Reference Framework for Digital Twins within Cyber-Physical Systems

Cyber-Physical Systems (CPSs) represent systems which integrate physical units and processes with computational entities over Internet and allow ubiquitous access of information and services. Although the application of CPSs promise to positively transform many application fields, there are still many open questions and challenges on how to design and realize a CPS. As indicated in the third level of the 5-level CPS architecture, the so-called cyber level, one of the challenges addresses the need for digital twins as high-fidelity mirroring images of CPSs entities. This is a prerequisite to realize the upper levels of the 5-level CPS architecture - the cognition and configuration level. In the scientific literature, the concept of a Digital Twin is introduced as a concrete realization for mirroring physical entities in the virtual world. However, a reference framework for the main building blocks of a Digital Twin framework is missing. This hinders a reuse of best practices and proven solutions for concrete realizations of a Digital Twin. In order to tackle this problem, we have established a reference framework for Digital Twins within a CPS. Our framework specifies the main building blocks of a Digital Twin in terms of structure and interrelations. To achieve this goal, we performed a systematic literature review, where we evaluated existing Digital Twin realizations used in different application domains of CPSs and we applied Grounded Theory and Framework Analysis as underlying methodologies. This reference framework serves a blueprint for developing Digital Twins of physical entities which are part of a CPS.