The core task of the MES system is:
Correct and timely delivery of correct data information in the manufacturing process of the company, and immediate and accurate response to any abnormal changes in the production process. The goal is to: reduce the activities without additional value in the manufacturing process as much as possible, and optimize and recreate the company's production operations and processes.
Improve the real-time performance of MES system data and safeguard measures:
1. Analysis of data flow in MES system
1.1 The data application layer at the top of the system is responsible for analyzing, processing, and visualizing data in the system.
Through the B/S or C/S network architecture, the processed information is distributed to enterprise production management personnel at all levels.
1.2 The data processing layer located in the middle of the system is responsible for sorting and storing the collected data.
1.3 The data acquisition layer at the bottom of the system is mainly responsible for collecting various data information required by the system from various equipment devices such as DCS at the production site.
2. Improving the data acquisition, transmission and processing speed in the MES system To improve the real-time performance of the MES system data, the data collection, transmission and processing speed in the MES system must be improved.
The main links with this are the following links:
1. Data collection
2. Data transmission network
3. Real-time database
4. Application layer network architecture
5. User-end processing technology. Must take corresponding measures to deal with these five links.
3. Concrete implementation measures and safeguard measures
3.1 Data Acquisition Part of the data acquisition part is the basis of the entire MES system. For different acquisition targets, only targeted, reasonably appropriate and safe and efficient data acquisition methods and strategies can be used to obtain the fastest possible speed from field device installations ( The data is mainly acquired in various DCSs. Data Acquisition Methods for DCS Systems: Methods
1: The use of real-time database
The full English name of the OPC protocol for direct collection of OPC from DCS is OLE for Process Control, which is a standard interface technology for object linking and embedding for process control. It is based on the Microsoft Corporation.
Distributed interNet Application (DNA) architecture and Component Object Medel (COM) technology, designed for ease of extensibility. At the same time, OPC uses the OLE (ie, object linking and embedding)/COM (ie, component object model) mechanism as the communication standard of the application program, while OLE/COM is a client/server server mode with language independence and code. Reusability, ease of integration and other advantages. OPC standardizes the interface functions. Regardless of the form of the field device, the customer accesses it in a uniform manner. It is an open interface technology based on OLE technology, COM, and DCOM (ie, distributed COM) technology and has become the current industry standard interface.
Most of the new DCS devices support OPC data interface communication protocols. Theoretically speaking, real-time databases can be used to directly collect data from DCS. However, we have found in actual investigation that some companies use this method to achieve poor results. Some even appear to cause the DCS to "crash," and this is the biggest risk in implementing data collection. Through investigating and consulting relevant experts, we learned that the cause of this "disaster" is that the real-time database itself has a large amount of data throughput. When the real-time database collects large amounts of data directly from the DCS system, the DCS itself must also It takes a lot of machine time to respond to these data requests from the real-time database. Once the data request volume is too large to be processed by the DCS, it will cause the DCS to handle the response speed of other events, and it looks like a “crash†from a phenomenon.
Method 2: Set up an OPC server, which is collected from the DCS by the OPC server and then forwarded to the real-time database. To avoid repeating the mistakes of others, we adopt the following method: use an IPC as the data collection workstation and communicate data with the DCS through the OPC protocol. , and only read the data we care about most from DCS without any write operation. Practice has proved that this method is very safe and reliable, and it does not affect the rapidity of the entire system data update.
Method 3: An OPC server is established, and the OPC server reads data from the old DCS without an OPC interface through other protocols, and then forwards the data to the real-time database through the OPC protocol. 3.2 Data Transmission Network
When the data collection workstation collects real-time data at the site, the data is quickly forwarded to the real-time database server placed in the data machine room through the network. After various data processing, the application server uses WEB to allow all levels of management personnel of the enterprise to access the MES system through the internal office network. From this we can see the importance of the data transmission network throughout the process. From the previous introduction, we know that a complete MES system has its network structure divided into three parts: collection network, management network, and application network. Among them, the acquisition network refers to the network from the real-time database to the data collection workstation and the on-site collection object (DCS, etc.), and the management network contains the part from the real-time database to the relational database and the application server. The application network is From various types of application personnel's computer terminals to MES application servers and relational server parts. For Chitianhua Co., Ltd., the existing office network is the application network of the MES system. Since the office network has been transformed into a high-speed network with thousands of fiber optic cables and 100 MB to the desktop, the MES project has been completed. In the above, we only built and improved the collection network and management network within the MES system according to the principle of “high speed, stability, safety, and reliabilityâ€.
Specifically, the following measures have been taken:
Measure 1: Place the collection station next to the on-site collection object (such as DCS), and shorten the data transmission line distance between the collection station and the DCS as much as possible to ensure high-speed data transmission between them through the Fast Ethernet connection.
Measure 2: Place the real-time database, relational database, and application server in the company's data lab, install single-mode fiber from the data lab to various site collection points, install a core switch with fiber modules in the data lab, and install fiber optics at the site. The module's desktop switch, core switch and desktop switch of each collection point are directly connected by optical fiber. It does not perform optical-to-electrical conversion through the optical fiber transceiver to reduce transmission links and improve transmission efficiency.
Measure 3: The core switch adopts a four-layer switch with a backplane bandwidth of ≥100Gbps and a packet forwarding rate of ≥75Mpps. The backplane bandwidth of the desktop switch at the collection point is ≥4.4Gbps and the packet forwarding rate is ≥6.5Mpps. The server room uses a quad-core dual-CPU branded device with stable performance and strong processing capability. Site collection workstations use industrial computers with stable performance and high reliability.
Measure 4: On-site data collection workstations not only collect and forward data, but also store the data to be forwarded locally for more than 7 days. When the network is interrupted, the data can be automatically reissued to the real-time database after the network is interrupted. Network interruptions result in the loss of large amounts of data, maximally avoiding losses to the enterprise.
3.3 Real-time database
Needless to say, the core of the entire MES system is the real-time database. The performance of the real-time database itself will directly determine the performance of the entire MES system. The use of efficient data compression and storage technology can greatly increase the speed of data transmission and processing. Imagine downloading data files from the same server is to download hundreds of megabytes of large files or only a few megabytes or even a few K of files. What? Therefore, when we select a real-time database, we also use data compression and storage as important assessment indicators.
3.4 MES application layer network architecture
The MES system is used to provide access services to the application personnel in a WEB manner. Therefore, the network architecture of the application layer is divided into two types: B/S and C/S. So, how should these two kinds of structures be chosen? Taking into account the actual application of the company's various departments, in a few special positions (such as scheduling, general control, etc.) to set the client using C / S architecture, and other users access via WEB using B / S architecture. In this way, the entire MES system is actually a hybrid architecture of B/S and C/S.
3.5 client processing technology
In the MES involves a large number of graphic images need to be displayed on the user's computer screen, especially the process flow chart, the need to use realistic images to display the corresponding device device, if you use the traditional BMP or JPG format graphics file format The speed of the full screen display is very slow when browsing at the user end, especially when the status changes such as temperature and liquid level are dynamically displayed, it is even more difficult to achieve the effect that the interface display is both intuitive and fast. Therefore, this objective requirement is taken into account when formulating specific technical solutions. After repeated comparison testing, the user-end dynamic imaging technology based on vector graphics technology was finally selected. From the effect of actual operation, this technology is used by the WEB plug-in to generate graphics based on the data provided by the server on the browser of the user end, especially the flow chart of the technology, the display speed is very fast, and the screen effect is also more vivid and vivid. But also can achieve real-time dynamic display temperature, liquid level changes.
4, the overall effect evaluation
Due to the targeted methods and measures adopted in the above five aspects, the effect is more obvious at least in the real-time nature of the data, and the data seen by the user end is basically synchronized with the data of the on-site DCS device.
Shenzhen Shenkete Information Technology Co., Ltd. is committed to the research and application promotion of lean manufacturing intelligent management system and industrial automation technology. It can provide LEAN MES lean manufacturing execution system, WMS warehouse management system, APS scheduling system, intelligent electronics for manufacturing companies. Shelf, intelligent warehouse, intelligent logistics, non-standard automation design and deployment, and hardware and software one-stop solution for intelligent manufacturing plant overall planning.
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