OPC UA: Data Communication Standard for Process Control

What is OPC Unified Architecture and how is it used in digital architecture?

OPC Unified Architecture—or OPC UA for short—was developed by the OPC Foundation as a successor to its OPC Classic model. It was designed to facilitate and advance the use and integration of digital technologies in automated manufacturing processes and systems. As a platform-independent, IP-based software interface, it uses a common language to enable the interoperability of all digital infrastructure in the industrial environment.

In other terms, its role within digital architecture is to act as a “universal translator” to get disparate machines to understand each other and exchange and use different information effectively. The goal here is to get the entire system to work as a seamless, unified whole. OPC UA is a service-oriented architecture and can access both real-time and historical data. As such, this architecture is very flexible, reliable, and scalable.

Businesses can use OPC UA in their digital infrastructure to unlock value in process control through synergy. It is therefore one of today’s leading standardized protocols used to connect the factory floor with large-scale business software. As a non-proprietary, open standard, it has been widely implemented by all industries.

What makes OPC UA different from OPC?

OPC Classic and OPC Unified Architecture vary in a few ways. The first main difference is that OPC UA is a newer and improved version of the traditional standardized protocol, OPC Classic. It features many of the same capabilities but also has some improved specifications such as:

Platform independence: One of the major drawbacks to the original systems architecture was that its communication was limited to Microsoft proprietary technologies. With OPC UA, connections are based on the transmission control protocol/Internet protocol (TCP/IP), which is compatible with a wide variety of software systems (e.g., Windows, Linux, MacOS, etc.) and could be embedded on other platforms as PC´s.

Enhanced security: The traditional OPC standard relied on the component object model (COM)/distributed component object model (DOM) for connecting the UA client and server. These models, however, are prone to cyberattacks because they do not have any built-in security mechanisms and generally rely on network firewalls for protection.

OPC Unified Architecture, on the other hand, has a suite of integrated controls and devices that restrict who/what can access information and authenticate and encrypt data from the start of transmission. It is thus more secure.

Scalable design: OPC UA, unlike OPC Classic, is extensible and can be leveraged for anything from mobile devices to cloud applications. Its multilayered architecture is capable of accommodating different resource constraints. New transport layers, security standards, data types, etc. can thus be added to keep pace with automation and the industrial Internet of Things (IoT).

What is an OPC client? And how is it different from an OPC UA server?

OPC UA communication typically involves two types of applications: an OPC client and an OPC server.

The OPC UA client is a controller that utilizes an OPC UA server to communicate with industrial end devices (hardware). It does this by initiating communication with the server through an authenticated connection.

The OPC UA server is OPC-compliant software that responds to OPC clients on the one end and communicates with industrial computers on the other. It can be seen as an intermediate agent that relays information between the OPC UA client and shop floor control equipment.

The OPC UA client has complete control over the OPC UA server. The OPC UA server therefore waits for incoming requests from the client, and it only performs actions as instructed by the client. The OPC UA server establishes connections to one or more end devices and converts the communication protocol used by these machines into a standardized set of OPC UA rules.

What are some OPC UA use cases?

Vertical integration: Thanks to OPC Unified Architecture, horizontal data exchange between embedded devices is not only possible but data between the lowest layer and higher levels can also be shared vertically. This vertical flow allows for the upward/downward movement of real-time data between field equipment, production and enterprise. Key personnel can thus access an entire plant’s operations to conduct many tasks, such as remote monitoring, device diagnostics, auditing and accounting, etc.

Event and alarm management: The OPC UA server can automatically monitor predefined events/alarms in systems and report them if necessary. For instance, if a cyberattack is made on remote field instruments, OPC UA may trigger an alert so that the respective devices can be shut down and prevented/restricted from accessing other networks or applications.

For example, Yokogawa's Collaborative Information Server also uses OPC UA for sharing data vertically.