# An Approach Based on VR to Design Industrial Human-Robot Collaborative Workstations
## 1 Introduction  
In modern factories, humans and robots frequently coexist in a common space, where robots complement the operator's capabilities, while humans take care of the most delicate tasks (e.g., high precision tasks, visual quality check, decision-making, strategic process control) [1]. human-robot interaction (HRI) refers to all those processes where humans and robots work together, sharing the same space, time, and resources [2]. More specifically, human-robot collaboration (HRC) takes place in a specific collaborative shop floor, where robots and humans can perform tasks concurrently, also having direct, physical contact with each other [3]. Multiple workstations where machines and humans collaborate with each other are frequently created in order to accelerate industrial processes, by benefiting from both robotic and human work. This practice is becoming pretty common in highly automated assembly processes. In this context, shared human-robot activities should be carefully designed to properly execute collaborative tasks in the most efficient and effective way, considering not only system productivity, but also the physical and cognitive workload of the human operator, and exploring the effects of collaboration on system usability and worker's perceived cognitive workload and visual attention [4]. Moreover, it is noteworthy that in this scenario operators' responsibilities and workload further increase due to high production rates, complex task demand, time pressure, as well as monitoring and control jobs [5]. As aconsequence, the new human-robot collaborative work can bring to stressful working conditions for human operators, causing physical stress and cognitive tensions [6]. Nevertheless, as a major advantage, the availability of human-robot collaborative solutions allows to combine the advantages of robots, such as high accuracy, speed, and repeatability, with the flexibility and cognitive skills of human workers. As a result, such solutions have become important tools to face growing needs of flexible production and rapidly changing market demands. Such phenomena, framed in the concept of Industry 4.0, affect any size organizations. On the one side, small and medium-sized enterprises (SMEs) are directly affected, since one of their strengths is that they can accommodate specific market requests allowing for high product customization, small batches production and one-piece flow. SMEs benefit from their intrinsic agility and limited inertia in decision and operational processes to accommodate dynamically changing market requests. This represents a market niche where SMEs still hold a significant competitive advantage over bigger companies and, as such, it should be protected and enhanced. Nevertheless, SMEs often do not have a solid management infrastructure to help accommodating flexible production in an ordered manner [7]. On the other side, as regards bigger companies, the automation trend introduced by Industry 4.0 is to achieve high flexibility also for them: this requirement is partially conflicting with their bulky organization and layered structure. Thus, to achieve the goal of flexibility, while preserving the capability to accommodate constantly changing market requests, proper technological solutions are needed to reorganize workstations as promptly as possible at the beginning of new production cycles [8]. A good solution in this regard is represented by digital tools, offering effective visualization and simulation of such collaborative processes, before their realization [9]. Moreover, recent advances in Information and Communication Technology (ICT) have brought to an increased maturity of also X-Reality (XR) technologies, such as Virtual Reality (VR) and Augmented Reality (AR), showing promising opportunities for researchers and industries to simulate new types of HRI and HRC [10].