In his science-fiction novel Snow Crash, Neal Stephenson introduced the word "metaverse" in 1992. The novel describes a networked world, "Metaverse," parallel to the real world. Meta means "transcendence," and verse refers to "universe". Later, Roblox, a sandbox game platform, became the first metaverse concept game. Since then, the concept and articles about the "metaverse" have appeared in many media reports, attracting the attention of people from all walks of life, even government departments, and creating the "meta-universe" phenomenon.

But the metaverse isn't just a place for gamers and kids playing Roblox. That is why we keep hearing about serious companies establishing a presence and services there, including maintenance services. To some extent, companies make the jump just because they don't want to miss out, even though the metaverse for industry and especially for maintenance is still in its infancy.

Indeed, the metaverse is only emerging and is years, even decades, from maturity. Even the naming conventions for this virtual world still need to be settled. We are not sure if we will have "the" metaverse, "a" metaverse, "many metaverses", or a "multiverse" as a "pool of parallel metaverses". However, even at this early stage, the value that can be obtained from the metaverse is close at hand. The buzz and hype may be exaggerated, but that doesn't mean we can't obtain value from the components and parts that go into it.

With the development of technology, the fantasies described in Snow Crash have gradually become more real, making it easier for people to cross the physical distance of the real world and connect, improving the immersive experience. In the metaverse, people perform their daily activities using avatars representing their "real" or imaginary selves. Simply stated, a virtual space becomes the real world for an alternative life with avatars or digital profiles participating in events, sometimes for private and sometimes for professional purposes – with possible economic implications.

Metaverse is still evolving, but its components are ready for use. These components include the technologies, tools, and systems these virtual worlds are built on and accessed through and the underlying concepts that support the new experiences. Some of these technologies have been around for some time, and the concepts are being applied in active metaverse platforms.

The immersive technologies

Realizing immersive experience requires hard and soft technologies, plus a pool of services. Two dominant technologies underlie the metaverse: augmented reality and virtual reality.

Augmented reality adds a digital graphic element to an existing, physical, real-world through the use of technologies such as glasses, lenses, or smartphones. In effect, it superimposes information on the natural environment. This technology has been especially popular in maintenance, where superimposed information for technicians has facilitated quicker repairs and increased the maintainability of assets. Lifelogging is a subclass of augmentation of the inner world where smart devices are used to record daily lives on the Internet. Examples of lifelogging are the social networks we use daily for professional or private reasons, such as Facebook, LinkedIn, or Instagram. Lifelogging is promising for maintenance, as machines connected in a machine-to-machine (M2M) environment are expected to deliver new services based on the social networking of assets in an unattended manner.

Virtual reality is a virtual online 3D reality, with avatars and communication tools simulating the inner world. The avatar can be personalized. Even though virtual reality's cultural, physical, and social characteristics are different from reality, the avatar, like a real person, can communicate with other entities and achieve goals. Online video games are a well-known use of virtual reality. But virtual reality also applies to industrial settings. For example, in the virtual commissioning of new plants or assets, technicians can recreate the future shop floor, and correct or adapt as required, thus avoiding costly trial and error actions. A subclass of virtuality mirrors worlds that are virtualizations or simulations of the real world. The authentic appearance, information, and structure are transferred to a virtual space to carry out activities via the Internet or mobile applications. Well-known examples are Google Maps and Google Earth.

There is a lot of debate about whether AR or VR will dominate the market. The truth is that each has its unique value. Each enables users to experience and interact with the digital worlds that comprise the metaverse and the avatars that inhabit them.

Each offers adaptability for different maintenance scenarios since using specific gadgets on the shop floor is impossible. Sometimes it is possible to use a PC or mobile device. Still, the immersion and physical interaction offered by a head-mounted display and hand-tracking controllers are much more natural and engaging than those of a keyboard, mouse, or games controller. Moreover, a remote maintenance action may require an immersive experience rather than a standard inspection, and augmented information provided by a device might be enough. But it is the convergence of these technologies and concepts that is truly the game changer when it comes to leveraging the metaverse.

While current headsets can be hot and heavy, the technology is advancing rapidly, and a new generation of slimmer and lighter devices suggests the beginning of a more comfortable way to access the metaverse. VR and AR offer different experiences, with VR fully immersing users and AR layering digital items over the real world. Use cases that demand a fully immersive experience will benefit more from VR use, whereas others that depend on interacting with the natural world will necessitate AR. Neither is better than the other, and neither is "wrong."

The metaverse is a location where the real world is augmented, connected, and replicated with virtual reality, and, as such, it can be considered another world. For the digital generation, the metaverse is and will be a space where they spend part of their daily lives. The Covid-19 pandemic accelerated this trend with widespread isolation measures. The changes caused by the pandemic also had maintenance implications; Covid-19 limited maintenance inspections and interventions. Consequently, many activities moved from only being offline to also becoming virtual. In other words, the metaverse is not only a place offering escape but where people will live part of their lives. In the maintenance context, it means there is a better ability to safeguard the robustness and resilience of assets by providing virtual assistance and skipping costly actions to inspect remote and unattended equipment. The connection with the metaverse is facilitated by new technologies that allow us to be part of the online world 24 hours a day, all the time, and everywhere. The benefits for the maintenance sector are evident in terms of health monitoring, support and training of technicians, and remote troubleshooting.

Consequently, maintenance as a service is attracting interest in the metaverse, with researchers examining the potential of the virtual world for detecting and predicting failures and providing maintenance support.

Digital Twins and Cyber-Physical Systems as avatars of our assets

Thanks to Industry 4.0 and the upcoming Industry 5.0, a dramatic technological transformation linking the physical world to the digital space has been accomplished. Digital twins and cyber-physical systems (CPS) define how a physical system integrates sensors, communication, computing, and control in a large-scale cyberinfrastructure. Digital twin technology is vital in boosting this convergence. This technology permits global industries to establish digital copies of their processes and assets to optimize maintenance and performance. Digital twin and CPSs technologies provide virtual representations, digital replicas, or copies of products, but also people, in the form of avatars. We could say the avatars of humans in the metaverse will interact with digital twins of the assets that are, in fact, avatars of assets.

CPS are systems linking networked products and operations. Digital twins are engineering systems that drive new abilities to design, operate, maintain, and create new services to maximize value. Therefore, the digital twin of an asset is expressed as a virtual (digital) profile of a physical thing or process's current and past state, providing the elements and dynamics of how the replicated system performs and degrades using CPS as a backbone.

Digital twins, as avatars of our products, add value to the industrial metaverse and beyond from the perspective of extended reality, with platforms for managing and analyzing data and experiencing the immersive interactions of avatars with digital products. Indeed, the key aspect of the maintenance metaverse is that digital twins of assets with different maturity levels will be transferred to the metaverse and become the avatars of these assets, ready to interact with the avatars of the maintenance crew.

Metaverse platforms for immersive remote monitoring and control of intelligent industrial applications are challenging but achievable with appropriate gadgets. An industrial metaverse will include detailed digital twin models equivalent to full real-world assets where Industrial Internet of Things (IIoT) data and 3D digital models link digital and physical worlds. The merging of digital and physical object interactions that is already underway gives credibility to the concept of a metaverse as a viable future reality.

Digital twins are a fundamental requirement for realizing the industrial metaverse, when assets are perceived from multidimensional perspectives to initiate new maintenance frameworks, such as remote monitoring, troubleshooting, and training new workers through an interactive simulation.

On the one hand, for monitoring purposes, integrating digital twin technology with real-world data-related technologies will enable the creation of advanced simulation algorithms that could anticipate how processes and products will perform and degrade. Such algorithms must integrate IIoT data, Industrial AI, data analytics, and domain knowledge to improve output. Given the advancements in AI and Big Data technologies, the virtual models (digital twins) can become a staple in modern engineering, thwarting costly asset failures, eliminating the sophisticated testing of products and processes, and fostering efficient predictive and monitoring capabilities of systems.

On the other hand, using metaverse and digital twin-enabled solutions as training and remote troubleshooting platform will help in testing systems and obtaining feedback. Based on the feedback, the system could be optimized, and the experimentation could be repeated.

At the initial stage of the testing, since a digital platform or a clone of the machines is used, the wear and tear of the intelligent industrial machines and gadgets will be safeguarded. Further, based on the learning from the digital simulation platforms, testing could be done on the physical industrial machines in industrial settings, thus achieving real virtual commissioning with a high success rate. This immersive and virtual experience will allow maintainers to collaborate with experts and trainers from remote locations.

In summary, considering digital twins as a tool to monitor dynamic changes in systems is crucial for maintenance applications in the industrial metaverse. Metaverse solutions are essential for remote maintenance managers and workforce groups who can use digitally cloned models for testing, monitoring, intervention, and training. In this way, the metaverse will become a powerful platform for maintainers and beyond.

Its role in assisting virtual teams in gaining access to or control over digital clones is also being considered as a means of promoting new business models in the field of maintenance as a service; this includes remote troubleshooting and assistance, but it also includes innovative alterations in the digital clones based on ongoing failures, problems, and maintenance actions, thus promoting new product development and reliability growth.

Metaverse and maintenance actions

There are clear relations between the metaverse and the prevention and mitigation of failure. The metaverse can certainly be adopted for diagnostic and repair support with satisfying results. Maintenance 4.0 has already adopted and adapted various innovative technologies, such as IIoT, CPS, cloud, fog, Big data Analytics, machine learning, blockchain, and Industrial AI.

Immersive technologies are becoming increasingly important. The disruptions they bring to performing maintenance will include the ability to monitor and interact remotely with a large population of assets and educate those involved in maintenance activities. Digital innovations can be adopted as an alternative maintenance service model; indeed, the possibility of creating avatars allows consultations and personalized actions. In the metaverse, maintainers could "consult" in a 3D virtual workshop using remote services and devices, such as wearable sensors and smartphone applications, monitor the health status of assets, and once they have a "diagnosis", perform maintenance intervention using haptic sensors and robotic actuators.

The potential for incorporating monitoring devices into asset health programs is enormous. Different devices can be adapted to remotely monitor asset health conditions, connecting real life with the virtual world. The health of a distant asset can be assessed by IoT sensors, plus a number of virtual sensors, with Industrial AI models within the system adding further physical and expert knowledge. The creation of soft sensors will increase health visibility and improve maintenance criteria. With this information, both real and virtually created, maintenance crews will evaluate asset performance and damage propagation, comparing, in real-time, their data with the data of other users worldwide. Through real-time monitoring, maintainers can be part of an online community, and being guided by experts worldwide increases the likelihood that they will attend maintenance good practices programs and adopt world-class decisions.

Moreover, these monitoring devices will allow assets to be fully present in the metaverse, 24/7. Importantly, monitoring health parameters around the clock will facilitate prompt prevention or intervention, helping service providers improve maintenance security. Along with monitoring, in the metaverse, a virtual and AI-based avatar or agent may provide personalized feedback and support, and, in this way, maintenance interventions could become more effective.

Finally, an avatar that can act as a "virtual doctor/nurse" may be able to directly monitor and interact with the asset, providing individualized care and treatment but also supervising and monitoring, in real time, the "patient's" evolution after maintenance or repair actions. In this way, the metaverse can serve as a transitional stage before maintenance providers tackle real-world problems. In the metaverse, they can accompany assets into specific individualized environments, thus enhancing the efficacy of maintenance programs and actions. Beyond maintenance, however, virtual care models with group support programs could be a valid intervention in real-world health problems; in this context, remote virtual nursing care with robotic end-user delivery units could be helpful.

Prof. Diego Galar, Ramin Karim, and Uday Kumar from the University of Luleå, Sweden

References
Galar, D., Kumar, U., & Seneviratne, D. (2020). Robots, Drones, UAVs and UGVs for Operation and Maintenance. CRC Press.
Karim, R., Galar, D., & Kumar, U. (2021). AI Factory: Theories, Applications and Case Studies.
Galar, D., & Kumar, U. (2017). eMaintenance: Essential electronic tools for efficiency. Academic Press.
Galar, D., Daponte, P., & Kumar, U. (2019). Handbook of Industry 4.0 and SMART Systems. CRC Press.