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1. Overall consideration:
At the lowest possible cost, it can effectively and reliably realize the basic functions of underground personnel wireless positioning and working environment monitoring, and further improve and increase the functions of the system on this basis. Therefore, this program will make use of the existing communication facilities and conditions underground as much as possible. In addition, in order to reduce the number of base stations used for reading and writing positioning to reduce costs, personnel positioning uses the divisional time and attendance positioning method (this is also the current method commonly used in underground coal mine personnel positioning). Of course, the accurate positioning method with full signal coverage can also be used ( Need more reader base stations). Thus, bring you higher efficiency! More returns!
2. Existing positioning methods:
1. Radio frequency card (RFID) attendance system:
At present, the tracking of underground personnel basically adopts this method. This method is actually at the entrance of the mine, using radio frequency card (RFID) reading (swiping card) method to register and record the underground personnel to track the method. In fact, this is not personnel tracking in the true sense, and it is impossible to report the specific location of underground personnel in real time. There are several problems with this method:
● Long-distance radio frequency card reading and writing systems are very expensive, large in size, and are subject to certain restrictions on installation and use. In terms of cost, it is unrealistic to install many such card reading systems underground;
● The transmit power of the read-write system of this kind of system is generally large, which often exceeds the limit of the safety regulations for underground use, so it is often not installed in the underground;
● The card reading speed of this system is very limited, and it cannot handle the situation where multiple people pass the card reading system quickly at the same time (such as going down the well by car). At this time, the system often misses reading;
If using a long-distance card reading system;
● Due to the frequency and communication method used by this system, the anti-interference performance is very limited, and there are also problems when using it in a complex underground environment;
● The conclusion is that the general RFID radio frequency reading and writing system cannot realize the real tracking of downhole personnel, and cannot report the specific location of downhole personnel in real time. It can only be used as attendance registration for downhole personnel.
2. The underground personnel tracking system based on the general narrow-band source electronic tag, represented by super RFID:
This system is actually not a real RFID reading and writing system at present, but a low-power micro-power wireless transceiver system. The problem is:
● Because the system uses a narrow-band point-frequency working mode, the working frequency is very narrow, and because the crystal oscillator’s natural frequency itself drifts due to temperature changes (temperature drift), and changes over time (aging), so The frequency of the entire system changes and drifts beyond the operating frequency of the system. Thereby, the reliability and stability of the system work are problems.
● Although compared with the general radio frequency card reading and writing system RFID, the reading distance is greatly improved; however, due to the low receiving sensitivity of the system, between -80dBm and -90 dBm, the transmit power of the reader is only 1/1000 Watt, a typical example is the NRF2401E chip from Nordic. Therefore, there is a problem of insufficient communication distance, especially in industrial sites with large interference in coal mines.
● Since there is no direct sequence spread spectrum anti-jamming technology, compared with wireless communication systems that use direct sequence spread spectrum technology, it is obviously lacking in anti-interference ability. Therefore, work in many places with strong interference in underground mines. The reliability will be greatly reduced. You can’t even communicate at all.
● Due to the problems with the read-write distance and reliability of this system, it is required to locate the reader in accordance with the relevant regulations of the State Administration of Work Safety. When 80 miners pass the reader at the same time at a speed of 5 m/s, the reading The writer must record them without omission. If the reading and writing distance of the reader is not enough, the miner’s time in the signal coverage of the reader is very limited, and because of the error caused by interference, a correct signal often needs to be sent multiple times. Therefore, the system is difficult to meet this requirement. Require.
● The reader/writer of this system is also very expensive, so the investment in the construction cost of the system is very high.
● The conclusion is that, no matter from the economic point of view, the reliability of the system, and the practicality, the general narrowband point-frequency communication system is not suitable for underground personnel positioning system.
System.
3. Using our new generation Super-Zigbee network wireless positioning system for underground personnel in mines:
1. System introduction:
The new positioning system is a simple, cost-effective and effective positioning system developed on the basis of today’s latest Zigbee technology. It fully meets the new regulations of the State Administration of Work Safety on the management of underground coal mine operators in 2007. Refer to the document “The People’s Republic of China Safety Production Industry Standard AG 6210 -2007 General Technical Requirements for the Management System of Underground Workers in Coal Mines. AQ1048 -2007 Specification for the Use and Management of the Management System for Underground Workers in Coal Mines”. In order to reduce the cost of the entire system and start from the specific environment of the underground coal mine, the new underground coal mine personnel positioning system adopts the “divisional positioning” method, that is, according to the management requirements and the actual situation of the underground site, the underground is divided into several areas. Each area is controlled by several entrances and exits. For example, the two ends of a section of a single roadway are the two entrance and exit control openings of the section of the roadway. Some areas may have more than two entrance and exit control openings. In order to determine the number and specific list of operators in each area at any time, we must know the number and specific list of all personnel who control the entrance and exit through the area. If we install electronic tag readers at each control entrance and exit, this requires that the reader can record all the electronic tags passing through the entrance and exit without leakage. At the same time, we must also distinguish each electronic tag. Direction of entry and exit. To this end, we will install two directional readers with opposite reading and writing directions back to back at each entrance and exit (see the photo below).
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Short range reader
Each reader is connected to a communication cable laid down in the well through a serial port (such as RS232/RS485), and is connected to the control center computer. Each directional reader can receive electronic tag signals within a distance of not less than 100 meters, and within this 100 meters, the direction of the electronic tag is not restricted. The electronic tag sends out its own identity code information every 2 seconds. After the reader receives the information, it will be stored together with the corresponding received signal strength and the sequence of reception, and a certain period of time such as 10 seconds , Pack all these information, plus the reader number, and pass it to the control center computer through the underground communication network. Using these raw data information and artificial intelligence logic standards, and using location information preprocessing software to process, a list of operators in any area of the mine at any time will be provided to the host computer. This location list, It will be updated every 30 seconds in accordance with the provisions of the above-mentioned national documents.
Using this location data, the host computer software can provide users with the specific location of any person in the underground at any time; at any time, the list of operators in any area of the underground.
In places where there is no wired communication network laid down in the mine, our readers can also transmit the read information to the The wireless receiver connected to the wired network (see the figure below) is then transmitted to the management center computer.
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Long-distance reader/relay transmission module
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Directional antenna
In summary, the overall system operation principle diagram is as follows:
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2. Some specific details:
● Every mobile target that needs to be located (such as a miner) needs to carry a wireless identity card module or a fully enclosed electronic tag fixed on a safety helmet. The transmission power of each tag is less than 1/1000 watts. It is recommended to use Our simplified function SL2420A, or low-cost SL2435A module:
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(Smart electronic tags carried by underground workers)
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(Card-type electronic label module (SL2426A) size: 40 x 20 x 3 mm)
What we need to explain here is: the card-type electronic tag in the photo is used in the well. When used in the well, the user needs to design the anti-riot packaging by himself and use the corresponding battery (polymer lithium battery);
● In order to increase the battery life, the wireless identity module transmits an identity code signal every 2 seconds. In order to avoid the interference of the underground environment on the wireless signal, all wireless identity card modules use anti-interference direct sequence spread spectrum communication method; at the same time, in an emergency, you can also send out emergency messages at any time through the button on the card;
● We can also use this wireless personnel positioning system to monitor the working environment in coal mines. For example, using our company’s long-distance wireless temperature collector, the temperature of the working point that needs to be monitored can be transmitted wirelessly. Provide a read-write locator 500 meters away, so that not only can it be flexibly collected at different locations (especially the mining surface) according to needs, various information required for safe production (for example, temperature, gas concentration, wind pressure and wind speed) Etc.), while automatically transmitting the location information and related information of the collection point to the monitoring center. This kind of gas collection point can be placed in a fixed position on the mining surface and move with the movement of the mining surface, and it can also be carried by the gas security inspectors, which is very convenient. When the gas concentration exceeds the standard, the wireless module can immediately transmit the concentration to the management center computer through the network. Our wireless temperature sensor is only the size of a matchbox, and it can work for more than 3 years without changing the battery using a AA lithium battery. It can also send other sensor data to the management center computer. When necessary, other linked emergency equipment will be activated at the same time.
Note: All equipment used in our system, in terms of circuit design itself (maximum capacitors, power, etc.), meets the requirements of underground riot control. We can provide relevant information for customers to apply for intrinsic safety certification.
http://www.sutel.cn/
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