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!

• 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.