Design of coal mine lighting and safety monitoring system based on LED technology

In recent years, coal mine production safety accidents have occurred frequently, resulting in the serious phenomenon of "major accidents are frequent and minor accidents are continuous", which not only seriously threatens the lives of miners, but also seriously restricts economic development. Underground coal mine operations are far away from the ground, with complex terrain and harsh environment, leading to frequent accidents. At the same time, the state's management of coal mine safety production is constantly strengthening, and various units are carrying out the construction and transformation of digital mines, and have achieved certain economic and social benefits. In recent years, new technologies including remote video monitoring, remote mine information collection, and identity recognition based on RF ID technology are being rapidly applied to the field of coal mine safety production, which plays an important role in improving the safety environment of coal mines and establishing real-time supervision and management. In order to fundamentally solve the problem of coal mine safety, it is necessary to rely on scientific and technological means to improve the overall safety technology equipment and management level of coal mines. Establishing a set of safe, real-time, economical, reliable and complete safety monitoring platforms and safety management systems is an effective measure to prevent coal mine safety accidents and ensure long-term stability.

1 LED technology and its advantages in mine applications

LED (Light Emitting Diode) is a semiconductor component that converts electrical energy into visible light . It changes the principle of tungsten filament light emission of incandescent lamps and tri-color light emission of energy-saving lamps. It uses electric field light emission and is a cold light source with no flicker and a color temperature close to that of sunlight. It can effectively protect the eyesight of underground workers and completely avoid gas explosion accidents caused by ordinary lighting lamps. LED is powered by a low-voltage DC power supply with an operating voltage between 6 and 24 V. It is safer and more economical than using a high-voltage power supply. Its power consumption is only 30% of that of traditional incandescent lamps, which can effectively save energy. In addition, it has the characteristics of fast response time, good stability, long working life (> 100,000 hours) and maintenance-free. In the mine, ultra-bright white LED strips can be installed to provide tunnel lighting; red, green, yellow, and orange LEDs can also be installed to mark interval distances, monitoring points, forks, safe evacuation routes, early warnings, alarms, and other information; battery backup power supplies can be configured at appropriate intervals in the tunnel, so that even if a landslide accident cuts off the lighting and communication lines, local lighting and LED indication information can be ensured to help underground personnel escape.

LED power supply can use 24 V low-voltage circuit, which also provides a safe and stable power supply environment for realizing power supply and data communication of mine safety monitoring equipment (module level). It is entirely possible to establish a small communication network based on single-chip microcomputer modules to provide reliable information collection and transmission channels for monitoring modules such as gas, carbon monoxide, air volume, temperature and video information in the safe production link of coal mines; infrared coding identity recognition technology in LED technology can also be used to install infrared collection probes in LED lighting strips at appropriate intervals to collect and transmit identity information of personnel in the mine, and send relevant data to the upper computer on the ground of the mine in a timely manner, and summarize it to the production scheduling and safety monitoring server through the communication network, and form a three-dimensional, real-time personnel distribution geographic information system with management information database, mine tunnel map, etc., which can provide reliable guarantee for production scheduling, safety monitoring, rescue and evacuation.

2 System Design

FIG1 is a schematic diagram showing the distribution of a tunnel lighting and safety monitoring system implemented using LED technology in an underground tunnel.

(1) LED lighting strips and backup power supply. In Figure 1, the ribbon cable connecting all nodes and devices adopts the packaging form of the "plastic neon lamp" widely sold on the market. The white light LEDs are installed in series and parallel at equal distances, which can solve the lighting problem of the entire tunnel. LEDs have obvious advantages over incandescent lamps, such as low power consumption and long service life. It is a point light source, which makes it easier to accurately control the radiation direction and luminous area of ​​light, especially in some application fields (mines) where the lighting area requirements are not large. The use of traditional light sources often results in a waste of energy because the lighting area exceeds the actual demand. LED light sources can meet the lighting requirements without wasting energy. Due to the use of a low-voltage DC power supply solution, a backup battery can be configured every 50 meters or so, which can not only realize emergency lighting in the event of power outages or failures, but also provide evacuation instructions and local lighting in the event of power outages caused by accidents such as landslides.

(2) Road signs and evacuation route indications. Under white light LED lighting conditions, colored LED point light sources can be distributed in intervals in the light strip to indicate road signs such as distances, safe passages, forks, and evacuation routes. For example, red is used to indicate emergency evacuation routes, yellow is used to indicate attention sections, and green is used to indicate distance information of 20 m, 50 m, and 100 m; combined symbols are used to indicate traffic signs such as directions and forks; and dot matrix LED modules can be used to provide more detailed information such as directions.

(3) Identity recognition and security monitoring module. The low-voltage power supply and communication lines of the LED light provide convenient conditions for the monitoring system.

Infrared light encoding/decoding technology is used, and the infrared encoding module installed on the miner's LED lamp and the light decoding receiving probe on the equally spaced LED light strip are used to realize the management functions of underground personnel identification, attendance, tracking, and distribution location. Gas detection modules, fire detection, exhaust monitoring, video monitoring, etc. can also be arbitrarily connected to the line. These modules are designed with the latest 32-bit embedded microcontroller , integrated with RS232 and standard CAN interfaces , and with the help of the industrial CAN bus network , the real-time collection of on-site information is realized and transmitted to the monitoring center. An online monitoring management information system is purchased and built.

(4) Communication network. In the LED light strip wiring system, an industrial bus with strong anti-interference ability can be arranged in parallel. The communication network is the CANbus system. CAN is a multi-master serial communication bus. The basic design specifications require high bit rate, high electromagnetic interference resistance, and the ability to detect any errors. When the signal transmission distance reaches 10 km, CAN can still provide a data transmission rate of up to 50 Kbit/s. Using this industrial-grade communication method can ensure the reliability and real-time nature of communication data, and can also combine the characteristics of the LED power supply line. The CAN bus has good fault tolerance and can greatly reduce the cost of subsequent maintenance, repair and expansion. It is the best form of tunnel communication. The CAN bus returns to the ground and connects to the ground terminal, and the network transmission between the ground terminals and the management center can be achieved with the help of ADSL or optical fiber .

3. Composition of security monitoring system and online management information system

Figure 2 shows the structure of the security monitoring system. Various sensors , monitoring and surveillance modules connected to the CAN bus along the LED light strip are connected to the upper computer terminal on the ground through the communication concentrator at the tunnel entrance, and then connected to the monitoring center through ADSL, DDN dedicated line or optical fiber broadband network. Based on factors such as geographical distribution, the Internet network can be used to realize data and information transmission.

In the system, the working conditions of all sensors of a single coal mine and the working status of underground equipment are monitored in real time in a graphical manner. In Figure 2, each sensor displays information such as gas concentration and the start and stop status of the equipment, as well as real-time wind speed, air volume, wind direction, and change trends of the ventilation system. Gas concentration is directly related to production safety, and software design can provide real-time processing and analysis functions for relevant data such as gas concentration and change trends. The system can automatically generate corresponding thematic maps based on the collected data and make over-limit alarm prompts. In addition, mine information is closely related to spatial location information, so a software platform that can combine spatial location information with attribute data information can be introduced. Using Map Info and other technologies, with its perfect map operation functions, positioning, map navigation and various statistical analysis functions, visual production scheduling, safety scheduling and safety monitoring functions are realized. At the same time, corresponding emergency plans can be designed for major accidents such as cross-layer and cross-boundary mining, penetration of goafs, and penetration of aquifers, as well as safety hazards that are prone to occur in daily tunnel excavation and penetration. In conjunction with personnel identity recognition, information display such as attendance and positioning of underground personnel can be realized.

Using advanced software development methods, the system has a series of functions such as dynamic editing of mining engineering drawings at coal mine workstations, remote data communication, safety analysis and early warning, network supervision, rectification plan preparation, and network supervision. It can arbitrarily select and display the mining engineering drawings of the target coal mine and the corresponding coal mine, and can freely query and browse the mining engineering drawings and other production relationship diagrams for transparent overlay for spatial analysis; it can directly measure the distance on Figure 2, and can directly compile warning supervision orders at the cross-border position of the digital mining engineering drawings, and issue them in time through the network. Safety monitoring functions include online detection, gas over-limit, curve analysis and global monitoring, data query, historical curve analysis, and email processing.

4 Conclusion

The coal mine lighting and safety monitoring system based on LED technology uses new green and energy-saving LED products to build a safe and reliable coal mine production lighting environment, and fully utilizes its power distribution characteristics to build a set of digital monitoring systems that integrate road sign indication, alarm detection, personnel identification, personnel accident evacuation, mine geographic information, management and scheduling. It abandons the traditional incandescent lighting technology and has significant advantages of energy saving, safety and explosion-proof capabilities under the condition of using safe low voltage. Combined with the latest embedded microcontroller system and the CAN bus data communication platform with strong anti-interference ability, it is connected to the monitoring center server through the Internet or optical fiber, which can give full play to the performance of low power consumption, strong processing power, good compatibility, high integration, modularization, small size, reliable and safe; it is not only an underground lighting, indication and safety monitoring system, but also a safe operation online management information system, which can fully provide efficient and economical technical guarantee for coal mine safety production.