Comprehensive information system for underground mine safety and risk avoidance based on the Internet of Things (I)

Traditional underground mine information platforms are often built based on a certain demand (such as video surveillance, human-machine positioning, voice communication, environmental measurement and control, underground automation equipment measurement and control, etc.). The system construction technology platform, data protocol and interface specifications cannot be unified, the systems cannot be linked, and integration is difficult. Most of them can neither meet the comprehensive data sharing and decision-making support of mines, groups, and government departments for the production process of the mining industry, nor meet the safety management needs of the mining industry.

　　At present, underground data transmission networks mostly use wired transmission. Due to the characteristics of continuous excavation in mines, wired networks are difficult to deploy quickly and mobile. Production management departments cannot obtain information from the front line in real time and cannot provide effective support for production, safety, and scheduling on the front line.

　　With the deepening of digital mining, there is an urgent need to establish a digital mine management support platform based on the Internet of Things, forming a platform that can provide comprehensive and effective data sharing and operational decision-making support for all production management and safety management links that can instantly reflect the front-line production site.

　　The goal of this project is to complete the mine underground safety and risk avoidance integrated information system based on the Internet of Things, so that it can take advantage of the advanced nature of the Internet of Things technology to provide a unified management and decision-making support platform for mine safety management and production process control. Through the storage and analysis of various types of data of the entire mine, it will eventually realize and provide personnel and vehicle positioning management, IP dispatching and command systems, underground intelligent traffic signal control systems, emergency evacuation broadcast systems, environmental monitoring systems, production process control systems, mine virtual reality systems and other industrial control applications, and establish the standardization of Internet of Things applications in the mining industry and the data transmission protocol and interface specifications.

　　Construction requirements

　　Personnel (vehicle) positioning: to achieve accurate and continuous positioning of the main production areas, main transport lanes, and main ventilation lanes in the mine; to achieve accurate and continuous positioning of vehicles passing through the mine;

　　Voice communication: realize wired voice communication at fixed points underground, achieve full WIFI coverage in the main production area, and realize wireless communication underground;

　　Dispatching and commanding: realizing voice and SMS dispatching of underground personnel and voice dispatching of underground vehicles;

　　Video monitoring: realize underground fixed digital video monitoring and mobile video acquisition in the underground WIFI coverage area;

　　Online monitoring of production environment: realize online monitoring of environmental parameters such as carbon monoxide and wind speed at fixed locations, and realize wireless real-time online monitoring of underground safety personnel’s handheld devices;

　　Ramp traffic signal control: underground ramp trackless transportation traffic signal control system;

　　Expandable applications: ventilation automation system, drainage automation system, power supply automation system, equipment status monitoring, rail transportation signal collection and closing system, etc.

　　System Architecture

　　The underground safety and risk avoidance comprehensive information system based on Internet of Things technology is a comprehensive information platform that integrates industrial Ethernet ring network technology, ZigBee wireless positioning and wireless data transmission technology, WIFI wireless communication technology, VOIP voice communication technology, geographic information system technology, management information system technology and database technology. It will enable mining enterprises to achieve comprehensive perception and mine production scheduling and command, realize visualization, automation and information management, and realize the connection of the Internet of Things - perception of mines.

　　The system mainly consists of several subsystems: industrial network subsystem, human-machine positioning subsystem, communication subsystem, and monitoring subsystem.

　　Industrial Network Subsystem

　　Combined with the actual situation of the mine, the whole system adopts a network communication subsystem integrating multiple technologies, which includes several main parts: industrial Ethernet ring network, wireless horizontal communication subsystem, and wireless integrated substation.

　　Industrial Ethernet Ring

　　As the core network of the entire mine, the industrial Ethernet ring network carries the large-volume transmission of all industrial automation, video surveillance, human-machine positioning, environmental monitoring and other data in the mine, as shown in (Figure 1).

　　The deployment of industrial Ethernet ring network meets the following design conditions.

　　1. The industrial Ethernet ring network should meet the Gigabit data bandwidth, meet the data transmission requirements of various applications underground, and reserve sufficient expansion margin;

　　2. Cover all important hubs and electromechanical equipment sites such as hoisting systems, production mid-section horse head gates, fan rooms, mining area substations, explosives depots, pump rooms, etc. (combined with the surface production system to form an industrial Ethernet ring network for the entire mine);

　　3. Reserve interfaces to meet future expansion needs;

　　Industrial Ethernet ring network trend description: The underground industrial Ethernet ring network adopts a double ring network architecture.

　　Wireless horizontal communication subsystem

　　Wireless integrated substations are used to cover the horizontal main lanes and ramps in the middle sections of each production area. A substation is deployed every several meters to achieve dual wireless network coverage of WIFI and zigbee, as shown in (Figure 3).

　　The wireless horizontal communication system adopts the world's leading wireless technology, and the wireless substation adopts the latest WIFI wireless technology and a zigbee positioning module. Since the product has two optical fiber modules, the entire wireless backbone core network adopts a "back-to-back" two-layer transparent relay method to form a hybrid horizontal communication link of wired and wireless, with high bandwidth, low system delay, and stable operation of the wireless backbone link, which can withstand various applications such as environmental collection, personnel positioning, voice communication, video monitoring, etc.

　　The characteristics of wireless substation networking are: transparent transmission machine to create a stable and high-speed wireless link; perfect redundancy design; seamless roaming of wireless mobile phones; use of special polarization antennas; synchronous NTP self-maintenance mechanism; dynamic TDD (time division duplex); two-way dynamic adaptive modulation; adjustable ACK delay (ACK Timeout); OFDM technology.

　　Wireless integrated substation self-healing ring technology: The wireless base station supports automatic detection and switching of the loop. Both ends or multiple sections of the wireless link are connected to the industrial fiber-optic Ethernet ring network that has been built in the mining area. The wireless link and the industrial fiber-optic Ethernet network form a ring or a tangent ring. When a faulty node appears in the wireless link, the system can immediately switch the chain direction to ensure that the system service is not interrupted. Each device in the entire wireless link can be used as a fiber optic access point to ensure that the system runs effectively and reliably, and the service is not affected when the system is maintained.

　　Network access to the mining site: (This part is a bit strange. If wireless network is used, why do we need to use copper wires for access?)

　　For the network access of the mine, considering the short mining cycle, complex environment and easy scratching, the optical cable access solution requires large equipment investment, long construction cycle, difficult maintenance and cannot be recycled. This system adopts copper wire access for the mine network access.

　　Solution 1: If only personnel (equipment) positioning is required in the mining area, the CAN bus communication method is adopted, and two copper wires are used to connect the locator in series and lay it in the mining area.

　　Solution 2: If comprehensive applications such as video, voice communication, broadcasting, positioning, emergency alarm, and CO monitoring are required in the mining area, telephone line ADSL is used in conjunction with underground intelligent terminals in the mine to achieve mining area access.