Abstract: This paper introduces an advanced control system based on fieldbus technology; discusses the selection of a visual monitoring communication network scheme; and introduces the configuration of a redundant visual monitoring system based on fieldbus. Keywords: Fieldbus; FCS; PLC; Visual monitoring; Redundancy 1 Introduction The development of computer digital communication technology and information technology has promoted the progress of automation technology, especially the fieldbus technology that has emerged in the last decade. Its development has prompted a major change in the structure of automation systems. The application of fieldbus control systems (FCS) is becoming increasingly common and is developing towards intelligence, networking, and integrated monitoring and management. Computer visual monitoring appeared abroad in the 1980s. Due to technical and economic reasons, it was not applied in China until the mid-to-late 1990s. The functions have evolved from simple to complex; in terms of monitoring scope, it has expanded from the initial single machine to production lines and even the entire industry; in terms of the network system structure of monitoring, it has developed from the initial master-slave to master-multiple slave and multi-master-multiple slave; the hardware has developed from the initial closed self-design to the adoption of open, standardized system integration schemes or commercial products. Before the application of computer visualization monitoring technology, a dedicated manual operation console and production process control simulation screen are usually used. Many master control electrical appliances, indicator lights and display instruments are arranged on it. There is also a corresponding process flow at the simulation screen. This monitoring method is essentially a "hardware wiring logic" and will inevitably be replaced by a new monitoring method. 2 Visual monitoring communication network scheme 2.1 Visual monitoring communication network based on "simple protocol" The "simple" of the communication protocol mentioned here is relative to the OSI/RM model. In Figure 1, one IPC monitors one PLC[1]. On the IPC side, the Mscomm control in VB is used to complete the reading and writing of its serial port. VB program Mscomm.setting="9600,N,8,1". This communication can adapt to the communication requirements of a single master station - a single slave station and can achieve a relatively simple function. If the situation is complex, it has greater limitations. For example, when a PLC is added to RS485, all PLCs are communication slave stations and IPC is the master station. When the hardware and software of IPC have problems, monitoring cannot be carried out. 2.2 Fieldbus-Based Visual Monitoring Communication Network Fieldbus technology's communication protocol is based on the OSI/RM model and aims for open interconnection. Fieldbus, through multi-layered protocols, can address issues such as bus control, collision detection, and link protection. Communication can be seamless, with no "master"/slave distinction or multiple master stations, providing a basis for redundancy. Therefore, only a fieldbus-based visual monitoring communication network can achieve redundancy. The redundancy of visual monitoring is built on the PROFIBUS fieldbus. PROFIBUS uses a hybrid media access method at the data link layer in its bus access protocol. To ensure reliable operation of the visual monitoring system, the redundant monitoring system should also adopt a hybrid approach. 3. Composition of the Visual Monitoring Redundancy System This paper discusses the design of a visual monitoring redundancy system using the 480-ton refined rice production automatic control system project undertaken by our university for Hunan Jinjian Rice Industry Co., Ltd. The production process flow diagram of Jinjian Rice Industry Co., Ltd. is shown in Figure 2. As shown in Figure 2, apart from the initial cleaning and finishing sections being common sections, the main production sections consist of two production lines. The characteristics of the I/O signals in this system are: numerous points (approximately 2000 points) and wide distribution. The control characteristics of this system are: long process flow, many changes, complex and variable interlocking relationships, material flow delays, and a combination of batch and continuous processes, etc. Based on the process control tasks and requirements and the characteristics of the control system, a fieldbus control system (FCS) is constructed as shown in Figure 3. [align=center] [/align] 3.1 Hardware Aspect In Figure 3, PLC1 mainly controls the common initial cleaning and finishing sections; PLC2 and PLC3 control the first and second production lines respectively (rice hulling, rice milling, and sorting and packaging sections). Each PLC also has several I/O remote control stations. IPC1 is the operator station, mainly responsible for monitoring; IPC2 is the engineer station, which, in addition to PLC programming, network configuration, and monitoring configuration, also serves as a backup for IPC1 monitoring. The PLC uses the German Siemens S7-200 (CPU315-2DP) model; the IPC uses the Taiwan Advantech industrial control computer (P2 model), equipped with a 19″ display, UPS, printer, etc. 3.2 Communication Network and Interface The communication network uses the PROFUBUS fieldbus, which was jointly proposed by 13 companies including SIEMENS and 5 research institutions, and is now widely used. Each PLC is connected to the PROFIBUS fieldbus through the Siemens CP341[2] communication module. The IPC is connected through the Siemens CP5412A communication adapter card. As shown in Figures 4 and 5. [align=center] [/align] 3.3 Software The software uses Siemens Wincc[3] visual monitoring configuration software. It is based on the 32-bit Windows 95/98/2000 standard operating system. It has a graphic designer, alarm processor, report editor, variable manager, etc. WinCC software enables powerful computer-based visual monitoring of rice production. The system is divided into 10 main monitoring screens and several production data report screens, categorized by production process. These screens can be switched at any time. Operators can select the operating mode for each section on the monitoring station. In automatic control mode, each section starts and stops automatically; in manual mode, operators can directly control each device from the monitoring station. Regarding fault alarms, while the system automatically handles faults, in addition to system audible and visual alarms and corresponding screen color changes or flashing, relevant information tables are immediately generated. Redundancy in the visual monitoring software is reflected in the "redundancy" function of the WinCC configuration software. This function allows two parallel WinCC monitoring stations to run simultaneously, ensuring monitoring continuity. In Figure 3, if IPC1 fails, IPC2 can take over monitoring. When IPC1 resumes operation, all data secretly collected by IPC2 during the period when IPC1 was not running will be automatically transferred to IPC1, thus allowing both WinCC monitoring stations to run simultaneously again. Characteristics of Redundant Visual Monitoring Systems Compared with traditional control methods, the author believes that it has at least the following three characteristics: 1) It makes the control and management process of production visible and scientific. Graphics and images on the computer screen, as well as keyboards and mice, are all means of human-machine information interaction. 2) It has complete functions. The biggest feature of current computer visual monitoring technology is real-time multitasking, that is, multiple tasks such as data acquisition and output, data processing and algorithm implementation, graphic display and human-machine dialogue, real-time data storage and retrieval, and real-time communication are performed simultaneously on the same computer. 3) It is reliable in operation. After a large number of switches, indicator lights, instrument consoles and analog screens are replaced, the hardware and wiring are greatly reduced, significantly reducing the probability of monitoring anomalies caused by hardware failures; in addition, if an industrial fieldbus environment is adopted, multiple monitoring master stations can be set up to form a redundant monitoring system. The monitoring master stations can serve as backups for each other, which effectively improves the reliability of operation. 5 Conclusion The redundant visual monitoring system based on PROFIBUS fieldbus has been running stably for two years. Operational practice shows that setting redundancy is an effective way to improve the reliability of visual monitoring, and the use of fieldbus provides a basis for setting redundancy. References: [1] Siemens (China) Co., Ltd. SIMATIC S7-200 Programmable Controller CPU22X System Manual [Z]. Beijing: Siemens (China) Co., Ltd., 2001. [2] SIMENS, SIMATIC Manual, Point-to-point connection CP 341 instation and Parameter Assignment [M]. SIMENS AG, 1998. [3] Siemens (China) Co., Ltd. Wincc V4.02 Configuration Manual [Z]. Beijing: Siemens (China) Co., Ltd., 2000.