Systems of Digital Twins and Physical Systems: Interoperability, Decentralization, and Mobility in Robotic Applications

Whereas digital twins are receiving an increasing attention, their implementation has been predominated by monolithic and static solutions. A resulting issue is the lack of a modular integration and seamless interplay of digital twins when it comes to adapt and support varying industrial and societal applications. Another drawback arises from limited services that digital twins can provide as the physical system is extended with new components and/or separated from constituting parts, giving rise to a metamorphosic system of systems. Furthermore, the respective mobility of physical systems and citizens assumed to interact with them via their digital surrogates is hardly transformed into industrial and societal opportunities, such as a pervasive and itinerant human-robot-interaction ($\pi$-HRC). Within the scope of our Metarobotics framework that propels $\pi$-HRC, we address these challenges by leveraging on the OPCUA standard to develop portable data connectors that move with and give access to the data source, which is the associated physical system. Our Raspberry-Pi driven connector encapsulates a digital twin of the corresponding system and its offered services to capture the loose coupling and decentralization of systems of systems even remotely and in motion. Each data connector semantically interoperates with any OPC-UA capable system and device via wireless communication. This opens up new opportunities for different monitoring (and control) modalities of large scale systems whose physical or/and virtual constituting subsystems are distributed across distinct geographical locations in the industrial and societal realm. We apply our framework to a mobile multi-arm robotic system with edge-computing capabilities and demonstrate the performance of its monitoring functionality from the cabin of a moving train in city traffics in practice. We provide experimental measurements results and highlight the usefulness and effectiveness of our approach.