Human-in-the-loop in smart manufacturing (H-SM): A review and perspective

Smart manufacturing, also known as Industry 4.0, is a manufacturing paradigm that aims to realize autonomous processes, minimizing human involvement. In the advent of manufacturing-unfriendly situations (e.g., pandemics), it has been learned that the paradigm does not work correctly and has limitations in handling those situations. There is a consensus that humans still play a crucial role in manufacturing, and the ultimate goal of manufacturing is to benefit them. To align with this, the European Commission introduced Industry 5.0, targeting human centricity, sustainability, and resilience. Operator 5.0 has also been presented to improve the physical and cognitive capabilities of shop operators. In contrast, the new concept of human-in-the-loop in smart manufacturing (H-SM), aiming for the involvement of diverse stakeholders, has been recently proposed. In this paper, we introduce the research methodology to elaborate on the current application fields of the H-SM concept. For this, we revisit the existing paradigms and their case studies. Also, we categorize them in terms of different components in H-SM and with respect to different levels of physical and cognitive capabilities and experiences. Then, we identify seven technology clusters and twenty-one key-enabling technologies for the H-SM implementation. It can be concluded the H-SM is well-aligned with human-intervened autonomous manufacturing.