Application of simultaneous communication between OPTO22SNAPI/O and various PLCs
1. Overview The Daqing oilfield natural gas red pressure cryogenic plant is the largest gas treatment unit of the natural gas branch company. It processes 900,000 square meters of natural gas per day and produces more than 200 tons of light hydrocarbons. According to the design requirements of the automatic monitoring system for natural gas cryogenic separation equipment, due to the extensive distribution of the relevant PLC equipment, the monitoring function requires a high degree of automation, and the relevant information should be quickly acquired and processed, and it should be easy to manage. Therefore, the automatic control system uses OPTO 22's SNAP I/O system as the backbone framework, combined with its extremely advanced and easy-to-use application development configuration software package Factory Floor Suit 4.0c, developed on the 32-bit WINDOWS operating system platform. It is easy to complete all kinds of monitoring functions of the system, and it also has the application software of automatic monitoring system for natural gas cryogenic separation device using a flexible man-machine interface. It monitors the temperature, pressure, differential pressure, regulating valve, electromagnetic valve and other process points in the process area. The compressors, expanders, propane chillers, ESD emergency stop systems, etc. in the plant communicate with the OPTO22 SNAP I/O system for data exchange. Because the unit's own PLC system comes from many manufacturers, the communication standards are different and the technical difficulty is high. .
Through continuous exploration and practice, we successfully completed the communication problems among multiple systems in a relatively short period of time, making the system highly reliable, compatible, and easy to operate, and saving investment for the project.
2, the requirements of the communication system
1) With real-time data transmission and communication capabilities, using the powerful communication advantages of OPTO22 products, real-time transmission of production data to OPTO22 SNAP I/O system.
2) Perfect security monitoring function. The OPTO22 SNAP I/O system receives the alarm signal from the unit communication and can timely record and execute the corresponding field control process.
3) Support multiple communication protocols;
4) Good Chinese man-machine interface;
5) Using industrial configuration software, easy to maintain, expand and upgrade;
3. Technology to realize red pressure cryogenic plant project consists of compressor control subsystem, expander control subsystem, propane engine control subsystem, ESD emergency parking subsystem and OPTO 22 company OPTO22 SNAP I/O control system (ME system) V. Partly composed. Among them, the first four systems only perform partial unit control and exchange data through network communication with the OPTO22 SNAP I/O control system. The OPTO22 SNAP I/O system (ME system) is at the heart of global control and monitoring throughout the system.
In this project, we use OPTO22 SNAP I/O control system OPTO22 SNAP LCM4 as the main controller, the controller CPU uses 32-bit Motorola 68EC030 processor, 4MB memory with battery backup, 2MB flash read-write memory, 4 Serial interface, a fixed RS-485, three can be set independently as RS-232/485. We use the controller's own serial interface for programming.
In field applications, we first analyze the ESD system. The ESD emergency stop system is the basis for the safety guarantee of the red press Cryogenic device. It is implemented using a SIEMENS S7-400 programmable logic controller. It is designed as a master station and does not have a host computer display device. The monitoring is performed entirely in the OPTO22 SNAP I/O. achieve. The communication port of COM0---COM3 of LCM4 controller of OPTO22 SNAP I/O control system can be set up as 232 or 485 way according to need, according to many communication experiments of the scene, communication can't be realized by standard MODBUS way. The main reason is that the ESD system uses the master mode. If you change to the slave communication mode, you need to replace all ESD software and hardware. The cost is too high to achieve. After further analysis of the ESD PLC, we decided to use the freeport communication method to connect the SIEMENS S7-400 communication port to the COM3 of the LCM4 controller compatible with its standard. Through the establishment of data exchange program, set the start code, parity effect, the number of bits per array, transmission baud rate and so on. During the debugging process, DCS received the data sent by ESD, but the stability was poor. In the online (ONLINE) program, it was found that an empty stack error sometimes occurred. When the program was running to communication, the logic was abnormal. After repeated analysis and multiple tests, the program was in the program. The data synchronization process was added. At this point, the communication with the ESD was completely normal, and communication between the DCS and the emergency stop system was realized.
When communicating with the compressor system PLC, the compressor system uses GE's 90-70. We use the MODBUS RTU method to compile the corresponding program. After the program is completed, it is downloaded, downloaded, and continuously debugged. connection.
On the basis of realizing the communication between the above two units, using the accumulated experience, according to the individual characteristics of the units, the communication between the DCS and all the units is realized.
II. System Structure and Configuration Scheme In this system, OPTO 22's advanced and mature OPTO22 SNAP I/O system is adopted. This is a three-tier distributed network that uses serial communication multiple retransmission technology. The system is composed of the monitoring host PC of the automation center and the OPTO22 SNAP-LCM4 main controllers of the four OPTO 22 units and seven front-end intelligent I/O units B3000 that can be distributed and installed. For related system structure diagram, please refer to the following figure Show.
In the three-tier network structure as shown in the figure, the uppermost layer is composed of PCs. It uses ETHERNET network connection as the man-machine interface of the monitoring system. It dynamically displays the real-time status of various equipment operations and displays and records the abnormalities of the equipment. Fault alarm, set the equipment's automatic running time and conditions, the operator can switch the system equipment to operate automatically or manually. In addition, as required by the user, the monitoring host can be set up as a Web server, and all monitoring pictures can be converted into Web pages. Users can use the standard Internet browser Internet Explorer on the local area network and the Internet to monitor and even control the system. .
The second layer consists of four OPTO 22 controllers, OPTO22 SNAP-LCM4. Each controller and monitoring host use Ethernet communication to form a monitoring network (C-Net). Two of the controllers are connected to the field I/O, and each controller is connected to the on-site PLC.
The third layer consists of multiple PLCs and seven I/O smart units B3000. I/O units and related controllers are composed of RS-485 and form an I/O network (I/O-NET). The distance between I/O units is 1000m, and a communication repeater can extend the distribution distance. In this way, the I/O unit and the I/O module can be distributed in the vicinity of the relevant devices, which minimizes the connection of signal lines and greatly reduces the chances of interference during signal transmission. The I/O unit directly obtains the working status and alarm signal of the equipment, the detection signal value of the equipment, and can automatically or manually control the operation of the equipment, perform local operations and adjustments on the relevant PID operation control loops, and greatly strengthens the system. Real-time control and quick response capabilities.
Conclusion It has been proved that OPTO22 OPTO22 and multi-unit PLCs are stable, convenient, and have good real-time performance and reliability. It reflects the OPTO22 OPTO22 SNAP I/O system's flexibility, versatility, and powerful communications features.
Through continuous exploration and practice, we successfully completed the communication problems among multiple systems in a relatively short period of time, making the system highly reliable, compatible, and easy to operate, and saving investment for the project.
2, the requirements of the communication system
1) With real-time data transmission and communication capabilities, using the powerful communication advantages of OPTO22 products, real-time transmission of production data to OPTO22 SNAP I/O system.
2) Perfect security monitoring function. The OPTO22 SNAP I/O system receives the alarm signal from the unit communication and can timely record and execute the corresponding field control process.
3) Support multiple communication protocols;
4) Good Chinese man-machine interface;
5) Using industrial configuration software, easy to maintain, expand and upgrade;
3. Technology to realize red pressure cryogenic plant project consists of compressor control subsystem, expander control subsystem, propane engine control subsystem, ESD emergency parking subsystem and OPTO 22 company OPTO22 SNAP I/O control system (ME system) V. Partly composed. Among them, the first four systems only perform partial unit control and exchange data through network communication with the OPTO22 SNAP I/O control system. The OPTO22 SNAP I/O system (ME system) is at the heart of global control and monitoring throughout the system.
In this project, we use OPTO22 SNAP I/O control system OPTO22 SNAP LCM4 as the main controller, the controller CPU uses 32-bit Motorola 68EC030 processor, 4MB memory with battery backup, 2MB flash read-write memory, 4 Serial interface, a fixed RS-485, three can be set independently as RS-232/485. We use the controller's own serial interface for programming.
In field applications, we first analyze the ESD system. The ESD emergency stop system is the basis for the safety guarantee of the red press Cryogenic device. It is implemented using a SIEMENS S7-400 programmable logic controller. It is designed as a master station and does not have a host computer display device. The monitoring is performed entirely in the OPTO22 SNAP I/O. achieve. The communication port of COM0---COM3 of LCM4 controller of OPTO22 SNAP I/O control system can be set up as 232 or 485 way according to need, according to many communication experiments of the scene, communication can't be realized by standard MODBUS way. The main reason is that the ESD system uses the master mode. If you change to the slave communication mode, you need to replace all ESD software and hardware. The cost is too high to achieve. After further analysis of the ESD PLC, we decided to use the freeport communication method to connect the SIEMENS S7-400 communication port to the COM3 of the LCM4 controller compatible with its standard. Through the establishment of data exchange program, set the start code, parity effect, the number of bits per array, transmission baud rate and so on. During the debugging process, DCS received the data sent by ESD, but the stability was poor. In the online (ONLINE) program, it was found that an empty stack error sometimes occurred. When the program was running to communication, the logic was abnormal. After repeated analysis and multiple tests, the program was in the program. The data synchronization process was added. At this point, the communication with the ESD was completely normal, and communication between the DCS and the emergency stop system was realized.
When communicating with the compressor system PLC, the compressor system uses GE's 90-70. We use the MODBUS RTU method to compile the corresponding program. After the program is completed, it is downloaded, downloaded, and continuously debugged. connection.
On the basis of realizing the communication between the above two units, using the accumulated experience, according to the individual characteristics of the units, the communication between the DCS and all the units is realized.
II. System Structure and Configuration Scheme In this system, OPTO 22's advanced and mature OPTO22 SNAP I/O system is adopted. This is a three-tier distributed network that uses serial communication multiple retransmission technology. The system is composed of the monitoring host PC of the automation center and the OPTO22 SNAP-LCM4 main controllers of the four OPTO 22 units and seven front-end intelligent I/O units B3000 that can be distributed and installed. For related system structure diagram, please refer to the following figure Show.
In the three-tier network structure as shown in the figure, the uppermost layer is composed of PCs. It uses ETHERNET network connection as the man-machine interface of the monitoring system. It dynamically displays the real-time status of various equipment operations and displays and records the abnormalities of the equipment. Fault alarm, set the equipment's automatic running time and conditions, the operator can switch the system equipment to operate automatically or manually. In addition, as required by the user, the monitoring host can be set up as a Web server, and all monitoring pictures can be converted into Web pages. Users can use the standard Internet browser Internet Explorer on the local area network and the Internet to monitor and even control the system. .
The second layer consists of four OPTO 22 controllers, OPTO22 SNAP-LCM4. Each controller and monitoring host use Ethernet communication to form a monitoring network (C-Net). Two of the controllers are connected to the field I/O, and each controller is connected to the on-site PLC.
The third layer consists of multiple PLCs and seven I/O smart units B3000. I/O units and related controllers are composed of RS-485 and form an I/O network (I/O-NET). The distance between I/O units is 1000m, and a communication repeater can extend the distribution distance. In this way, the I/O unit and the I/O module can be distributed in the vicinity of the relevant devices, which minimizes the connection of signal lines and greatly reduces the chances of interference during signal transmission. The I/O unit directly obtains the working status and alarm signal of the equipment, the detection signal value of the equipment, and can automatically or manually control the operation of the equipment, perform local operations and adjustments on the relevant PID operation control loops, and greatly strengthens the system. Real-time control and quick response capabilities.
Conclusion It has been proved that OPTO22 OPTO22 and multi-unit PLCs are stable, convenient, and have good real-time performance and reliability. It reflects the OPTO22 OPTO22 SNAP I/O system's flexibility, versatility, and powerful communications features.
The handheld addresser is used to program the address of the monitoring module offline. When in use, connect the two output wires of the handheld encoder to the communication bus terminal (terminal label 1, 2) of the monitoring module, turn on the black power switch on the right side upwards, and press "ten Add", [Subtract ten", [Add one place" and [Subtract one place" to program the address.
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