OPC UA including Ethernet TSN and Ethernet APL for the field: An intermediate goal has been achieved!
At SPS 2018, in Nuremberg, Germany the FLC initiative was founded under the umbrella of the OPC Foundation. A total of 27 companies, including the largest automation manufacturers in the world, have joined the initiative's Steering Committee, supporting it financially as well as with man-power and technical know-how.
The common goal is to expand the scope of OPC UA down to the field level and to establish OPC UA as a uniform and consistent communication standard in factory and process automation. In the technical working groups, which are open to all members of the OPC Foundation, a total of over 320 experts from more than 65 companies are currently working to develop appropriate concepts and specifications.
OPC UA at the field level - the system architecture
The extensions specified by the FLC Initiative are based on the OPC UA Framework (IEC 62541), which enables a secure and reliable, manufacturer and platform-independent information exchange. Controllers and field devices support both, the connection-oriented client/server communication model and the publish/subscribe extensions, which are indispensable for communication at the field level due to the corresponding requirements for flexibility, efficiency and determinism. The security mechanisms specified in OPC UA are also used, which, among other things, support authentication, signing and encryption of the data to be transported and can be used for both client/server and publish/subscribe communication relationships.
The initial release candidate of the FLC Initiative, completed in November 2020, consists of four specification parts (OPC UA Parts 80-83) and focuses on C2C communication (controller-to-controller) for the exchange of process and configuration data by means of peer-to peer-connections and a basic diagnosis.
Work on the safety solution for OPC UA (OPC UA Safety) is also very advanced. A first OPC UA Safety specification, which is based on client-server mechanisms which arose from a Joint Working Group with Profibus & Profinet International (PI), was already adopted in November 2019 (Part 15, OPC 10000-15). A revision of the OPC UA Safety specification will be available shortly, which describes the extensions for OPC UA publish / subscribe and the parameterization of safety participants. The special thing about the safety concept for OPC UA is, among other things, that safe participants can be dynamically integrated into the communication, with a unique identification, even while a machine or system is in operation.
Progress can also be reported with regard to motion. A working group has been developing an OPC UA-based motion solution since mid-2020. OPC UA Motion comprises the specification of motion control functions for various types of motion devices such as controllers, standard drives, frequency converters and servo drives. The FLC Steering Committee has agreed to base the work on the CIP Motion and Sercos specifications and to adapt them to the OPC UA information modeling and system architecture, taking into account the relevant Industry 4.0 use cases. The fact that, as with safety, existing concepts and specifications are being used, the specification work can be significantly accelerated.
The combination with TSN, APL and 5G
The OPC UA Framework is fundamentally transport-agnostic and can therefore be flexibly used with various underlying communication protocols and transmission physics. Ethernet Time-Sensitive Networking (Ethernet TSN) and the Ethernet Advanced Physical Layer (Ethernet APL) are considered by the OPC Foundation as important elements of the strategy to expand OPC UA to all use cases and requirements in factory and process automation and the vision to create a completely scalable, industrial interoperability solution.
The combination with TSN
By using Ethernet TSN, deterministic data transmission via OPC UA is facilitated, which is particularly indispensable for demanding automation applications. In addition, TSN allows different applications and protocols to be operated using standardized hardware and a common network infrastructure. This enables convergent industrial automation networks to be implemented in which various IT and OT protocols can coexist. A Working Group of the FLC Initiative is currently working out which TSN sub-standards shall be mandatory for OPC UA-based end devices and infrastructure components to meet the specified requirements for performance, flexibility and ease-of-use. The OPC Foundation has given a clear commitment to the TSN-IA (Industrial Automation) profile, which is being developed by the IEC/IEEE 60802 working group. For this reason, the OPC Foundation has entered into liaison agreements with the standardization bodies IEC SC65C and IEEE 802.1.
The combination with APL
Ethernet APL describes a physical layer for Ethernet that was specially developed for the requirements of the process industry. Ethernet APL enables data transmission at high speeds over long distances, the supply of energy and data via a common, twisted 2-wire cable, and protective measures for safe use in hazardous areas. This makes Ethernet APL the enabling technology for the use of OPC UA and other Ethernet-based protocols in the process industry. Due to the special importance of this technology, the OPC Foundation joined the Advanced Physical Layer (APL) project group in June 2020 to develop and promote APL together with other non-profit organizations and various industrial partners.
The combination with 5G
Data exchange via OPC UA is not limited to wired or wireless Ethernet communication. Support for the 5G mobile communications standard is also on the OPC Foundation's development horizon. The mapping to 5G will be seamlessly integrated into the existing OPC UA architecture, so that all protocol and profile extensions of the FLC initiative can be used, not only via Ethernet and Ethernet TSN, but also via 5G in the future.
The OPC UA (IEC 62541) framework, with extensions for the field level, specified by the FLC Initiative, in combination with underlying communication standards such as APL, TSN, and, in the future, 5G, offers a complete, open, standardized and interoperable solution. It not only fulfills the requirements of industrial communication, but, at the same time, enables consistency and semantic interoperability from the field level to the cloud and vice versa (Fig. 5). With this approach - in combination with the various companion specifications - information is made available with a standardized semantics directly at the data source.
Use cases to consider: A flow meter offers directly standardized "OPC UA flow measuring data" the moment the APL cable is plugged in. And analogously, servo drives directly process standardized "OPC UA drive setpoints” and provide standardized “OPC UA actual drive values” as soon as they are integrated into a machine network with Ethernet TSN.
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