With the dawn of Industry 4.0, the focus of modern manufacturing has changed and advanced work spaces in which there is a greater man-machine collaboration are replacing conventional stations, with humans taking centre stage.
One of the fundamental elements of Industry 4.0 is the operator, and the concept of the “Operator 4.0” (Romero, Bernus et al., 2016) has been defined as the smart and skilled operators of the future, who are assisted by automated systems, which provide a sustainable relief of physical and mental stress, therefore enabling the operators to utilize and develop their creative, innovative and improvisational skills. The different dimensions are indicated below:
- Virtual and augmented operator: The workers must undergo regular training to acquire and update the skills required by these new procedures. The use of mixed reality technology (virtual reality and augmented reality) make it possible for training and guidance to be adapted to changing circumstances.
- Social and collaborative operators: The workers possess considerable tacit knowledge about good working practices and problem solving. Making this knowledge visible and accessible by using social media-based tools has the potential to complement the guidance provided by official documentation and formal practices. Being able to connect this knowledge to the manufacturing environment context will further facilitate the possibility to share and access information about good practices, warnings and observations.
- Super-strong operator: As well as the aforementioned technologies that make it possible for the workplace to be improved by mentally supporting operators during the execution of everyday tasks, another aspect that must be taken into consideration are the ways in which physical support can be provided. For tasks that cannot yet be automated through the use of collaborative robots, the use of wearable devices such as exoskeleton devices make it possible for the operator’s musculoskeletal load to be reduced.
- “One-of-a-kind operator”: The adaptive interaction solutions improve the workflow and help the workers to understand and develop their skills. An adaptable manufacturing system should provide operators with personalised and contextual assistance, which will enable them to execute the task at hand in a more efficient and effective manner.
- Healthy and happy operator: In future factories, the operators are empowered to take responsibility for their own work, wellbeing and skill development. Several studies have supported the idea that employee satisfaction has a positive influence on their productivity. The use of wearables, such as wristbands or other systems, can monitor certain operator parameters.
Operator 4.0 topology 
The use of new technical enablers focused on HMI technologies (Human Machine Interaction) such as augmented and virtual reality, robotics and wearable devices, or the use of physical assistance devices such as exoskeleton devices offer promising ways in which the aforementioned concepts can be materialised. Below you will find a short definition of each of these technologies:
- Augmented reality: In the bibliography you will find different definitions of augmented reality, however, the most commonly accepted definition is the one proposed by Azuma, who defined it as a system that combines the real and virtual world by using specific displays, which allow the user to see the information from both environments in a combined manner; it is interactive, in real time and shows the information in 3D.
The use of augmented reality in the VW factories 
- Virtual reality: This is a computer-generated and artificial re-creation or simulation of a real and specific situation or environment. While virtual reality offers a digital re-creation of a real environment, augmented reality allows for the superimposition of virtual elements in the real world.
The use of augmented and virtual reality in BMW’s productive processes 
- Exoskeletons: You will find several definitions of exoskeletons in the bibliography, however, the most commonly accepted definition is the one proposed by Looze et al., who defined it as an external mechanical structure that can be used to improve a person’s physical capacity and these can be classified as “active” or “passive. An active exoskeleton is comprised of one or more electric, hydraulic or pneumatic actuators that are used to augment human strength and help their articulations, whereas a passive exoskeleton is used to store energy in forward bending work.
Study on exoskeletons in the Groupe PSA plant in Vigo 
- David Romero, Peter Bernus, Ovidiu Noran, Johan Stahre. The Operator 4.0: Human Cyber-Physical System & Adaptive Automation Towards Human-Automation Symbiosis Work Systems. ResearchGate [Internet]. 2016 [Sep 2016]. Available at: https://www.researchgate.net/publication/309609379_The_Operator_40_Human_Cyber-Physical_Systems_Adaptive_Automation_Towards_Human-Automation_Symbiosis_Work_Systems
- Ronald T. Azuma. A Survey of Augmented Reality. unc.edu [Internet]. 1997 [August 1997]. Available at: https://www.cs.unc.edu/~azuma/ARpresence.pdf
- De Looze, MP, Bosch, T, Krause, F, Stadler, KS and O’Sullivan, LW. Exoskeletons for industrial application and their potential effects on physical workload. Ergonomics Journal. [Internet]. 2016 [May 2016]. Available at: https://pubmed.ncbi.nlm.nih.gov/26444053/
-  ACE Factories – Human Centred Factories: Human-centred factories from theory to industrial practice. Lessons learned and recommendations. [Internet]. Available at: http://ace-factories.eu/wp-content/uploads/ACE-Factories-White-Paper.pdf
-  Automotive Manufacturing Solutions: Augmented reality technology assists Volkswagen to remodel Chattanooga production lines. [Internet]. Available at: https://www.automotivemanufacturingsolutions.com/assembly/augmented-reality-technology-assists-volkswagen-to-remodel-chattanooga-production-lines/40351.article
-  Engine Technology International: BMW applies VR and AR technology to production technologies. [Internet]. Available at: https://www.enginetechnologyinternational.com/features/bmw-applies-vr-and-ar-technology-to-production-processes.html
-  CTAG: CTAG collaborates in an exoskeleton study in conjunction with Groupe PSA and MUTUA UNIVERSAL. [Internet]. Available at: https://ctag.com/ctag-colabora-en-un-estudio-de-exoesqueletos-junto-a-groupe-psa-y-mutua-universal/