Abstract : In the tomato sauce sterilization temperature monitoring system, a Siemens S7-300 PLC was used as the hardware platform, and STEP7 and WinCC6.0 were used as the development environment to realize real-time data acquisition, display, and alarm functions. The system has a user-friendly graphical interface and is easy to operate. Keywords : Tomato sauce, sterilization tube, Siemens S7-300, WinCC [align=center]Design of the sterilization section control system for Tomato sauce He Ping, Lou Yi, Xie Lirong (College of Electrical Engineering; Xinjiang University; Urumqi, Xinjiang 830008)[/align] Abstract : In this paper, a sterilization section control system was designed. Sterilization is a section of the tomato sauce product line. Using the programmable logic controller Siemens S7-300 as a hardware development platform and Siemens software STEP7 & WinCC6.0 as a software development environment, it realizes functions such as data collection, display, and real-time alarming. The system has characteristics such as a friendly interface and easy operation. Keywords : Tomato sauce, section sterilization, Siemens S7-300, WinCC 1 Introduction The tomato industry is one of the three pillar industries of Xinjiang, namely, "black, white, and red" (referring to the three major agricultural products). As Asia's largest tomato paste processing area, Xinjiang has formed a cluster of tomato paste processing and export enterprises, with an annual tomato processing capacity of 800,000 tons, accounting for approximately 90% of the national tomato processing volume. Research on tomato paste processing control systems can apply control technologies with independent intellectual property rights to production, reducing reliance on foreign technologies, thereby lowering the technical costs of tomato paste production and enhancing the competitiveness of China's tomato paste industry in the world. 2. Shell-and-tube Sterilization Process Shell-and-tube sterilization is one of the key stages in tomato paste processing. A shell-and-tube system consists of several layers of interlocking pipes, with larger pipes inside smaller ones. The material and sterilizing water can fully contact each other within the pipes. The rotating and tumbling paste in the pipes exchanges heat with the superheated water in the inner and outer jackets to achieve sterilization. This paper uses a five-layer shell-and-tube system, with three layers of water and two layers of material, greatly improving sterilization efficiency. The shell-and-tube system is divided into three sections: sterilization, cooling, and heat preservation. In the sterilization section, the temperature of the material is rapidly raised to the specified temperature to kill various molds. The cooling section rapidly cools the sterilized material to maintain its freshness and color. The heat preservation section maintains the material temperature, preparing it for filling. The sterilization section is the key part of the entire production line; the quality of sterilization directly affects the product quality. If the sterilization temperature is insufficient, the product will spoil due to the presence of mold; if the sterilization temperature is too high, the freshness and color of the product will decrease excessively, ultimately affecting the product quality. The tube sterilization process flow is shown in Figure 1. [align=center]Figure 1 Sterilization Process Flow Diagram[/align] The main parameters of the sterilization section are shown in Table 1. [align=center]Table 1 Main Parameters of the Sterilization Section[/align] 3 Lower-level Computer Programming The most important control parameter of the tube sterilization section is the sterilization temperature. In the actual production line, the sterilization temperature must be precisely controlled to stabilize it at 106℃, with an allowable variation range of 102℃-110℃. The sterilization temperature is determined by the superheated water temperature, which is determined by the steam volume. The steam pressure is stable; the sterilization temperature can be controlled by adjusting the opening of the steam valve. This control method is used in the production site, and the sterilization temperature control block diagram is shown in Figure 2. [align=center]Figure 2 Sterilization Temperature Control Block Diagram[/align] Based on the field control object and control equipment, the PID control module SFC41 integrated in STEP7 is called, and closed-loop control is adopted to complete the design and programming of the controller, as shown in Figure 3. [align=center]Figure 3 Controller Design Process[/align] The sterilization temperature is controlled by PID. The temperature value is stored in MD104 as the input value of the PID control module, and its output value is stored in MD100. At the same time, the output of the PID control module MD100 is used as the set value of the controller, and the control quantity of the controller is the temperature input value. The adjusted value is returned to MD104 as the input value of the PID control module for cyclic adjustment. In addition to the precise control of the sterilization temperature, the start and stop of various pumps and valves also need to be controlled. The pumps that need to be controlled are the feed pump, discharge pump, cooling pump, water pump, discharge valve, and circulation valve. This can be achieved by writing a basic start-stop ladder diagram in STEP7. The block diagram of the discharge valve/circulation valve control program is shown in Figure 4. [align=center]Figure 4 Control Block Diagram of Discharge Valve/Circulation Valve[/align] 4 Development of Upper Computer Monitoring Screen Enter the WinCC editing interface, create a new S7 external variable driver program, and create a connection under the corresponding communication method according to the design requirements. Create the required variables in the connection and map the variables to the channels one by one. Create 28 external variables, as shown in Figure 5. [align=center]Figure 5 Variable Table[/align] Create online curves and online data archiving to display the changing trends of sterilization temperature, cooling temperature, and heat preservation temperature, and save the real-time data archive. Simulate the online curve using the variable simulator included with WinCC, as shown in Figure 6. [align=center]Figure 6 Online Curve[/align] Select WinCC Online Table Control in the Object Palette to create an online archiving table, as shown in Figure 8. [align=center]Figure 8 Online Archived Data[/align] Creating an Alarm Log: Open the alarm log, select "Message Block," right-click and select Configure Message Block. In the pop-up page, add a system block, selecting the duration, date, time, status, and number; add a user text block, selecting the message text and error point. Create a graphical screen. Name it "Alarm." In the object palette, select WinCC Alarm Control, right-click and add. An alarm log table will be automatically added to the graphical screen as shown in Figure 9. [align=center]Figure 9 Alarm Log Table[/align] 5 Communication The S7-300's communication network includes: Data communication via Multipoint Interface (MPI) protocol: The S7-300 CPU integrates the MPI communication protocol. The physical layer of MPI is RS-485, with a maximum transmission rate of 12 Mbit/s. The PLC can simultaneously connect to a programmer, computer, HMI, and other SIMATIC PLCs via MPI. PROFIBUS: Includes PROFIBUS FMS, PROFIBUS DP, and PROFIBUS PA buses, with RS-485 as its physical layer. Industrial Ethernet: Generally used for upper-level networks. Point-to-Point (PtP): Connects two back-end S7 PLCs and non-Siemens devices such as computers, printers, and scanners. AS-i (Actuator-Sensor-Interface): The actuator-sensor interface, located at the lowest level of the control system, used to connect field binary devices. Both lower-level computer program uploads and upper-level computer monitoring use TCP/IP communication protocol to communicate with the PLC. The PLC and each computer form a network through a switch, and the CPUs communicate with each other via Ethernet. I/O devices and the PLC communicate using traditional signal methods; analog signals use 4-20mA and 1-5V standard signals, and digital signals use DC24V signals. 6. Conclusion The tomato sauce processing tubing sterilization section control system includes detection, control, communication, monitoring, control algorithm implementation, and software development. This system employs advanced control methods such as host computer monitoring, host computer-slave computer communication, and PLC Ethernet communication. The system can be configured and monitored via a host PC, meeting the requirements of centralized control and decentralized hazard management. References [1] Tomato sauce processing data. Tunhe Group Changtong Tomato Sauce Products Branch, 2000. [2] Yao Yi. Analysis and control of factors affecting the viscosity and color difference of tomato sauce [J]. Shihezi Science and Technology, 2006, No. 4, 33-34. [3] Cui Xiaoling, Mao Min, Zhang Wenjie, Liu Le, Shen Guangjun, Tan Hua. Application of HACCP system in tomato sauce production and quality control [J]. Xinjiang Agricultural Sciences, 2004, No. 41, 101-102. [4] Liao Changchu. PLC programming and application. First edition. Beijing: Machinery Industry Press, 2002. About the author: He Ping (1957-) female, experimentalist, engaged in laboratory teaching and research, [email protected], 13909918506; Lou Yi (1958-), male, senior experimentalist, engaged in laboratory teaching and research, [email protected], 13579215632; Xie Lirong (1964-), female, lecturer, engaged in teaching and research in control theory and systems, [email protected], 13579823332. Mailing address: School of Electrical Engineering, Xinjiang University (North Campus), Xie Lirong, 830008.