Asset administration shell for the digital twin

US Industrial Internet Consortium and German Industrie 4.0 body propose ‘shell’ for digital twins. AAS is a standards-based ‘uniform regulatory framework’ for decentralized systems and artificial intelligence. Flagship implementation in SAP’s i40-aas. Initiative shows push-back from operations on IT encroachment.

A new white paper ‘Digital twin and asset administration shell concepts and application in the industrial internet and Industrie 4.0’ co-authored by representants of the US Industrial Internet Consortium (IIC) and the German Industry 4.0* body explores the relationship between the IIC’s vision for a digital twin and I4.0’s work on the asset administration shell, an overarching platform for plant and process industry automation.

In February 2020 the IIC produced a white paper, ‘Digital Twins for Industrial Applications’, with definitions, technical aspects, standards and use cases. The I4’s ‘Asset administration shell (AAS) is an implementation of the digital twin for industrial applications, developed to support cross-company-interoperability across the value chain.

The 30-page publication traces the history of the DT since the term was coined by Michael Grieves in 2003 in a course on product lifecycle management. The term was picked up by NASA in 2012 and defined as ‘a multi-physics, multiscale, probabilistic, ultra-fidelity simulation that reflects, in a timely manner, the state of a corresponding twin based on the historical data, real-time sensor data, and physical model’. Today, the DI is ‘about more than just simulation’.

There are other definitions, the DT, as a concept has grown to encompass, well just about anything, from data storage, analysis, control and AI. ‘Some implementations of digital twin may contain many attributes and data, computational capabilities and perhaps even a formal interface for communication to satisfy the application requirements, some others may only need a small set of attributes and data to be sufficient to support their application’. Your milage may vary.

In some senses, the DT represents push back from the operations technology community in reaction to the takeover of IT. The white paper has it that ‘The DT organizes and enables access to the data in association with its corresponding real-world objects from an Operational Technology (OT) perspective, rather than the usual data tables in databases from an IT perspective, making it better suited for running computational models and developing applications’.

The bi-directional nature of the DT is demonstrated by the fact that sensor data and operational states of an asset are sent continuously to the twin; any operational instructions resulting from decisions based on analytics in the specific application context can be sent back to the real-world entity to be executed’.

Under the hood computational and presentational models there are physical, statistical, control and machine-learning models, along CAD, engineering and visualization 3D applications including 3D simulation and VR/AR/MR. In a plant, twins can be combined into a hierarchy that mimics the whole system. In other use cases, twins can be combined in a peer-to-peer configuration, for instance in a windfarm.

Such combination requires a ‘common construct’ of data, models and a service API. Enter AAS, the asset administration shell, a standards-based ‘uniform regulatory framework’ for decentralized systems and artificial intelligence. AAS combines elements from the IIC’s Industrial Internet Reference Architecture and Industrie 4’s own ‘RAMI’. A ‘technology-neutral’ information model embeds technologies enumerated as ‘XML, JSON, RDF, OPC UA and AutomationML’. An offline-use file information exchange package format (AASX) is also available. Communications appear to favor MQTT and/or OPC-UA. The AAS claims alignment with the ISO/IEC standard ISO/IEC 21823-1 governing IoT system interoperability. Other AAC standardization activities are ongoing in IEC TC65 WG24 and ISO CD 23247. Examples of open-source AAS activity include the Admin Shell, BaSyx 21 and SAP’s i40-aas.

Comment. Industry 4 and the AAS probably have more to say about the discrete process industries (manufacturing) but the DT trope has so much currency in oil and gas that an awareness of how this large operations technology community sees the world may prove useful. What is also interesting is the parallel between an assemblage of digital twins, and the kind of interoperability promised by the IT communities push for ‘microservices’. As OSDU extends towards operations, these two worlds are getting closer!

* More strictly Germany’s Plattform Industrie 4.0.

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