2.4 GHz band. CHIPCON's chips use general RF technology and cannot be frequency hopped. In order to improve the anti-interference ability as much as possible, this paper selects Nordic's chip with frequency hopping function. nRF9E5 (nRF24E1) is an integrated system C51 microcontroller and nRF905 (nRF2401) system-on-chip [2], its function is the same as nRF905 (nRF2401), but the experiment generally does not use nRF9E5 (nRF24E1), because it requires a special program downloader, use is not Convenience. The RF in the 433 MHz band has a strong penetration capability in the mine, and its transmission effect is better than in the 2.4 GHz band [3]. However, the transmission performance is good and the bandwidth is relatively reduced. Generally, the nRF905 has a transmission rate of 100 kb/s. If video and voice are not transmitted, the nRF905 is an ideal choice. Therefore, the nRF905 chip is used in this paper.
1.3 nRF905 chip
nRF905 is a single-chip RF transceiver from Nordic VLSI, Norway. It operates from 1.9 V to 3.6 V in a 32-pin QFN package (5 mm × 5 mm) and operates at 433/868/915 MHz 3 ISMs (Industrial, Science and Medicine) Channel. The nRF905 consists of a frequency synthesizer, a receiver demodulator, a power amplifier, a crystal oscillator and a modulator. It does not require an external sound table filter, automatic processing of the header and CRC (Cyclic Redundancy Check), using the SPI interface and micro Controller communication, configuration is very convenient. In addition, its power consumption is very low, built-in idle mode and shutdown mode, easy to achieve energy savings. The nRF905 provides a powerful frequency hopping mechanism and a large number of channel support, and even with a gain-free PCB antenna, the transmission distance can reach 200 m. If you need to transmit longer distances, you can use an antenna with gain, and the transmission distance can be extended to more than 1 km.
1.4 Circuit Design
According to the characteristics of the MCU and the design requirements of the nRF905 interface, the P0.23 and P0.22 of the MCU are connected to the TRX_CE and TX_EN of the nRF905 respectively to control the working mode of the nRF905. P0.24 is connected to the CD of nRF905, thereby judging whether nRF905 detects the carrier; P0.25 is connected to the AM end of nRF905, thereby judging whether the sending destination address of the sender is the same as the local address; the external interrupt 0 of the MCU is connected to nRF905 The DR end determines whether the transceiver data is completed. The SPI port of nRF905 is connected to the corresponding port of SPI0 of the MCU to realize the working configuration and data transmission of nRF905. The uPCLK of nRF905 provides the reference clock output, and the output frequency of the oscilloscope is observed to judge the nRF905. The configuration is correct. The interface circuit of nRF905 and MCU is shown in Figure 3.
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2 Design of underground personnel positioning system
2.1 Design principles of the positioning system
(1) Realize the effective identification of the entry and exit of the working face of the underground tunnel, and effectively monitor and warn the environment, so that the system management fully reflects “humanization, informationization and high automation†[4].
(2) Provide senior management personnel with information inquiry on various aspects such as attendance operations and personnel access restrictions.
(3) In the event of a safety accident, the system can immediately know the number of staff on the tunnel working surface and ensure the efficient operation of rescue and disaster relief and safety rescue work.
(4) After the occurrence of a safety accident, the mobile identification device of the system can detect whether there is anybody within 10 m of the accident site, which facilitates the timely deployment of the ambulance work.
(5) The system design is safe, expandable, easy to maintain and easy to operate.
2.2 Overall design
The overall design of the system is shown in Figure 4. The hardware system is mainly composed of an identification card, a recognition base station, a relay station (bridge), a transmission interface, and the like. The wireless communication uses the nRF905 chip, and the underground wired communication uses the CAN bus and network technology. The design of the software system is mainly the design of the upper computer software and the lower computer software. The main design functions of the software include: real-time data acquisition, real-time data display, historical data query, personnel monitoring and query function, timeout alarm function, statistical attendance, data history preservation, system maintenance, etc.
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2.3 Functional design of the system
(1) Data collection and early warning
The smart identification card keeps the identity code of the underground personnel and can detect the gas concentration in the mine. When the concentration reaches the set limit, the smart card will automatically alert to remind the underground personnel to evacuate urgently. There is also a keyboard and display on the smart identification card for use by underground personnel. This smart card is carried by the staff.
Under the mine, along the roadway, a detection base station is arranged at a certain distance. In addition, monitoring base stations can be installed at the entrances, intersections, working faces, dangerous places (such as blind lanes) of the mine roadway, and the main entrances and exits of the ground. . When the person carrying the smart identification card enters the detection range of the monitoring base station, the identification card transmits the collected downhole data, personal identity and operation information to the base station, and the base station receives the data and sends it to the uphole control center for processing through the CAN bus. The control center can also send an indication to the downhole personnel, and the identification card displays on the display after receiving the indication.
(2) Personnel tracking
In the database of the uphole monitoring host, the precise position information of each positioning device under the mine is saved. When the downhole personnel are located in the roadway where the downhole positioning device is laid in advance, during the data acquisition process, it is possible to determine which base station sends the information, so that it can be determined between the two fixed base stations, and then through the database By the location information of the two fixed base stations, it is possible to know which section the person is in and display it in real time through the electronic map on the computer, so that the manager can query various information in time.
(3) Post-disaster rescue function
In the event of various types of accidents, the monitoring host can immediately display the number of personnel in the emergency location, personnel status, personnel location and other information, providing a basis for the development of rescue and rescue plans, greatly improving the efficiency of rescue and rescue effects; prohibiting certain special areas Setting, when there is illegal entry, the monitoring software will immediately start the alarm system of the entrant carrying the identification card; in case of emergency, the emergency help information is sent to the control center through the button of the smart identification card.
(4) Integrated information management
The system can automatically and accurately count miners' time into wells and raise wells, and generate corresponding attendance records and statistical reports; reflect the flow routes and locations of underground personnel in real time, effectively supervise the personnel entering the wells, effectively improve the safety production prevention ability [5], and promote safe production. . In system maintenance, different permissions are assigned to operations and management personnel to ensure system security.
The computer network can realize the data sharing of the mine target positioning safety management information, and provide real-time monitoring information and historical information for the leaders of all departments and the lower and upper levels in the mine, providing an important basis for command and decision.
The design proposed in this paper has been successfully applied to a mining group in Heilongjiang. The system works stably and works well and has proven to be suitable for use in complex environments under mines. The human-loaded smart identification card adopts the nRF905 radio frequency chip. Because the nRF905 chip has a frequency hopping mechanism and a large number of channel support, it solves the problem that the signal transmission is limited by environment and distance and the single frequency band of the wireless signal transmission. At the same time, the card has built-in gas sensor, automatic alarm, keyboard and liquid crystal display. It is conducive to mine safety first aid and improve production management efficiency. This design provides effective technical support for the efficient operation of underground mine personnel monitoring, control and tracking management, rescue and disaster relief, and safety rescue.
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