Abstract: Based on the characteristics of PLC control technology, network technology, and logistics distribution, and combined with engineering examples of modern port logistics distribution, this paper elaborates on the realization of logistics distribution automation from several aspects, including system architecture, methods adopted, functions implemented, and security assurance. It points out that logistics distribution automation is a key link in the informatization process of modern port logistics. Keywords: Logistics distribution; Control technology; Network technology; Information management 1 Introduction The status of modern ports, especially large hub ports, is becoming increasingly prominent. The operation and management of port terminals are gradually integrated with the entire transportation and warehousing distribution chain. Ports are located at the junction of land and water transport, two basic modes of transportation. The full-process, all-round system tracking management required by modern logistics activities has become a major service content, involving port functions, multimodal transport functions, cargo collection and distribution, transshipment, warehousing functions, freight forwarding and shipping agency functions, container business operation and business management functions, and management information systems. The logistics system includes two parts: the logistics operation system and the logistics information system. The former mainly includes a series of activities such as transportation, warehousing, and loading and unloading, while the latter is a system for collecting, processing, and handling various information generated along with the movement of goods. With the development of computer control technology and network technology, the modernization of production automation monitoring and management technology in traditional industries has made rapid progress. The implementation of production process monitoring and management systems and enterprise resource planning (ERP) management systems is now very common. 2 Distribution Process [align=center] Figure 1 Distribution Process Flowchart of Bulk Cement Station [/align] The Shekou Port Bulk Cement Station of China Merchants Port (Shenzhen) Co., Ltd. has an unloading capacity of 700 tons/hour and a storage capacity of 4*11,000 cubic meters. It has a 4-warehouse unloading and warehousing system, a 4-line bulk outbound system, a 4-line loading and outbound system, and a 4-line packaging and outbound system, as shown in Figure 1. Cement loaded onto ships is transported to any of the four cement storage silos via a process consisting of a ship unloader, a high-speed screw conveyor, a high-speed screw elevator, and pneumatic gate valves. Cement in the silos is then transported to any packaging silo or bulk silo via a process consisting of a high-speed screw conveyor, a high-speed screw elevator, chutes, and pneumatic gate valves. The cement is propelled by high-pressure air in the chutes. Further processing is then performed as needed, including bulk loading onto trucks, bagged packaging, or bulk loading onto ships. This creates a smooth, closed-loop distribution process within the ship, storage silos, temporary storage silos, bulk loading machine, and packaging area. 3. System Structure and Configuration The system's structural design fully considers safety, reliability, stability, versatility, and compatibility, and is designed as a distributed system. Field equipment signal levels, control levels, and central operation and management levels communicate via industrial Ethernet. The system includes two redundant central operation and management stations and two control stations. The system can also communicate with the port's management system via a reserved Ethernet interface, enabling resource sharing. The system network topology is shown in Figure 2. [align=center]Figure 2 Network Topology Diagram[/align] The central operation station uses a high-reliability industrial PC and is located in the central control room. Key technical specifications: CPU PⅣ ≥ 1GHz, ≥ 30G hard drive, 21'' color monitor, standard keyboard, 256MB memory, 3.5” 1.44M floppy drive, 40XD-CDROM, dual Ethernet cards. It performs management functions such as system operation, monitoring, alarm, recording, storage, and report generation; one unit also functions as an engineering station, handling the programming and configuration of the entire system. Two printers are configured, one for production reports and the other for alarm printing. The control stations utilize GE's 90-30 series programmable logic controllers (PLCs). Two control stations are used to acquire, process, and control the electrical equipment and process parameters during the inbound and outbound delivery processes. The main configuration of each control station consists of a CPU module (IC693CPU351), a bus interface module (IC693BEM331), an Ethernet module (IC693CMM321), I/O modules (IC693MDL645, IC693MDL940, IC693ALG223, IC693ALG392), and a power supply module (IC693PWR321). The industrial Ethernet supports standard TCP/IP and NetBEUI protocols, with communication rates ranging from 10 to 100 Mbps. The automation software for the operator station is Wonderware's InTouch 8.0, which contains a large number of graphical tools, allowing users to quickly and intuitively establish a real-time window for monitoring the process. Upgrading and maintenance are fast and convenient. It has online configuration, real-time and historical trends, data acquisition and processing, flexible user-defined reports, alarms and management, and an extensible configuration wizard. The operating system software is Microsoft Windows 2000, and the tool software is Microsoft Excel 2000. 4 System Function Design and Implementation 4.1 Delivery Process Setting The following delivery route settings are set: (1) Selection of warehouse for unloading and warehousing delivery system: According to the cement grade and production management needs, any one of the warehouses from 1# to 4# must be selected before the unloading and warehousing delivery system can be operated. (2) Selection of outbound delivery process route: The outbound delivery process of cement warehouses 1# to 4# can be selected from any 1 to 4 warehouses in the packaging warehouses 1# to 4#, or any 1 to 4 warehouses in the bulk warehouses 1# to 4#. Two warehouses and a shipping and delivery process. Several warehouses from 1 to 4 cement warehouses can be selected for simultaneous outbound shipments, but the selected delivery process for the packaging warehouse, bulk material warehouse, and shipping process must be unique. 4.2 Monitoring Function: Data Acquisition/Processing Function: The system acquires digital signals including manual/automatic signals from electrical equipment, running signals, various fault signals, power signals, equipment start/stop control signals, and process status signals; analog signals mainly include material level and current. Control Function: Implements three control modes: manual control, single-unit remote control, and automatic control. Manual control is used when the automatic system stops or malfunctions, when electrical equipment is maintained on-site, or when handling emergencies. Single-unit remote control, whose start/stop control does not affect the status of any other equipment, is mostly used for single-unit equipment operation, commissioning, maintenance, etc., meeting production and safety requirements, and is implemented at the operator station. Automatic control automatically starts/stops each electrical device according to process requirements, automatically starts/stops each warehousing system, delivery system, packaging system, etc., realizing sequential control, interlocking control, fault interlocking control, and process control. Operation Functions: Includes operation mode switching, operation selection, operator login, "permissions," and other routine operations. Monitoring Functions: The system is divided into twelve distribution process screens according to the process flow: 1#~4# inbound system, 1#~4# outbound distribution system, bulk material outbound system, packaging outbound system, and the overall distribution process. It displays and monitors the operating status of each process in real time through dynamic, color-changing, flashing, numerical, bar graph, and curve methods, providing a fully Chinese interface. It can also display the signal status of each device in split screens or pop-up windows; Figure 3 shows one of the system's process monitoring screens. [align=center] Figure 3 Process Monitoring Screen[/align] Trend Functions: Provides real-time/historical trend functions for process parameters such as material level in each warehouse and current of main equipment. Recording Functions: Records important electrical equipment start/stop, important operations, faults, emergency shutdowns, and parameter over-limits. Alarm Function: Provides alarms for various electrical equipment malfunctions, parameter over-limits, emergency shutdowns, system failures, and system software failures, with Chinese prompts and audible alarms. Historical Storage: Data trends, alarms, and records can be stored for up to three months. Reporting Function: Includes alarm reports, various production reports, trend records, historical record reports, etc., enabling scheduled, on-demand, and real-time printing. 4.3 Information Management: The operator station establishes a real-time database for real-time information such as on-site I/O signals and data. Based on this data, a historical database, alarm database, and safety information database are formed. The system's operation, monitoring, trends, records, alarms, historical storage, and reports are crucial information for port resource planning and management, and are an important basis for achieving information management. Using this data, communication with the management system via Ethernet enables the following ten management functions: Distribution Process Management: Management and priority management of twelve distribution processes, including the 1#~4# inbound system, the 1#~4# outbound distribution system, the bulk material outbound system, the packaging outbound system, and the overall distribution process. Equipment Maintenance Management: Includes electrical equipment and instruments in each distribution process. Bag Management: Count of valid bags and damaged bags. Scheduling Management: Coordination of unloading, bulk material loading and unloading, and packaged material unloading. Decision Management: Decision-making management based on production, market, inventory, loading volume, and shipping volume. Statistical Management: Management of logistics and distribution statistics, including inventory and turnover rates. Market Information Management: Comprehensive market information to guide production across the plant. Business Billing Management: Billing management based on bagged material loading documents, bulk material loading documents, and bag management. Vessel Operation Management: Vessel operation management for unloading and loading vessels based on port terminal characteristics. Vehicle Management: Management of vehicle entry and exit, utilizing electronic barcode technology. These management functions are integrated with a business office system to achieve various management functions including logistics management, human resource management, port area management, and e-commerce platform management. The InTouch configuration software was used to develop alarm processing and storage, data calculation and processing, database redundancy control, I/O data connection, and graphical interface. The system collects more than 2,000 digital and analog data points, and the real-time database contains more than 5,000 data points. Information management is implemented based on Microsoft SQL database. 5. Conclusion Utilizing PLC control technology and network technology is a fundamental measure to achieve automation and informatization of modern port logistics distribution. It allows for timely monitoring and understanding of the operating conditions and process parameter changes of various equipment in the distribution process, optimizing the distribution process, ensuring stable and safe operation, reducing distribution costs, improving management level, and ensuring long-term normal and stable operation to achieve optimal benefits. It accurately transports materials from one location to another with the best path and fastest speed, completing the spatial and temporal transfer of materials to ensure the high-efficiency operation of the port. Since its implementation, this system has been safe and stable, achieving significant economic benefits. The innovations of this paper include: the ability to arbitrarily set the distribution process through the operating interface as needed, combining management and control functions; achieving information management while realizing process control, realizing substantial integrated control and management; and integrating industrial Ethernet with Genius. The combination of I/O buses enables the rational configuration of the control network. References : 1. Wang Xianglin. Networking Technology and Configuration [M]. Beijing: Tsinghua University Press, October 2003. 2. He Yanqing. Principles and Applications of Distributed Control Systems [M]. Beijing: Chemical Industry Press, 2002. 3. Gao Suping. Development and Implementation of Industrial Control Network Architecture. Microcomputer Information [J], 2005, 6: