4 OPC Unified Architecture

Open Platform Communications Unified Architecture (OPC UA) is a machine-to-machine communication protocol that has become increasingly popular in industrial automation. The protocol is designed to provide a standard and secure way for different machines and systems to communicate with each other, regardless of the manufacturer, platform, or operating system.

The OPC UA protocol is based on a client-server architecture, where the client initiates the communication and the server provides the requested data. The communication is structured around a set of predefined services that define the interaction between clients and servers. These services include browsing, reading, writing, subscribing, and monitoring. OPC UA also provides a range of security mechanisms, including encryption, authentication, and authorization, to ensure secure communication between clients and servers.

The OPC Foundation is the organization behind the standard and with 678 members it has a very broad base. Its members include global players in the automation industry. For example: Siemens, Honeywell, Microsoft, Beckhoff, SAP, Yokogawa, ABB, Rockwell, Schneider Electric, Wago, Iconics. All members of the Foundation can be found in the OPC Foundation member list. The association was founded in 1994 and released the first version of OPC in 1996. Since then, it has been working very successfully and actively on the further development and dissemination of the OPC standard.

The current standard of the OPC specification is OPC UA (OPC Unified Architecture). It is the successor of the old OPC standard, which is called OPC Classic. Many installations of OPC servers are Classic OPC Servers until today. The old standard already very successfully solved the task of realizing data exchange in automation independent of the manufacturer and defined the basic interfaces. The disadvantage of OPC Classic was the lack of platform independence. OPC Classic is based on the Microsoft technologies COM and DCOM and therefore OPC Server and OPC Client installations were limited to Microsoft Windows operating systems and networks. With the increasing success of other platforms such as Linux, Web architectures, Cloud, IoT Devices, and CPS the distribution of OPC was limited.

One of the key advantages of OPC UA is its platform independence. This means that it can be used with different operating systems, programming languages, and hardware platforms. This makes it a popular choice for industrial automation systems, where different machines and systems need to communicate with each other seamlessly.

The OPC UA protocol has several features that make it a powerful and versatile communication protocol for industrial automation. One of these features is its ability to handle complex data types. OPC UA supports a wide range of data types, including numerical data, strings, arrays, structures, and more. It also supports user-defined data types, which allows industrial automation systems to define their own data structures for their specific needs.

Another important feature of OPC UA is its support for time synchronization. In industrial automation, precise time synchronization is critical for ensuring that different machines and systems operate in sync with each other. OPC UA provides a mechanism for time synchronization between clients and servers, which ensures that data is exchanged accurately and on time.

OPC UA also provides built-in diagnostics and error handling capabilities. These capabilities make it easier for industrial automation systems to detect and diagnose errors and faults that occur during communication between clients and servers. This helps to minimize downtime and ensure that the system is operating efficiently.

The security features of OPC UA are also worth highlighting. OPC UA provides several security mechanisms to ensure secure communication between clients and servers. These mechanisms include encryption, authentication, and authorization. Encryption ensures that data is transmitted securely over the network, while authentication ensures that clients and servers are who they claim to be. Authorization ensures that clients and servers have the necessary permissions to access the requested data.

One of the key benefits of OPC UA is its interoperability. Because OPC UA is a standardized protocol, different machines and systems can communicate with each other seamlessly, regardless of the manufacturer, platform, or operating system. This makes it easier for industrial automation systems to integrate different components and systems into a single, cohesive system.

In summary, OPC UA is a standardized, secure, and platform-independent communication protocol for industrial automation. Its versatility, reliability, and security make it a popular choice for a wide range of applications in the industrial automation sector with its support for complex data types, time synchronization, built-in diagnostics and error handling, and security mechanisms.