Abstract: This article addresses the problem that industrial control computers (ICCs) in coal mine automatic control systems cannot be directly used underground. A more general solution is proposed: placing the ICC, which lacks explosion-proof capabilities, above ground and utilizing the transmission channel and explosion-proof isolation performance provided by the J31 type mining ring network access device to achieve monitoring and control of underground equipment. Keywords: Coal mine; Explosion-proof; Industrial control computer; Industrial Ethernet; Access device; Communication interface; KJJ31 0 Introduction A crucial issue to be addressed in coal mine automation is the explosion-proof protection of underground equipment. The ICCs used in coal mine automation systems are non-explosion-proof and cannot be directly used underground, posing significant challenges to the design of such systems. This paper introduces a method using the KJJ31 type mining ring network access device to solve this problem. 1 Main Technical Parameters and Functions of the Ring Network Access Device The KJJ31 type mining ring network access device is a data exchange and transmission device developed by the Changzhou Automation Research Institute of the China Coal Research Institute. It provides an underground transmission channel for equipment with Ethernet or RS485 communication interfaces. The explosion-proof type of this access device is mine-use explosion-proof and intrinsically safe, suitable for environments with gas and coal dust explosion hazards. The block diagram of the KJJ31 mine ring network access device is shown in Figure 1. The main technical parameters of the KJJ3I mine ring network access device are: (1) The power supply is any one of four AC power sources: AC127, 220, 380, and 660V, with an allowable voltage fluctuation range of 75-115%. This provides great convenience for underground power supply. (2) It provides two redundant fiber optic Ethernet ports to connect with other ring network access devices to form a redundant Ethernet ring network; it provides six transmission communication ports, of which two are intrinsically safe Ethernet electrical interfaces, and four communication ports can be configured as intrinsically safe Ethernet electrical interfaces, intrinsically safe RS485 communication interfaces, or RS232 communication interfaces according to actual requirements. (3) The internal device uses a battery. When AC power fails, it automatically switches to battery power supply and ensures that the working time is not less than 2 hours. 2. Application of Ring Network Access Devices in Underground Coal Mines Utilizing the transmission interface and explosion-proof isolation performance provided by the KJJ31 mining ring network access device, industrial control computers (ICCs) without explosion-proof capabilities can be placed anywhere above ground with a network interface to monitor and control underground equipment. The following section uses the specific application of the KJJ31 mining ring network access device at Qianjiaying Mining Branch as an example to illustrate its application in underground coal mines. Currently, Qianjiaying Mining Branch has three underground automation systems using the KJJ31 mining ring network access device: a 600-level underground shaft winch automatic control system, an -850 substation automatic control system, and an -850 water pump automatic control system. The transmission interface of the underground shaft winch automatic control system is an intrinsically safe RS232 serial port, while the other two systems use intrinsically safe Ethernet interfaces. The ICCs in these three automation systems are all located above ground, using the transmission channels provided by the KJJ31 mining ring network access device to monitor and control the underground equipment. Specific implementation methods: (1) Place two KJJ31 mining ring network access devices at the -600 level and -850 level in the mine. Lay optical cables from the surface through the auxiliary shaft to the -600 level underground shaft winch and the -850 level water pump room, and connect them to the two redundant fiber optic Ethernet ports of the two KJJ31 mining ring network access devices. The two KJJ31 mining ring network access devices then become network switching devices in the local area network. (2) The -850 substation automatic control system and the -850 water pump automatic control system have their own Ethernet modules. As long as a fixed IP address is set for the Ethernet module in each system, the industrial control computer on the surface can establish network communication with it through the KJJ31 mining ring network access device. (3) Since the -600 level underground shaft winch automatic control system does not have an Ethernet module, it can only be connected to the KJJ31 mining ring network access device through the intrinsically safe RS232 serial port. First, add an RS232 to RS485 converter to the RS232 serial port of the underground shaft winch automatic control system. Then, connect the converter to the intrinsically safe RS485 serial port of the KJJ31 mining ring network access device using a cable. Install the driver program for the KJJ31 mining ring network access device on any networked industrial computer above ground. This driver program maps the RS485 interface of the Ethernet/RS485 conversion unit to a virtual COM port on the industrial computer. The industrial computer can then monitor and control the serial devices connected to the Ethernet/RS485 conversion unit through this virtual COM port, thus establishing serial communication between the industrial computer and the underground shaft winch automatic control system. After establishing communication channels between the three underground automatic control systems and the above-ground industrial computer via the KJJ31 mining ring network access device, these three underground automatic control systems can be networked, allowing monitoring and control of the three underground automatic control systems from any networked microcomputer. By applying the KJJ31 mining ring network access device, not only are the original functions of the underground automation system unchanged, but the functions of the underground automation system are further expanded. 3 Conclusion This paper proposes a more general solution to the problem that the industrial control computer in the coal mine automatic control system cannot be directly applied underground. That is, the industrial control computer without explosion-proof performance is placed above ground, and the transmission channel provided by the KJJ31 mining ring network access device and its explosion-proof isolation performance are used to realize the monitoring and control of the underground equipment by the industrial control computer. This method is of great significance to the promotion and application of underground industrial Ethernet ring network technology in coal mine automatic control system. References: [1] Wang Jinbiao. Computer Control System [M]. Beijing: Tsinghua University Press, 2004. [2] Chen Zenghan. Industrial PC and Measurement and Control System [M]. Beijing: Machinery Industry Press, 2004. [3] Zhang Xingguo, Zhu Longbiao, Liu Ming. Application of PIC in the transformation of NH type kneader control system [J]. Automation Technology and Application, 2004 (II). [4] Li Xing, Zhu Xiaofang, Li Yanhui. Application of PLC in the electrical control system of electric traction coal mining machine [J]. Industrial and Mining Automation, 2004(5). Click to download: Application of KJJ31 type mining ring network access device in underground coal mines. Editor: Chen Dong