Abstract: The transformation project of automatic control system of Beijing surface water plant adopts Rockwell Automation's ControlLogix and CompactLogix. The communication in the plant area uses ControlNet redundant network and the remote communication adopts wireless mode. The data compatibility between the new and old systems was designed and implemented during the transformation. In the process of controlling process migration, PLC program optimization and process improvement were completed. Keywords: network planning data compatible program optimization process improvement 1 Introduction The surface water plant of the Beijing Municipal Water Supply Corporation is a highly automated surface water plant that was completed and put into operation in 2000. The water plant is designed to produce 300,000 tons of water every day. The technology and technology are all imported from abroad, and the self-control system that has been in operation for ten years is facing difficulties. Based on its decade-long operational experience, the Beijing Municipal Water Supply Company is determined to rely on its own technological capabilities to transform the water plant automation control system through independent research and development. In 2009, the PLC automatic control system of the whole plant was completely transformed. In order to not affect the normal operation of the entire water supply production, the renovation project was carried out in two phases, and by March 2010, the renovation project was completed. The reformed automatic control system meets the requirements of the eight water plant production, further improving the performance of the original system, and achieving a number of technological breakthroughs and process improvements. The new system pioneered a number of technological innovations that clearly exceeded the design level of the original system and the legacy problems of the original system were properly addressed. Pump room to achieve frequency control, constant pressure water supply, to achieve a good energy-saving effect; successful realization of the PLC automatic control system and third-party equipment, communications, laid the foundation for the success of the project; for the water into the factory, precipitation, filtration The status quo of equipment and technology, to achieve a number of process reforms and innovations; in the transformation process, the software compatibility of the new and old systems is successfully debugged, saving the company a large amount of hardware-compatible costs. 2 Control Network Optimization 2.1 The topology of the original automatic control system The surface water plant original automatic control system uses Square D PLC as the main equipment of the automatic control system. Logically, there are 7 master stations and 9 substations. The PLC of the company's dispatch center has been dismantled, and the wireless communication between the PLC of the Huangshuizhuang Water Management Station and the plant has been interrupted due to equipment. Substations use small SY/MAX 50 series PLCs and other stations use medium-sized SY/MAX 400 series PLCs. The PLC in the factory uses the twisted-pair wires and the optical fiber to form the SY/NET industrial control network according to the product requirements of Square D (excluding the PLC in the dehydration room). The central control room exchanges data with the PLC of the Huangshuangzhuang water intake using 400 MHz wireless communication. The SY/NET network communication rate is 2M, and the wireless communication rate is 9600 bps. Square D PLC uses the HDLC protocol, which is relatively simple but efficient. The system topology is shown in Figure 1. The topological diagram of the original automatic control system of the water plant 2.2 Network Planning for a New Automatic Control System In the entire network system, we use the Netlinx structure of Rockwell Automation. In this network architecture, the CIP protocol is adopted. Based on Producer/Consumer communication, it is no longer the former master-slave mode. In this way, the CPU is no longer a bottleneck, which reduces the burden on the CPU and enables I/O sharing. The data exchange between the units can be performed directly through I/O without the need to exchange them through the CPU. In this way, the data exchange speed between the units can basically reach the real-time level. The control level adopts the new network mode of ControlNet. Dual-media redundancy is used between networks to ensure the stability of the system. In this PRODUCER/CONSUMER mode, it does not require a separate source/destination address, instead of a data identifier, so different consumers (information receivers) can receive from the producer simultaneously according to the data identifier ( (Information producer) information, if some information is what it does not need, it can be ignored, and only deal with the information it needs. This brand-new network model is a revolution of the traditional network model, it greatly Improve network efficiency. This model is also used by DEVICENET and FOUNDATION FIELDBUS, which represents the trend of next-generation networks. The system monitoring mainly adopts AB company's ControlLogix system, and the communication function is designed in the whole system. The ControlLogix architecture can use a unique ControlBus backplane to create a communications gateway for the entire system. The ControlBus backplane does not use the typical master-slave mode, but another approach, which is based on the producer/consumer, in the CONTROLNET and DEVICENET communications networks. You will encounter this pattern. For some small stations, AB’s CompactLogix system is used. CompactLogix also has a human-machine interface system on the control station. It uses AB’s PanelView operator interface to provide rich functions, including advanced alarm processing and screen security settings. , Analog dial, memory card compatibility, online printing, etc. These functions will provide operators with more intuitive operation methods. Different control systems, the same programming configuration environment, and a unified network system, this design saves a lot of training costs and project execution time. According to the water plant's production process and management requirements, the original system's site structure was used as the basis for the system design, and the original six main stations and nine substations were retained. Six master stations use Contrologix series PLCs; nine substations use Compactlogix series PLCs, and eight substations of the filter station control the action of 16 filter pools. The belt filter presses in the dehydration room are also dominated by a sub PLC. Dehydration between the PLC, 8 filter sub-station PLC uses Compactlogix series PLC, other stations use Contrologix series PLC. The ControlNet redundant network is adopted between the main network of the plant, ie the PLCs of the main stations, and between the master station and the substations. If communication network A fails, the network can be changed to the B network without manual setting. In order to ensure the stability of the signal and the immunity of the medium, the optical fiber is selected as the network medium in the section accompanied by high voltage and high current. The central control room and Huangshuangzhuang Water Intake Management Station PLC and Gangnan Water Intake Management Station RTU communicate wireless data through a third-party communication module MVI56-MCM. The host computer and touch screen are all hung on the ControlNET redundant network. ControlNET network communication speed is 5M/s, wireless communication speed is 19200bps. 3 data compatible with automatic control system 3.1 Data Compatible Design Background Since the transformation of the automatic control system of the surface plant can not affect the normal operation of the entire water supply production, the reconstruction work should be implemented in a step-by-step manner. This staged transformation will inevitably lead to the long-term coexistence of the new system with the original system. Then, the interconnection of the two systems is a difficult point in the project. System compatibility refers to the interconnection and intercommunication between the new automatic control system and the original automatic control system. The new automatic control system will write the data of the reconstructed site into the original automatic control system according to the data requirements of the original automatic control system, so as to ensure the complete display of the original automatic control system. . However, the original automatic control system cannot send instructions to the equipment of the new automatic control system. The compatibility of the new system with the original system can be solved in two directions: hardware compatibility and software compatibility. Both compatible methods have their advantages and disadvantages. From the perspective of investment protection, software-compatible solutions are more feasible solutions. 3.2 Hardware Compatibility Hardware compatibility refers to the two-way conversion of two different PLC protocols by adding hardware adapters between the new system and the original system, so as to achieve interconnection and intercommunication between the two systems. The typical application of this method is the filter renovation project of Yangzhou No. 4 Water Plant. The system topology of this transformation method is shown in Figure 2: Figure 2 Hardware Compatible System Structure This method of handling compatibility can be relatively smooth transition from the original system to the new system, more suitable for longer-term renovation projects. Of course, it also has certain drawbacks. First, the selected hardware adapter is a transitional investment. This device loses its significance after the new system is built. In general, dedicated protocol conversion adapters are often used at a high price because of their single use, and expensive investments may only be used. One or two years, it is not worthwhile considering from hardware cost; In addition, this kind of transformation method can't save the cost of software development. All the lower-level programs and higher-level software in the original system need to be rewritten and re-developed. Also, the hardware is used. Compatible from the point of view of transformation will limit the range of equipment selection for the new system, so that the transformation work in a sense becomes an advanced upgrade to an outdated product. Hardware-compatible system transformation diagram shown in Figure 3 Figure 3 Hardware-compatible system transformation 3.3 Software Compatibility Software compatibility refers to the consideration of the interconnection and intercommunication between the new system and the original system from the upper software. In general, IPC upper configuration software supports multiple PLC protocols. The purpose of doing so is to enable the software to support more manufacturers of PLC products, thereby maximizing the applicability of its products. So we can let the configuration software to complete the data exchange between the two systems. The configuration software reads data from the new system and writes it into the original system. It can maintain the original system's logical integrity in the transitional stage. On the other hand, the new system reads data from the original system to complete the new system's control strategy and test the new system's Comprehensive performance. This kind of compatibility solution can reduce engineering investment on the one hand, and it will not increase the workload of programming too much on the other hand. Of course, this method is not perfect. The compatibility of the system is maintained by the survival of the configuration software in the system. If the host computer goes down or goes out of operation, the interworking chain of the two systems will be interrupted. This requires that the development of the upper software must be ahead of the hardware installation and commissioning. At the very least, it must be completed at the same time. Moreover, the upper program must be fully tested in the laboratory. Make sure to perform as few modifications as possible after the program is installed. Of course, there are similar problems in hardware-compatible solutions. After all, technological transformation projects are the primary conditions to minimize the impact on normal production. The compatibility of new and old automatic control systems will be implemented using OPC. The specific approach is to use the upper computer of a new system in the central control room as the OPC server that runs the Kepware for Square D service. The server of Kepware for Square D exchanges data with the upper software (RsView SE) of the new system, and the client is connected to the PLC of the original automatic control system. Using Kepware for Square D as a data exchange bridge between the new system and the old system. Site data that has been incorporated into the new system will be directly written to the PLC5 CPU in the original system by the upper software in an OPC manner. The OPC server is connected to the RS232 port of PLC5 through the serial port. Since Kepware for Square D does not support communication with the SY/LINK card, it is necessary to additionally add a program for writing data of the new system to the SY/LINK card mailbox in the PLC5 program. In this way, the data in the new system can be transmitted and displayed in the original system. The system topology of the software compatible solution is shown in Figure 4. Figure 4 Software Compatibility System Block Diagram 4 Surface Water Plant Process Improvement 4.1 Control Strategy Migration The transplantation of control strategies is actually the migration of various control process programs running in the PLC of the old system to a new PLC program. In general, this work is theoretically simple. It just reads the old program and rewrites the program according to the programming constraints of the new device, so that the two self-controlled devices keep the same behavior under the same incentive. However, in actual operation, this part of the work is the most tedious and most vulnerable to security risks. First of all, the two types of control devices must have differences in the programming rules and means of implementation. The programmer must be familiar with the characteristics of the two devices, and it is impossible to complete the task by simply copying the simple machines. In addition, the original system's control program is a crystallization of the complex conditions of the scene test, combined with the system maintenance personnel over the years to work hard to sum up the strategy of crystallization. The new system cannot have enough time to sharpen and field test. Most of the program modifications and on-site simulations must be completed in the laboratory. This will inevitably lead to deviations and omissions to some extent. Strive to minimize the possibility of hidden dangers. This part of the work is the key factor in determining the success or failure of the new system. 4.2 Program Optimization and Process Improvement In the PLC program design, the programmer should not stick to the original program, according to the current situation of equipment and technology, to achieve all the performance of the original system in a new way, and carry out improvement and innovation. After entering the factory water, the surface water plant settles through sedimentation tanks and filters through 16 filter tanks. The filter tank is an important part of surface water treatment and directly affects the quality of water. Programmers dare to innovate in program design and realize many improvements in the filter backwash process. First of all, the unreasonable abnormal alarm of the filter liquid level was eliminated and the loopholes in the original system program design were made up. When the filter is normally filtered, the liquid level is controlled at 0.95m, and high and low level alarms are provided. When the filter backwashing liquid level is only about 0.25m, lower than the normal filtration level. When the original program is backwashed, an unreasonable low level alarm will occur. The new system has been carefully designed by the programmer to overcome this drawback. Secondly, the filter backwashing process was improved, saving water and making the process more reasonable. When the original system filter tank is backwashed, the water extraction board gate is closed and the water extraction board gate is opened at the same time. At this point, the liquid level is still high, and a large amount of water in the filter tank is discharged to the sludge treatment system. In the period of manganese removal, the sludge treatment system is deactivated and is directly treated as sewage. The programmers and craftsmen work closely together and boldly improve. When the backwash is started, close the water intake plate gate, fully open the water outlet valve, and delay for 2 minutes so that the water in the filter tank continues to be normally filtered to the clear water tank. When the liquid level drops to near the backwash level, Then open the backwash water extraction plate gate. The improved backwash process significantly reduces equipment losses and saves water. The time of air washing and washing of filter backwashing should be adjusted according to the water quality. The new system will design the time of backwashing and washing to be adjustable to make the operation more convenient. The automatic operation of the sedimentation tank scraping bridge is controlled by the south limit switch and the north limit switch. If the limit switch is not pressed normally, the auto-run scraper bridge cannot stop, causing a serious accident that the scraper bridge drive motor burns. The program designer added time-out protection and alarms for the automatic operation of the scraper bridge, and increased the measurement and display of the running time, which facilitated the user and eliminated potential equipment hazards. The data communication between the Qinghe and Jiushuichang water intake management stations and the plant area was interrupted for many years. The new system realized wireless data communication between the Gang and Huangshui water management stations and the plant area, which ended the situation of contact between the plant and the post and the Yellow by telephone. The automatic control systems of the water intake stations of Qinghe and Jiushui Plants are relatively independent and are equivalent to the two enclaves of the water plant control system. After the new system is put into operation, the on-site data in the management station is transmitted to the water plant control system through wireless communication. The RTU used by the automatic control system of the Gangnan Water Management Station and the water intake flow meter of the water withdrawal management station are all third-party equipments using the MODBUS protocol, which realizes the interconnection of new systems and third-party equipment, and successfully restores plant and gang and yellow water. Wireless communication at the management station is a flaw in engineering design and implementation. Filter process diagram shown in Figure 5: Figure 5 filter control process 5 Conclusion In the automatic control system renovation project of the Beijing Surface Water Plant, a brand-new control network design concept was adopted. The software compatibility during the transformation process was successfully implemented. The control process was transplanted without affecting production, and the PLC program was optimized. Complete a number of process improvements, become the highlight of the entire project. Hengstar PIM series is a range of touch screen monitors for industrial automation such as: water/power supply system, factory automation system and CNC machine etc. Its ruggedized structure and durable performance ensure the monitor can work stable at harsh environmental conditions. Monitor's front bezel is made of black powder coated aluminum. The front plate is IP65 grade. 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