At the heart of the Industrial IOT (IIOT) OPC UA addresses the need for standardized data connectivity and interoperability for both horizontal and vertical data communications. This page is designed to be a good primer on OPC UA.
OPC UA stands for Open Platform Communications Unified Architecture. OPC Unified Architecture (OPC UA) is an extensible, platform-independent standard that enables the secure exchange of information in industrial systems.
OPC UA was released in 2008, by the Open Platform Communications (OPC) Foundation, which regulates and maintains the interoperability standard, protocols, and specifications for data communication, in industrial automation operations.
Industrial interoperability is a challenge. Many protocols and technologies are being in use in the industry. Everybody is wasting a lot of time and money doing the same thing in 200 different ways. Like TCP/IP is the single way to communicate over the internet, we needed a single way of communicating between Industrial equipment.
The Reference Architecture Model for Industrie 4.0 (RAMI 4.0) recommended only the IEC standard 62541 OPC Unified Architecture (OPC UA) for implementing the communication layer.
Using models, OPC UA specifies basic rules for exposing data to any application or device that wants to consume it. Open Platform Communication Unified Architecture (OPC UA) itself is an information-centric data model.
OPC UA comprises a generic object model with an extensible type of system with built-in models for data access. These built-in models specify functions such as alarms and events information, information about historic data, data access details, device descriptions, and to execute programs.
Data can also be accessed through custom models, which are referred to as companion models. Some industry specific companion specification examples are oil and gas (MDIS), pharmaceutical (Open SCS), plastic and rubber machinery (EUROMAP).
OPC Unified Architecture (OPC UA) is used in industrial systems, for example, oil and gas, agriculture, medical and pharmaceutical, critical services like electricity grids and sewerage treatment plants, and IoT systems like smart city applications.
Common OPC UA applications include device diagnostics, asset management, production management, quality control, data acquisition, enterprise reporting, data security, data integration for GUI interfaces, remote worker support, and event monitoring.
Open Platform Communications Unified Architecture (OPC UA) also supports the industrial internet of things (IIoT). For example, OPC UA may be used to push data from embedded devices like temperature sensors to the cloud to analyze usage and equipment efficiency.
OPC UA operates at the application, presentation, and session layers in the OSI model and will leverage TCP, UDP transport over a variety of wired and wireless networks.
You don’t have to deal with OPC UA as long as you don’t have to interoperate with other equipment. If you do have to interoperate with other equipment on the factory floor, you may as well want to use the same technology basics to communicate with the cloud.
Unfortunately, all existing cloud technologies cannot deliver on horizontal deterministic use cases. OPC Unified Architecture (UA) lets you model all your information in one place and send data horizontally or vertically.
In our opinion, the benefits far outweigh the complex argument that is generally placed against Open Platform Communications Unified Architecture (OPC UA).
OPC Unified Architecture (OPC UA) is designed to support a wide range of systems from PLCs in production to enterprise servers. These systems are characterized by their diversity in terms of size, performance, platforms, and functional capabilities.
To meet these objectives, OPC UA specifies the following basic functionalities:
OPC Unified Architecture (OPC UA) defines base building blocks and consistent rules to build object-oriented models with them. In OPC UA it is possible to expose and discover information models in a consistent and universal way between all OPC UA entities.
Open Platform Communications Unified Architecture (OPC UA) defines a few industry-agnostic information models that other organizations use as a common starting point to define their own OPC UA based information models.
OPC Unified Architecture also facilitates dynamic discovery and access to OPC UA information models.
You are the best judge. Do visit our Learn OPC UA online courses and take an informed decision. We have 3 different courses for software programmers, embedded system engineers, and control engineers.
OPC UA Client-Server communication is based on the service-oriented architecture (SOA) paradigm. Classic web services describe their services using XML-based Web Services Design Language (WSDL), thereby allowing each service provider’s implementation to be different.
Open Platform Communications Unified Architecture (OPC UA) predefines generic, standardized services to ensure all OPC UA implementations are compatible, and thus interoperable.
OPC Classic, the predecessor of OPC UA, relies on Microsoft technologies, while OPC UA is platform independent. OPC Classic does not have built-in security for access control, authentication, and encryption.
OPC Unified Architecture (OPC UA) enables data encryption at the data source, ensuring secure transmission without relying on network firewalls at the system’s core. Open Platform Communications Unified Architecture (OPC UA) implements cross-platform security based on the public key infrastructure (PKI) using industry-standard x.509 digital certificates.
In contrast to OPC UA, OPC Classic does not support dynamic information modeling, which allows manufacturers to define custom data models depending on the requirements of their industry.
OPC Unified Architecture (OPC UA) is based on several standards and protocols carefully chosen based on their ability to meet the needs of specific OPC UA use cases. For example:
Open Platform Communications Unified Architecture (OPC UA) standard is a collection of specifications (OPC UA protocols) that define guidelines for communication between servers and clients, including rules for different functions and data structures. It includes the following specifications:
Each specification is intended to address a common problem in industrial systems’ communication networks.
Security is built into the OPC UA architecture from the ground up and aligns with the security infrastructure provided by most web-enabled platforms.
User-level security mechanisms are engaged when a session gets established. An OPC UA client transmits an encrypted security token that identifies the user to the OPC UA server, which then authenticates and authorizes access to appropriate objects.
Application-level security includes the exchange of digitally signed certificates, instance certificates that identify the concrete installation, and software certificates that identify the client and server software and the OPC UA profiles.
Transport level security provides integrity via message signing and confidentiality via message encryption.
Security modes supported by OPC UA server are ‘None’, ‘Signed’, ‘Signed and encrypted’.
Enabling discovery service in OPC UA server lets the OPC UA client find OPC UA Servers with their supported protocols and security policies along with the other capabilities supported by the OPC UA server.
You can create a subscription for data change of a node in the OPC UA client. This will notify the client if there is a value change in the node of the OPC UA server.
OPC UA is more than just a protocol. Protocols such as DDS, AMQP, or MQTT are concerned with the transfer of data between applications, devices, and systems. They do not implicitly provide any context for the data being transferred.
Instead, it is up to the user to define the content of the data. As a result, it does not guarantee that the transferred data can be interpreted by a receiving system.
OPC UA addresses this by including definitions not only of data and information types but also of the device or application which generated the data using a common object definition library (OPC UA refers to these as ‘companion specifications’).
Hence, any system implementing the Open Platform Communications UA (OPC UA) architecture is guaranteed to be able to natively connect to and interpret data from any device which supports the same companion specs.
Sparkplug is an implementation that relies on MQTT. OPC UA PubSub can use MQTT as a transport layer. OPC UA PubSub can also achieve deterministic use-cases which Sparkplug cannot.
If we have a world where interoperability has to become simpler, every piece of equipment must digest the complexity of Linux + OpenSSL + OPC UA just as the way mobile phones at some point came to terms with the complexity of Android OS over competitors like Symbian or Blackberry OS.
OPC UA PubSub can be brokerless or broker-based. OPC UA PubSub in a brokerless fashion can function over TSN networks and provide highly deterministic systems.
OPC UA PubSub in a broker-based network (say using MQTT as the transport layer) can help move data from the edge to the cloud securely while remaining lightweight.
At this moment, if you are choosing ROS2, then you will bind yourself to DDS. Also, you cannot eliminate OPC UA. This means you will have two islands and you need to build a bridge in between.
People are used to smartphones and just-in-time services. They expect the same from every aspect of their life. Large industrial consortiums are coming together to find a solution to this problem with technology such as OPC UA.
An industry-specific standard through a companion information model reduces the duplication of effort to integrate the equipment as part of a larger process. Several companion specifications have already been created for industries such as CNC machine tools, plastics, and rubber processing machinery, packaging machinery, etc.
The basic features include, representing data through an information model that you can browse, read and write from a client application, supporting execution of methods, and sending notifications for data changes and events.
Historical access enables the client to access historical variable values and events. It can be read from the server that stores the data in the database, an archive, provided the OPC UA server supports historical access.
They will exist as two different networks with a gateway in between.
As of date, there is no active work on ROS2 to enable communication via OPC UA PubSub.
Nano embedded server profile. This profile is a full featured profile intended for chip level devices with limited resources. This Profile is functionally equivalent to the Core Server Facet and defines the OPC UA TCP binary protocol as the required transport profile.
In the traditional Client-Server model, a server receives a request from clients and sends the results back. Though this communication model is feature rich and simple, it is not feasible for some scenarios such as high frequency data and event notifications between large number of sending and receiving devices such as sensors, actuators and PLCs.
These devices are power, and latency constrained. This led to the OPC foundation releasing the pub-sub extension as part 14.
PubSub provides an alternative mechanism for data and event notification. It is optimized for many-to-many interactions where multiple clients may receive broadcasted notifications in a fire-and-forget fashion.
With brokered PubSub, OPC UA applications do not directly exchange requests and responses. Instead, Publishers send messages to Message Oriented Middleware without any knowledge about the Subscriber(s).
Open Platform Communications Unified Architecture (OPC UA) also supports brokerless PubSub for deterministic machine-to-machine use cases.
You can use standalone OPC UA Pub Sub defined in the Pub Sub specification part 14 to eliminate the need for server, thereby keep the implementation lean.
Have a look at the list of FLC members. If all these companies have come together to sit and discuss a problem, it should be something big and it should also mean that all their customers want them to lock heads and solve.
A few notable advantages of OPC UA include: