Digital twins are virtual entities that are linked to real-world entities. Twins mirror their real counterparts and consist of features that are selected to serve the underlying use cases. Over the past decade, digital twins rose from an engineering curiosity to a concept praised by consulting agencies, offered by corporations, and pursued by governmental agencies. Digital twins are expected to bridge the gap between digital and physical worlds.
This dissertation set out to build machine design-focused digital twins for industrial products, specifically for an industrial overhead crane. However, during the work, it turned out that the existing tools and techniques did not allow the scalability required to create a twin for each manufactured product, suggesting that a more ground-up research approach was required. Hence, the latter part of the dissertation focused on initiating the development of fundamental digital twin technologies.
The four main results are a feature-based digital twin framework, a case study on practical digital twin development, preliminary digital twin document specification as a method for describing digital twins, and Twinbase as server software for distributing digital twin documents. 1) The framework presents a conceptual approach for building digital twins, consisting of features and connecting software blocks to build modular digital twins. 2) The case study describes lessons learned from developing a multi-component digital twin for an industrial crane in multiple teams and organizations. 3) A digital twin document enables the integration of twin components and acts as a master metadata source for a digital twin. 4) The open-source server software Twinbase allows twin owners to publish digital twin documents as effortlessly as possible, allowing rapid development cycles and innate collaboration.
The developed technologies will accelerate the creation and standardization of scalable digital twin entities. As a synthesis of the results, the dissertation introduces the Digital Twin Web (DTW) as an initiative for building a global network of digital twins. In the network, each digital twin is represented by a digital twin document. The structure of DTW is analogous to the World Wide Web (WWW), consisting of servers and clients and leveraging open specifications. Key differences are the direct relation to the real world and readability for both humans and machines. Standardization of the digital twin document is seen as an imperative topic for future research. Other topics for standardization were identified as well, for example defining a transfer protocol for twin documents.
During the digital twin development, user-friendly Application Programming Interfaces (APIs) proved valuable resources, and also open-source software and open standards supported the development.