Introduction to OPC
OPC (OLE for Process Control, process control object connection) is a technology widely used in the field of industrial automation, which allows communication and data exchange between automation equipment from different manufacturers.
OPC technology was first launched by the OPC Foundation, a software company in the United States. It realizes data exchange and information sharing between different automation devices through a series of standards, specifications and interfaces. OPC technology has become an indispensable part in the field of modern industrial automation. The full name of OPC is Object Linking and Embedding (OLE) for Process Control, and its appearance has established a bridge for Windows-based applications and on-site process control applications.
OPC History
OPC technology was first launched by the OPC Foundation, an American software company. Before 1995, there was no standard communication protocol between automation equipment in the industrial field. Each manufacturer has its own communication methods and protocols, which brings great difficulties to the realization of data exchange between devices.
In this context, OPC technology came into being. It realizes data exchange and information sharing between different automation equipment through a series of standards, specifications and interfaces. OPC technology has been widely used and promoted in a short period of time, and has become an indispensable part in the field of modern industrial automation.
OPC principle
The essence of OPC technology is to standardize and normalize the data between automation equipment, so as to realize data exchange and information sharing. In order to achieve this goal, OPC technology introduces some core concepts and conceptual models.
OPC server
An OPC server is a piece of software that acts as a source and consumer of data. The OPC server can communicate and exchange data with other automation devices through some specific interfaces and protocols. The OPC server is responsible for reading data from automation equipment, processing data and sending data to other automation equipment.
OPC client
An OPC client is another piece of software that communicates with an OPC server. The OPC client is responsible for requesting data from the OPC server, processing the data and displaying the data to the user or other automation equipment.
OPC standard
The OPC standard refers to a set of specifications, protocols and interfaces. These specifications, protocols and interfaces define the communication methods, data formats and data transmission processes between automation devices. The OPC standard enables data exchange and information sharing between automation equipment from different manufacturers.
OPC Object Model
The OPC object model refers to an object-based data management and transmission model. In this model, all data is abstracted into individual objects, and each object has its own properties and methods. The OPC object model can help achieve efficient data exchange and information sharing between automation equipment from different manufacturers.
OPC classification
According to different standards, norms and interfaces, OPC technology can be further divided into different types. Here are a few common categories.
OPC Classic：
OPC Classic: Divided into two parts - OPC Data Access (DA) and OPC Historical Data Access (HDA).
OPC YES
OPC DA (Data Access, data access) is one of the earliest OPC standards. This standard defines some interfaces and protocols that allow OPC servers to provide real-time, dynamic data to OPC clients. The OPC DA standard was originally developed for time-sensitive data in the field of industrial automation, such as temperature, pressure, etc. OPC DA is an obsolete OPC technology, it can only communicate on the Windows platform, and it can only be used for real-time data transmission, not for historical or reporting functions.
OPC HDA
OPC HDA (Historical Data Access) is a standard developed for historical data access in industrial automation. It defines some interfaces and protocols that allow OPC servers to provide historical data to OPC clients. The OPC HDA standard can help enterprises analyze and judge production data, thereby improving production efficiency and quality.
OPC UA
OPC UA stands for OPC Unified Architecture, which is a new type of OPC technology that allows cross-platform and cross-device communication on different platforms (Windows, Linux, Android, etc.) and different devices (PLC, sensors, etc.), And has stronger security and scalability. OPC UA is more flexible, secure and reliable than OPC DA, and is considered to be the standard for future industrial communication.
OPC A&E
OPC A&E (Alarm & Event, alarm and event) is a standard developed for alarm and event information in the industrial field. It defines some interfaces and protocols that allow the OPC server to transmit alarm and event information to the OPC client to help monitor and control the production process.
Advantages of OPC
OPC has the following three characteristics:
1. Computer hardware manufacturers only need to write a set of driver programs to meet the needs of different users. Hardware suppliers only need to provide a set of programs that conform to the OPC Server specification, without considering the needs of engineering personnel.
2. Application developers only need to write an interface program to connect different devices. Software developers do not need to rewrite a large number of device drivers.
3. Engineers have more choices in equipment selection. For end users, according to the actual situation, they can choose the actual equipment.
OPC application scenarios
OPC is widely used in industrial control, intelligent manufacturing, automatic production and other fields. For example, in chemical, food, pharmaceutical, automotive and other industrial fields, OPC can connect different sensors, instruments and control systems to realize functions such as data collection, monitoring and control, and production scheduling. In the field of intelligent manufacturing, OPC can realize the interconnection between different devices, thereby improving production efficiency, reducing costs, and improving security.
Application of OPC and PLC:
In industrial automation control, PLC (Programmable Logic Controller) is one of the most commonly used controllers. The combination of OPC and PLC can realize data sharing and control operation between PLC and other devices and systems. For example, when the PLC controller needs to control different devices, the OPC server can manage them uniformly and send corresponding instructions and control signals to the PLC.
Application of OPC and SCADA:
In industrial automation control, SCADA (Supervisory Control and Data Acquisition) is a software system for monitoring and controlling distributed equipment and systems. OPC can connect different SCADA systems to realize data sharing and control operations. For example, when multiple SCADA systems need to monitor and manage the same device, they can be connected and interacted through the OPC bridge to achieve a more flexible and efficient operation.
Application of OPC and MES:
In the manufacturing execution system (MES), OPC can connect different production lines, stations and equipment to each other and share data, so as to realize production scheduling, material management, quality monitoring and other functions. For example, in the production line, when the equipment fails or the process changes, OPC can detect and analyze the equipment status through the MES system, and give corresponding control operations and alarm prompts to ensure the efficient operation of the production line and the stability of product quality sex.
In short, OPC can play an important role in the fields of industrial control, intelligent manufacturing, and automated production, enabling various devices and systems to connect and share data, improve production efficiency, reduce costs, and improve product quality and safety.
Comparison of OPC and other technologies
In the field of modern industrial automation, in addition to OPC technology, there are some other communication and data exchange technologies, such as MODBUS, PROFIBUS, CAN, etc. What are the advantages and disadvantages of these technologies compared with OPC technology?
OPC and MODBUS
MODBUS is one of the most common communication protocols used for communication between slaves and masters in the field of industrial automation. Compared with OPC technology, the advantage of MODBUS is that it is simpler and easier to implement, and it can communicate between various types of hardware platforms. However, the disadvantage of MODBUS is that it does not support complex data types, such as strings, dates, times, etc. At the same time, MODBUS also lacks various advanced functions and data processing capabilities of OPC.
OPC and PROFIBUS
PROFIBUS is a digital communication network used in industrial automation. Compared with OPC technology, the advantage of PROFIBUS is that it can realize real-time, high-speed data transmission, and has a wide range of applications in industrial automation control systems. However, the disadvantage of PROFIBUS is that it does not support cross-platform data exchange, and the communication methods and protocols are more complicated and require a higher technical level.
OPC and CAN
CAN is a communication protocol used in automotive electronic systems. Compared with OPC technology, the advantage of CAN is that it can realize high-speed and reliable data transmission between different electronic controllers, thus improving the reliability and performance of automotive electronic systems. However, the disadvantage of CAN is that it can only be used in automotive electronic systems and cannot be used in other types of industrial automation equipment.
Summarize
OPC technology is the most widely used technology in the field of industrial automation. It realizes data exchange and information sharing between different automation equipment through a series of standards, specifications and interfaces. OPC technology can help enterprises to monitor and control the production process, thereby improving production efficiency and quality. When choosing OPC technology, it is necessary to consider the differences of different standards, specifications and interfaces, and choose the appropriate OPC type according to actual needs.