Tips for getting started with OPC UA for machine manufacturers
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- Automation
- 31.5.2023
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Contents
The path to an OPC UA standard is so complex for many machine manufacturers that they shy away from it, not even attempting an approach.
But there are many tools and aids that can help companies to get started and to avoid mistakes and setbacks.
The completion of IEC 62541 has formally established OPC UA as an international standard; as part of the Reference Architecture Model Industry 4.0 (RAMI 4.0), it is also closely intertwined with the Industry 4.0 concept that paves the way from mass production to custom-made production (“batch size 1”). A number of enabler technologies are required in order to capture the individual characteristics of a product and adjust the production accordingly.
This includes the modularization of the production environment as well as the greater flexibility and broader functionality of machines and systems, which in turn can result in increased communication requirements in numerous OPC UA product solutions. This requires in particular the machine-readable description of the manufacturing functions as defined by the Capability, Skill and Service (CSS) model. This creates an essential foundation for the desired smart manufacturing.
More sophisticated development projects, more data points and the increasing use of artificial intelligence increase the complexity and make the automation as well as the monitoring of production and manufacturing processes more and more difficult. This is true in particular of the brownfield—when system parts are not all sourced from the same manufacturer. This can make it difficult to integrate the necessary information in a common user interface and to obtain a detailed complete overview.
This is where OPC UA can shine. Not only does the data and communication standard help transfer process data and status information into a single uniform format so that all relevant data can be processed together, its central concept—the use of data models—also makes it possible to describe the data context using semantic meta information, ensuring that all data streams can be utilized across manufacturers and platforms. It meets the requirements of the CSS model.
Sector-specific UA Companion Specifications ensure that standardized data models are introduced in numerous industries, making it possible to integrate not just basic functions but also higher-value services in the spirit of Industry 4.0, independent of the manufacturer.
Why OPC UA standardization is worth the effort
It is true that getting started with OPC UA is not that simple because it requires more than simply transferring or formatting data in a certain manner. Rather, an understanding of the data must be developed, and this understanding must be translated into a formal structure that can be machine-processed—the data model. This means that applying OPC UA requires more than just integrating a framework, an API collection or a mapping tool.
On the other hand, the data model concept has been implemented in such a stringent and universal manner that one does not have to overcome huge comprehension obstacles in order to get started with the technique.
Whoever is already using OPC UA should remain on the ball in order to realize both sector-specific and global specifications. At this point in time, the development is progressing rapidly and there are constant updates and changes.
This includes for example the “OPC UA for Machinery”, a multi-module specification that encompasses data models for numerous basic functions. It is a product of the close cooperation between several working groups and the overarching coordination by the OPC Foundation, which puts the parallel developments in different industry extensions—the OPC Companion Specifications (CS)—onto a common basis. This simplifies the implementation of multiple such extensions later.
The results of these standardization efforts speak for themselves. For example, a robot can communicate and interact with an injection molding machine without the need for any specially created explicit program. Concepts such as “Plug & Produce” also require standardized or semantic information models like those provided by OPC UA.
Another interesting addition is the UAFX extension, i.e. the extension of the basic OPC UA functions to encompass communication at the field bus level. It includes standardized information models for controllers and field devices and thus permits low-level communication in the production landscape, for example between a saw and a press.
A semantic validation automatically checks possible interactions and interoperability—whether the two machines can “talk to each other” and whether they provide the functions required to complete the pending job. At the same time, new communication standards such as TSN can be used in order to support real-time enabled traffic in heterogeneous networks.
How to get started with OPC UA
A prerequisite is the appropriate automation and programming know-how. Another important step is the analysis of your own environment with regard to standardization issues. This depends on the specific industry or domain in which you are active, because standardization is not progressing at the same pace everywhere.
The packaging industry and the plastics industry are examples of domains that are already quite far advanced. In these industries, existing standards such as PackML and Euromap have already been fully transferred to the OPC UA model. Consequently, any machine in this area requires an OPC implementation based on the corresponding Companion Specifications. A similar development can already be observed in the wood processing industry.
A central source of information about current developments is the VDMA industry association. It brings together more than 50 working groups who work on the standardization of additional Companion Specifications and other OPC UA extensions; their work also extends to test-beds and use cases. This is a place where machine manufacturers cannot just obtain information but also actively collaborate and introduce their own ideas.
This leads to another question you should contemplate: What is the desired trajectory of your business model, and what does that mean for the future? Because nothing would be worse than taking decisions today that conflict with the goals of tomorrow. Typically, the strong networking in the industry helps you recognize sustainable trends and avoid expensive development mistakes.
Anyone joining the CS working groups does not need to worry about having to reveal their entire domain know-how or internal programming information. The Companion Specifications are always limited to just a part of the possible functions—the smallest common denominator that can be agreed upon. This leaves plenty of room for the manufacturer-specific functions, called “vendor-specific extensions”.
In this manner, OEMs can continue to use the functionality of their machines and systems to stand out from the competition, and at the same time implement common industry standards in these machines and systems so that they are interoperable with the existing systems and applications customers already own.
Shortcut on route to the standard: KEBA’s solution
Even with standardization, the effort required to implement the OPC UA Companion Specifications must not be underestimated. It is not enough to download an SDK and install a stack, because the SDK is only a basic service that must be integrated into a product (e.g. a PLC). Using an SDK to implement all items of a complex Companion Standard Definition such as Euromap 77 for the plastics industry takes about nine to twelve months of development time for an engineer, as experience has shown.
In order to support its partners in the implementation of the OPC UA standard, KEBA has developed a solution that can reduce this development effort to about one to three months. Proprietary information models as well as the information models from the Companion Specifications that come as NodeSet XML files for the OPC UA server can be loaded into the new KEBA automation suite.
The NodeSet file contains both the file type definitions of the information model and the semantic description of the available instances. An editing tool is used to modify this information in conformity with the standard so that manufacturer-specific extensions can be added.
This initially creates a modified information model in the OPC UA server containing all data types and instances; the semantic connection of your own application is next. KEBA’s solution takes care of mapping variables, methods and alerts between the applications and the information model in the OPC UA server. This sounds easy, but it is a complex process because some variables can be complex objects that must be disassembled into their components by the KEBA solution so that they can be represented at the application level—and vice versa.
“Non-OPC” niches will all but disappear in the not-too-distant future
Relief for SMEs
The benefit for developers is that they do not have to delve so deeply into the details of OPC UA technology or develop in-depth know-how. What is important is to know which data objects are present or needed at the server level and how these must be linked to the application. But this semantic connection is always a necessary part of creating an application. The mapping of the variables by the KEBA solution is done exclusively via configuration. This step does not require any actual coding.
This creates an efficient nexus between the two worlds: the applications on one side, and the standardization on the other side. The application world is already the home of the developer; his contact with the standardization world remains limited, which speeds up the implementation enormously. This is also true for application maintenance. Because KEBA’s proprietary mapping uncouples the application from the OPC UA server, changes to the application can be made without requiring the information models to be changed at the same time.
Such a solution provides relief in particular to small and mid-sized machine manufacturers who often lack the resources for recruiting OPC UA experts on the labor market or building up the required know-how within their existing team. At the same time, they are under pressure from their customers to comply with OPC UA specifications. In addition to the tool, KEBA is also happy to provide its partners with application engineers who can help and support them as they get started with OPC standardization, speeding up the time to market.
OPC UA cannot be avoided
Industry 4.0 is a trend that cannot be stopped. Just a few years ago, there was a serious discussion along the lines of: “Do we really need this?” The market has provided the answer: “Yes, absolutely.” Now we are seeing the same development in the implementation. OPC UA is the technology that has proven its worth in the real world for years. Due to the broad support in many industries and its consistent structure, more and more customers are viewing this standard as a must-have. In the long run, it cannot be avoided; “non-OPC” niches will all but disappear in the not-too-distant future.
And while OPC UA is a powerful tool for realizing the Industry 4.0 concept, it also places high demands on developers. Because this is a complex matter, and to make things worse, it is still in flux as the development progresses in leaps and bounds.
Solutions such as the one offered by KEBA provide welcome relief. The configurable mapping reduces the programming effort and requires less OPC UA know-how. This creates the ideal conditions for getting started with the implementation now, so as not fall out of step with this inevitable development in the market.
