Abstract: This paper addresses the challenge of seamless integration between the physical layer and the protocol layer (software layer) of existing automated subsystems in the construction of a comprehensive automation system for a coal mine. The differing hardware interfaces and communication protocols of these subsystems present a problem when connecting them to an industrial Ethernet ring network. This paper discusses this issue and proposes corresponding solutions. Keywords: Industrial Ethernet; Interface; OPC; DDE/NetDDE In recent years, with the rapid development of automatic control and computer network technologies, comprehensive automation systems for coal mines have been widely applied. A comprehensive automation system integrates the mine environmental monitoring subsystem and the automatic control subsystems of various production processes through a high-speed industrial Ethernet ring network and automation platform software. It connects to the mine-level management system via a firewall to achieve integrated management and control of the entire mine. Because existing coal mine automatic control subsystems, such as environmental safety monitoring systems, conveyor belt control systems, power supply monitoring systems, rail transport monitoring systems, and personnel tracking and positioning systems, use different hardware interfaces and communication protocols, achieving seamless integration between these subsystems and the industrial Ethernet ring network is a primary challenge in constructing a comprehensive automation system for a coal mine. How can seamless integration of various automatic control subsystems with the industrial Ethernet ring network be achieved? In short, it involves resolving the access issues at both the physical layer and the protocol layer (software layer) of the industrial Ethernet ring network. In a comprehensive mine automation system utilizing industrial Ethernet ring network technology for fieldbus integration, physical layer access refers to various devices being equipped with Ethernet cards or conversion interface cards to enable communication that supports Ethernet standards and TCP/IP protocols. Currently, commonly used physical interface types in coal industry automation control systems include: RS485 interface, fieldbus interfaces (such as Profibus, Modbus, LanWork, CAN, etc.), PLC programmable controller interface, RS232/485 serial port, host computer/operator station, etc. The conversion between these physical interfaces and industrial Ethernet is shown in Figure 1. While completing the physical layer interface conversion, the access issue at the protocol layer (software layer) also needs to be considered. Since the upper-layer protocols of different subsystem manufacturers differ, support for multiple communication protocols should be fully considered in data acquisition; therefore, corresponding data acquisition interface programs must be configured for data acquisition. Currently, the commonly used software protocols in the automatic control subsystem of the coal industry include: OPC/DDE, CAN, Siemens PLC, proprietary protocols based on the 485 bus, file-based data exchange, non-standard protocols based on serial communication, and data acquisition based on database access. Commonly used standard interfaces for data acquisition include: (1) OPC interface. OPC (OLE for Process Control) is a standard widely followed in the industrial control field. It specifies the interface protocol for data access between application programs and field devices or data sources. It is designed based on Microsoft's component technology (COM/DCOM) and adopts a client/server architecture. It can access data from local OPC servers and OPC servers distributed on other nodes on the network, and has the characteristics of high efficiency and security. (2) DDE/NetDDE interface. NetDDE is a network-based dynamic data exchange (DDE) technology. DDE was released by Microsoft in its early days to solve the dynamic exchange of data between application programs. It also adopts a client/server architecture. It can access data from local DDE servers and DDE servers distributed on other nodes on the network. It is inferior to OPC in terms of speed and security. (3) ODBC interface. Some control systems have a host computer system with database support, which periodically writes data into tables in a shared relational database (such as MSAccess or MSSQL). The data integration platform can access the database through the ODBC interface to obtain the data. However, this data acquisition method cannot guarantee the real-time performance of the data. For the acquisition of data from automatic control subsystems using different software protocols, the following methods can be used: (1) Data acquisition through the OPC/DDE interface. For automatic control subsystems with OPCServer functionality, AgilorDAForOPC/DDE is installed on the host computer (the machine providing OPCServer functionality) of the system, and it is used as an OPCClient to connect with the OPCServer of the centralized control system for real-time data acquisition. (2) Data acquisition using PLC control system. For automatic control subsystems using PLC, an Ethernet communicator is installed, and I/O variable data is acquired in real time through configuration software, such as installing AgilorDAForOPC on the commonly used WinCC data acquisition server, and using it as an OPCClient to connect with the OPCServer of the WinCC data acquisition server for real-time data acquisition. (3) Data acquisition through RS485 interface. For automatic control subsystems that use RS485 transmission but cannot provide OPCServer functionality, RS485 can be directly connected to the industrial Ethernet ring network node. An RS485 driver and Agilor DA For RS485/232 are installed on the ground data acquisition workstation, and real-time data acquisition is performed according to the data protocol agreed upon with the subsystem manufacturer. Alternatively, all data from similar subsystems underground can be aggregated in the dispatch room and then converted to RS232 through the data transmission interface and connected to the host computer of the system. (4) Data acquisition through fieldbus interface. For automatic control subsystems that use fieldbus but cannot provide OPCServer functionality, RS485 signals can be converted to Ethernet protocol by installing a multi-functional substation. An RS485 driver and Agilor DA For CAN/Modbus are installed on the ground data acquisition workstation, and real-time data acquisition can be performed directly. Currently, Agilor real-time database supports direct acquisition of the following bus data: LonWorks, Modbus, FF, ControlNET, CAN, BACnet, Profibus, etc. (5) Data acquisition through RS232/422/485 serial port. For devices that directly provide serial communication, a multi-functional substation can be installed underground to convert RS232/422/485 signals to Ethernet protocol. RS232/422/485 drivers and AgilorDAForRS232/422/485 can be installed on the ground data acquisition workstation, enabling direct serial communication for real-time data acquisition. (6) Data acquisition via file interface. For systems that cannot provide a direct interface, an FTPServer and AgilorDAForFile can be installed on the ground data acquisition workstation. By agreeing on file formats and access control mechanisms with the subsystem vendor, data can be acquired via files. Summary Only by using the above methods and solving the problem of seamless access between each automatic control subsystem and the industrial Ethernet ring network can the information sharing and resource sharing functions of the mine integrated automation network platform be truly realized, ultimately achieving the goal of intensive, efficient, and integrated automated mine construction. Click to download: Discussion on the Access Problem between Coal Mine Automatic Control Subsystem and Industrial Ethernet Ring Network