OPC (OLE for Process Control), OLE for Process Control, is an industrial standard, the international organization that manages this standard is the OPC Foundation, the OPC Foundation has more than 220 existing members. OPC Foundation has more than 220 members worldwide, including all the world's major automation control systems, instrumentation and process control system companies. Based on Microsoft's OLE (now Active X), COM (Component Object Model) and DCOM (Decentralized Component Object Model) technologies, OPC includes a comprehensive set of standards for interfaces, properties and methods for process control and manufacturing automation systems.
Basic introduction Foreign name: OLE for Process Control Category: Software Suite Platform: Windows Features: efficiency, reliability, openness Definition Explanation, application domain, problem solving, Definition Explanation OPC is Object Linking and Embedding (OLE) for Process Control, which emerged as the foundation for the development of the OPC technology. OPC is known as Object Linking and Embedding (OLE) for Process Control, and it has created a bridge between Windows-based applications and field process control applications. In the past, in order to access the data and information of field devices, each developer of the application software needs to write a special interface function. Due to the wide variety of field devices and the constant upgrading of products, this often brought a huge workload to users and software developers. Usually this can not meet the actual needs of the work, system integrators and developers are in urgent need of a highly efficient, reliable, open, interoperable plug-and-play device driver. In this case, the OPC standard came into being. OPC standard based on Microsoft's OLE technology, it is developed by providing a standard set of OLE/COM interface to complete the OPC technology used in the OLE 2 technology, OLE standards allow multiple microcomputers to exchange documents, graphics and other objects. COM stands for Component Object Model and is the basis for all OLE mechanisms. com is a standard developed to implement programming language-independent objects that define objects under Windows as independent units that can be accessed without programmatic restrictions. This standard allows two applications to communicate through an object-oriented interface without needing to know how the other was created. For example, a user can create a Windows object in C++ that supports an interface through which the user can access the various functions provided by the object, and the user can write the object access program in Visual Basic, C, Pascal, Smalltalk, or another language. In Windows NT4.0 operating system, the COM specification is extended to access other objects outside the local machine, an application program used by the object can be distributed on the network, COM this extension is called DCOM (Distributed COM). Through the DCOM technology and OPC standards, it is possible to create an open, interoperable control system software. OPC adopts the client/server model, putting the task of developing access interfaces on the hardware manufacturers or third-party manufacturers, and providing them to the user in the form of OPC servers, which solves the contradiction between the software and the hardware vendors, completes the integration of the system, and improves the openness and interoperability of the system. OPC servers usually support two types of applications. OPC servers usually support two types of access interfaces, which provide access mechanisms for different program language environments. These two types of interfaces are: automation interface; and custom interface. The Automation interface is usually a standard interface defined for script-based programming languages and can be used by clients developing OPC servers in VisualBasic, Delphi, PowerBuilder, and other programming languages. Custom interfaces are standard interfaces developed specifically for high-level programming languages such as C++. OPC has now become the pre-defined solution for interconnecting systems in the industrial world, bringing convenience to industrial monitoring and control programming without users having to struggle with communication protocol difficulties. Any automation software solution provider, if it can not support OPC in all aspects, it will be eliminated by history. 1, in the control field, the system is often composed of decentralized subsystems; and subsystems often use different manufacturers of equipment and solutions. Users need to integrate these subsystems and architect a unified real-time monitoring system. 2, such a real-time monitoring system needs to address the decentralized subsystems between the data **** enjoy, the subsystems need to be unified to coordinate the corresponding control instructions. 3, taking into account the real-time monitoring system often need to be upgraded and adjusted. 4, there is a need for the subsystems to have a unified open interface. 5, OPC (OLE for Process Control) specification is the product of this thinking. 6, OPC based on Microsoft's Distributed interNet Application (DNA) architecture and Component Object Model (COM) technology, based on easy scalability and design. OPC specification defines an industry-standard interfaces. 7, OPC is to OLE / COM mechanism as the application of the communication standard. OLE / COM is a client / server model, with language independence, code reuse, easy to integrate the advantages of OPC specification of the interface function, regardless of the form of field devices, the customer to access a unified way to ensure that the software to the customer's transparency, so that the user is completely removed from the low-level development. The user is completely detached from the low-level development. 8, OPC defines an open interface on which PC-based software components can exchange data. It is based on Windows OLE - Object Linking and Embedding, COM - Component Object Model (Component Object Model) and DCOM - Decentralized COM (DCOM). DCOM - Distributed COM (Distributed COM) technology. As a result, OPC provides an ideal method for connecting typical field devices at the automation level to industrial applications and office programs. Application areas 1, industrial control solution users 2, building control solution users 3, industrial control solution vendors 4, building control solution vendors 5, industrial control solution integrators 6, building control solution integrators 7, all areas of automation OPC is designed to connect between the data source (OPC server) and the user of the data (OPC application) software interface standards. The data source can be PLC, DCS, barcode reader and other control devices. With the different composition of the control system, as the data source of the OPC server can be and OPC application program in the same computer running on the local OPC server, can also be in another computer running on the remote OPC server. The OPC interface is suitable for both the raw data of the lowest level control equipment through the network to the HMI (hardware supervisory interface)/SCADA (Supervisory Control and Data Acquisition), batch processing and other automation programs as the user of the data (OPC application), as well as the upper level of the history database and other applications, but also for the application and the physical device directly connected. Therefore, the OPC interface is an interface standard with high thickness and flexibility for many systems. Problem solving Before OPC was created, there was no standardized interface between the drivers of the hardware and the applications connected to them. For example, in the FA (FactoryAutomation) - factory automation field, connecting PLC (Programmable Logic Controller) and other control devices and SCADA / HMI software, need to be different from the FA network system composition. According to the results of a survey, in the control system software development costs, a variety of machine application program design accounted for 70% of the cost, while the development of machines and equipment to connect the interface between the 3%. In addition, in the PA (Process Automation) - process automation field, when it is hoped that the decentralized control system (DCS - Distributed Control System) in all the When wishing to transfer all process data from a decentralized control system (DCS - Distributed Control System) to a production management system, it is necessary to develop specific interfaces according to each machine type of each supplier, for example, by using the C language DLL (Dynamic Link Library) to connect to the DDE (Dynamic Data Exchange) server or by using the text of the FTP (File Transfer Protocol) to design the application program. If the system consists of four control devices and three applications for monitoring, trending, and reporting connected to them, it takes a lot of time to develop the interface software for monitoring, trending, and reporting applications corresponding to devices A, B, C, and D, respectively, and a total of 12 types of drivers are required. At the same time, it is difficult to maintain the stability and reliability of the operating environment due to the wide variety of drivers stored in the system. OPC is proposed for the purpose of standardizing the software interface between devices and applications from different suppliers and simplifying the exchange of data between them. As a result, it is possible to provide users with process control software components that can be freely combined and used without relying on a specific development language or development environment. A system utilizing OPC consists of an OPC server that provides data acquisition services according to the requirements of an application program (client program), an OPC interface necessary to use the OPC server, and an OPC application program that receives the services. the OPC server is developed according to the hardware of each supplier, so that differences in the hardware and systems of each supplier can be absorbed to realize a system composition that is not dependent on the hardware. The OPC server is developed in accordance with the hardware of each vendor so that it can absorb the differences in the hardware and system of each vendor, thus realizing a hardware-independent system composition. At the same time, by using a data type called Variant, it is possible to provide the data format according to the requirements of the application program without depending on the data type inherent in the hardware. By standardizing the interface with OPC, monitoring, trending, and reporting applications can be selected independently of the internal structure of each device and its vendor. Why develop independent OPC Server and OPC Gateway? 1, the original foreign manufacturers of high prices 2, the original foreign manufacturers to face the project's inflexibility 3, the diversity of subsystems in the domestic project is difficult to provide DRIVER 4, the independent OPC Server is the pursuit of stability, real-time, fast. 5, the many subsystems of the non-standardized 6, the turnkey project before and after the bidding inconsistencies that may occur 7, expensive original platform server software 8, the turnkey contractor integration whether to invest a lot of manpower to develop 9, the compatibility of platforms and subsystems 10, the establishment of the OPC platform and subsystems of the interoperability of the 11, to solve the vendors and integrators in the project integration of the troubles 12, to solve the vendors and integrators to decentralize the resource For secondary development 13, to solve the project subsystem vendors in the trouble 14, for the upper and lower bits of data communication to provide a transparent channel