Abstract: Industrial automation is developing towards comprehensive enterprise automation and integrated management and control. How to fully utilize information integration technology and real-time control technology to maximize the role of equipment resources is key to safety, high quality, low cost, and high profit. The main research work of this paper is to develop an open fiberglass logistics line control system based on OPC technology. Keywords: Industrial control, OPC, Fieldbus 1 Introduction Driven by the rapid development of computer network technology, industrial automation systems are gradually transitioning from centralized to distributed systems. In distributed systems with multiple servers and workstations, data communication is usually formed through a local area network. Therefore, adding servers or workstations as new nodes to access the network can improve and enhance system functionality. OPC technology is the latest development in object-oriented technology. Applying it to the design of FCS systems can realize open FCS systems. FCS systems are important process control systems, and achieving openness and interoperability of FCS systems is the development direction of industrial automation software. Using the VB high-level programming language, Siemens' powerful programming configuration software STEP 7, and SIMATIC NET software, a fiberglass logistics line control system based on OPC technology was developed. 2. Application of PROFIBUS Bus Compared with other fieldbus technologies, PROFIBUS fieldbus technology has its own unique advantages. To reduce system costs and simplify implementation for practical industrial applications, PROFIBUS-DP divides its system stations into three types: Type I DP Master (DPM 1), Type II DP Master (DPM 2), and DP Slave. Of course, these three types of stations are only divided according to logical functions; in reality, a single physical device can simultaneously perform all three functions, acting as both a master and a slave. PROFIBUS-DP provides the following basic service functions: 1. Reading master station diagnostic information. 2. Uploading and downloading parameters. 3. Activating bus parameters. 4. Reading slave station diagnostic information. 5. I/O data interaction. 6. Setting slave station parameters. 7. Verifying slave station configuration information. 8. Issuing control commands to slave stations. 9. Reading slave station configuration data. 10. Reading slave station I/O data. 11. Setting slave station address data. PROFIBUS-DP employs two transmission technologies: RS485 and fiber optic. Its data transmission rate is adjustable, meeting both low-speed and high-speed requirements, with a maximum rate of 12Mbps, higher than other major fieldbuses. RS485 is a mature and inexpensive data transmission technology. It uses twisted-pair cable as the transmission medium, and its transmission distance is related to the transmission rate. In applications involving long-distance transmission or severe electromagnetic interference, fiber optic transmission technology can be used. Repeaters can extend the bus segment range, and fiber optic connection modules can form a hybrid cable and fiber optic network. Simultaneously, these network connection modules are used. 3. Overall Control System Structure Design 3.1 System Overview A logistics system refers to a whole that transports accurate materials to accurate locations at accurate times and with accurate quality requirements. Therefore, logistics systems have strong temporal and spatial characteristics, technical aspects, and economic considerations, and are important factors influencing the production and operation of modern enterprises. According to the planning and design, the entire fiberglass logistics transmission system is divided into five working units: the drawing and feeding unit, the drying furnace distribution unit, the three-dimensional storage unit, the outbound winding area distribution unit, and the empty car handling unit. The system's control software is responsible for the automatic and semi-automatic continuous conveying control from fiberglass filaments to fiberglass products, and for resolving issues related to classified storage and on-demand allocation. It also needs to provide real-time control, display, and alarm information regarding the production line's operation. The entire logistics line requires a high conveying capacity. To ensure this high capacity, in addition to low failure rates of the conveying equipment, a high-performance, stable, and reliable automated control system is needed to control and manage the entire logistics process. Based on system requirements and practical application experience, the technical solution for the automated control system of the fiberglass logistics line adopts a distributed control system composed of Siemens PLC automation products to achieve a high level of automated control and management, thereby achieving the goals of low energy consumption and reliable, stable operation. The system configuration fully considers the scalability of the system's software and hardware resources, allowing for future expansion and upgrades without affecting the operation of existing equipment. 3.2 Logistics Line Workflow The entire automated logistics transmission line consists of five working units: the drawing and feeding unit, the drying oven distribution unit, the three-dimensional storage unit, the outbound winding area distribution unit, and the empty car handling unit. Its workflow is shown in Figure 1: [align=center] Figure 1 System Workflow[/align] 3.3 System Composition The system mainly consists of an Advantech host computer, a Siemens S7-400 workstation, an S7-300 intelligent slave station, and a CP5611 data acquisition card, as shown in Figure 2. [align=center] Figure 2 Control System Structure Diagram[/align] The entire control system is based on the Profibus-DP fieldbus mode: Structurally, the computer control system is abstracted into a three-layer model consisting of a basic equipment layer, a process control layer, and a host information management layer; the basic equipment layer includes the control PLCs for the robotic arm, the accumulation conveyor line, and the automated warehouse, the ID identification device for the trolley, and a large number of sensor devices; the process control layer uses a Siemens 57-400 PLC, connected to a Profibus-DP network, and connects the bus instrumentation and control equipment to the host computer through a DP/PA connector, integrating real-time general data to the host computer's server. The upper-level information management layer integrates control processes, information management, and communication networks to achieve data sharing. Relevant personnel can log into the upper-level server and control the operation of equipment on the production site according to their respective permissions, truly achieving the goal of centralized management and decentralized control. Basic Equipment Layer: Field devices are connected to the fieldbus network as network nodes, and the control of the production process is completed by fieldbus devices with function blocks. As the number of field devices used in the system increases and their functions are continuously enhanced, the field data that the equipment layer can provide also increases. Transitional Control Layer: Used to monitor and control the system usage of the production process, transmitting the collected field data to the information management layer. The transitional control layer cooperates with and coordinates the work of various field devices, providing a supporting environment for advanced control and process operation optimization, enabling the system to have a higher level of control and a higher management level. The upper-level application not only participates in and controls every step of the communication between field devices, but also needs to coordinate and manage the communication processes of other field devices in the system, detecting and eliminating conflicts between multiple communication processes. 3.4 System Functional Design In this computer control system, the upper-level management function block accesses field devices to obtain field data through the communication function block, thus tightly integrating the upper-level control and information management with the communication of the lower-level field devices, as shown in Figure 3. [align=center] Figure 3 Communication Diagram[/align] An independent field communication function block is used, enabling the upper-level management function block to send data requests to the field communication function block to obtain the required field data; the field communication function block receives the request, completes the field data acquisition task, and sends the field data back to the management function block. In this way, the communication tasks of the field devices are completed by a dedicated device communication program, and the system's management layer does not directly access the underlying hardware devices. Therefore, for the upper-level management function block, there are no longer any field device compatibility issues, and changes in the communication protocols and methods of the underlying field devices, or even updates to the underlying field devices and changes in the network structure, will not affect the management function block. From the three-tiered model of the computer control system—basic equipment layer, process control layer, and upper-level information and management layer—it can be seen that there are two main communication processes in the communication function block: communication between the device layer and the data layer, and communication between the data layer and the application layer. These two communication processes are closely related yet independent. The main task of communication between the device layer and the data layer is to collect data from field devices and control and manage them. When the communication function block completes the communication function between this layer, its implementation method is closely related to the communication method of the field devices and communication devices, as well as the network topology. The main task of communication between the data layer and the application layer is to complete the processing and manipulation of data, provide a unified data platform to the management program, and realize data transfer and sharing between application programs. The development of the communication function block at this layer needs to comprehensively consider the programming technology, operating system, database, and other aspects adopted by the system. 3.5 Openness of Communication Function Blocks In many computer control systems, field devices are frequently updated and upgraded, and system functions and tasks change significantly. Therefore, maintaining the openness and modular architecture of the communication function block is a basic requirement for its development. The openness of the communication function block is reflected in: 1. The communication function block should be as unaffected as possible by changes in system hardware. 2. Each module within the communication function block should be independent of the others. 3. The communication function block should be independent of the upper-level management module. However, in the actual development of the communication function block, the implementation of many functions of the communication module can be based on the specific hardware environment and application requirements of the system. It is not required that the developed communication function block be open and universally applicable to all systems and meet all system needs. This allows for the omission of some functions in the communication function block that are not needed by the user. This simplifies the software structure, makes development easier and faster, and can meet specific and special user requirements. 4. Functional Analysis of the Central Control System The central control system, as the decision-making and management body of the entire automated control system, directly affects the reliable operation of the logistics automated control system due to factors such as the rationality, reliability, and intuitiveness of its configuration. This system mainly includes two parts: the control workstation and the data server. As the data storage component of the logistics line control system, the database's performance directly affects the performance of the entire control system. When designing the database for the logistics line control system, we mainly consider the following aspects to meet the data storage and retrieval requirements of the logistics line control: 1. Meeting data storage requirements. 2. Ensuring data accessibility for end users. 3. Possesses a robust database security mechanism. 4. The overall database performance is reasonable. 5. Stores as little redundant data as possible. Author's Innovation This paper first elaborates on the entire workflow of the fiberglass logistics conveyor line. Based on this, it proposes a framework structure for an open fiberglass logistics line control system based on OPC technology. Functionally, it integrates control and management. Technically, it designs a communication module based on OPC technology and elaborates on the reasons for adopting this communication module and its superior performance. This paper also specifically analyzes the application of the PRFIBUS-DP fieldbus, verifying its excellent performance in practice. Finally, the functions of the entire control system are described in detail. References: [1] Gao Jianping, Real-time Data Management System for Power Plant Based on OPC Technology [J], Industrial Control Computer, 2002 (5): 67-69 [2] S. Vitturi. On the use of Ethernet at low level of factory communication systems [M]. 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