Asset administration shells: From concept to realisation

The implementation of asset administration shells requires uniform regulations for describing technical components and machines, i.e. standards. It is not without reason that asset administration shells form the information layer of RAMI 4.0. Organisations such as the IDTA (Industrial Digital Twin Association) and "Plattform Industrie 4.0" are also continually introducing new standards.

The contents of a specific asset administration shell can sometimes be highly specific. It may describe certain technical functionalities of the component, or record certain parameters during its operation (including maintenance times, etc.). But the contents may also be general technical data, documents such as operating instructions or information about disposal or recycling.

On the one hand, the asset administration shell is a formal description of the asset in the form of a (technology-independent) metadata information model with various sub-models. The latter summarise various functional aspects of an Industry 4.0 component. They describe all relevant information and functionalities of a certain object, from its features, properties or capabilities to certain variables or parameters through to specific states and measuring data. As a rule, an AAS always comprises several sub-models.

On the other hand, the content of the asset administration shell and its specific form must be defined. For this purpose, domain-specific templates for sub-models are used to identify and document the asset. On the basis of universal basic sub-models used on many Industry 4.0 objects (such as catalogue data), users can also develop the required sub-models themselves.

Properties of asset administration shells

1. Machine readability

The contents of an AAS are designed first and foremost for machine-to-machine communication. For this reason, information (features and values) must be clearly defined using a classification system. The preferred classification system for contents is ECLASS Version 12.x or higher. However, other classification systems such as eTIM are also permissible.

2. Active/variable vs. static content

For asset administration shells, or AAS, a distinction is made between active and static content.

Active content can largely be found on products equipped with their own processors, internal storage and interfaces. An example of this is a process sensor, which can generate measured values for internal processing and communication. In this case, an asset administration shell may be embedded in the sensor, for example. The sensor continually transmits the measured values to the asset administration shell. This may also be designed to independently communicate with other asset administration shells as part of the industrial internet of things (IIoT).

Static content is often found on simple non-networked products that do not generally have communication interfaces. Circuit breakers are good examples of such assets. While asset administration shells for circuit breakers may exist, the circuit breaker cannot influence any data within the shell.

3. Type vs. instance asset administration shells

Asset administration shells are further divided into type and instance shells.

Type shells (also known as digital threads) contain the most broad characteristics or descriptions of a product or a product line and always depict the most current information. They are used extensively in digital engineering, although they do not represent the digital twin of a real (manufactured) object or asset.

An instance shell, however, is the actual digital twin of an asset. It is unique to the real manufactured product and contains, among other things, the serial number and product information used to create the digital product passport already referred to in this article. It contains information that was current at the time of manufacturing (e.g. the firmware version). Should changes occur later in the product's lifecycle, these must be noted in the instance asset administration shell. Every product with a serial number receives its own instance asset administration shell.

Storing and sharing AAS

There are many different ways to store AAS or share them among the partners involved. In accordance with the basic principle of I4.0, the administration shells should be available to call up within a networked production system. For this reason, storage locations in a cloud and/or in an instance are the most important use cases. Asset administration shells stored in a cloud can be accessed or read by machines via a programming interface or API (application programming interface).

Access to administration shells is obtained, for example, through a digital nameplate according to IEC 61406. This printed nameplate contains a 2D data matrix code, QR tag or RFID tag that links to an instance AAS in the cloud.

Summary: Asset administration shells at a glance

Concluding this brief introduction to asset administration shells are a few points taken from a presentation by the "Plattform Industrie 4.0" initiative.

"An asset administration shell...

• integrates an object into an Industry 4.0 communication network.
• grants controlled access to all information about the object.
• is a standardised and secure communication interface.
• integrates passive assets (without communication interfaces), e.g. via QR codes.
• is accessible within the network and uniquely identifies the asset.

As explained in this article, the AAS can also

• contain active/variable or static information,
• be stored in the object (asset) or in the cloud.

We have implemented the concept of the asset administration shell with static data together with digital nameplates on our platform for you. You can access the type and instance asset administration shells for R. STAHL products in our cloud repository. We offer crucial added value for users for six applications from the product lifecycle in particular. You can find more details here.

We have summarised some information on the connection between Industry 4.0 and security for you on the following pages.

Our team of experts is happy to help should you need any further advice on the these topics. Please use the contact form on this page to contact us.