Web-Based Digital Twin asset [ 10 ].
Digital twins can be discrete or composite during their existence [ 2 ]. The discrete digital twin is an entity that generates added value on its own . In a composite digital twin , multiple elements serve a common purpose . Multiple digital twins can further act in a system of digital twins and serve an overarching purpose . In the digital twin , the internal networking of individual components and the external interaction with other twins is thus an important aspect that addressed by suitable communication technologies and interfaces .
In addition to communication , the digital twin consists of further key aspects like data , models and computing . As Fig . 3 already indicates , the aspects are not clearly separable and overlap with each other , all of which influence the digital twin . The data of a digital twin is of different nature and may cover all phases of the product lifecycle . The types of data considered in the following are operational data and simulation data , since these are relevant in the presented context .
Digital Twin
Data Modelling and OPC UA
Fig . 3 : Key aspects of the digital twin .
For the operational data of an asset , the Open Platform Communications Unified Architecture ( OPC UA ) [ 11 ] attains a special position . It is a platform-independent , service-oriented architecture that is being standardized for a wide range of industries . The standard builds on two basic pillars : the transport mechanism and the data modeling . Various communication technologies are available as transports , which differ depending on the approach ( client-server / publishsubscribe ).
But the distinctive feature is the data modeling , which focuses on layer-wise information models . The information models have sub-models for devices in general , as well as extensibility for specific industries and vendor-specific information [ 12 ]. The industry-specific models are the result of collaborations between various companies and organizations and manifest in so-called Companion Specifications . The OPC UA information models represent the state data of the asset . All information and functions are thus available via standardized interfaces , to which the digital twin can also connect [ 10 ].
Simulation and FMI
Another key aspect in the digital twin is simulation [ 13 ] and integration various simulations into a multi-domain simulation chain . The simulation techniques and tools that exist today are mostly designed to be used during product development . On the one hand , these proprietary tools are
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