Abstract
The interest of the literature in the last few years around the theme of Digital Twins (DT) and its connection with the pillars of Industry 4.0 (I 4.0) paradigm, in particular relating with Virtual Reality (VR) and Augmented Reality (AR) technologies has strongly grown. As a matter of fact, since 2018 it can be noticed a steady increase in publications that relates to these technologies, especially DT and VR. However, even if the body of the literature is rich in journal papers, conference papers and book chapters, it lacks specific literature reviews that connects these technologies. Therefore, the main aim of this paper is to provide a clear overview of the applications of VR and AR concerning the brand-new concept of Digital Twins. In doing so, this study conducts a bibliometric review carried out with a Systematic Literature Network Analysis (SLNA) on the relationship between VR, AR and DTs. Firstly, by analysing the literature, this article describes the main contributions to the research on VR and AR-related DT applications. Secondly, this paper aims at identifying the main topics to which DTs have been related when matched with VR and AR concepts, and therefore to identify the importance of these technologies on DTs applications. Finally, the paper provides an analysis of the past, present and future trends of DT applications in the literature when related to VR and AR. In doing so, a new visual analysis and representation of keywords trend in time, based on the co-word network analysis typical of the SLNA, is presented, i.e. the Keyword Trend Detection (KTD). The study leads to two main conclusions. The first is related to contributions branches identification. Indeed, two main branches of contributions have been identified; the first is related to the concept of virtualization of manufacturing resources, while the second is focused on the applications of DT and VR. Secondly, as a result of the application of keyword clustering techniques, this research identified five clusters of research streams, i.e., AR-, Robotics-, Virtual-, I 4.0 pillars-and DT-related clusters.