## 1 Introduction
### The Importance of Human-Robot Collaboration (HRC)  
The aim of industrial robotics is to enable efficient performance repeatedly and accurately [9]. Currently, assembly lines have important requirements related to adaptability, mainly due to the rapid rate at which new products are introduced to the market, as well as changing technologies. The current trends in industry reflect a shift from \"mass-production\" to \"mass-customization\". Products now come with numerous variants or upgrades and a much shorter product lifetime. This imposes a challenge regarding flexibility and adaptability on the manufacturing process, a challenge for which human-robot collaboration is an attractive arrangement [10]. Companies have traditionally relied on robots with in-built capabilities and limited flexibility. However, this level of flexibility is not enough to match the current market's demands [11]. While traditional robot systems provide high payload capabilities and repeatability, they then suffer from limited flexibility and dexterity [12]. Thus, human-robot collaboration is a suitable arrangement to leverage the unique capabilities of both humans and robots for increased efficiency and quality in industrial scenarios. The recent trend of automation and data exchange, known as Industry 4.0, also supports the use of collaborative systems in industry. The aim of Industry 4.0 is to achieve efficiency, cost reduction, and increased productivity by means of integrated automation. This aim highlights the need for flexible and interoperable systems, including intelligent decision-making software and robots that can be quickly, safely, and intuitively operated by humans [13].  
Industries are increasingly relying on HRC arrangements, both from an engineering perspective and from a socio-economic standpoint. While the manufacturing industry is a significant source of employment, it has been reported that most jobs offered by this sector may remain unfilled. This is attributed to a shortage of workers with the relevant technological and technical skills [14]. HRC is, therefore, a promising alternative, which makes up for the skill gap, still requires human operators, and may be more attractive to the younger generation. Additionally, robotic systems result in higher competitiveness with countries with cheap labor systems and increase trust in the company's technological aptitude. Collaborative systems also alleviate the ergonomic burden on human workers, resulting in an improved work environment and a reduction in occupational injuries. This makes environments that include both robots and human labores more attractive to interested partners, customers, and the public [15]. Modern technologies of intuitive systems such as augmented reality, walkthrough programming, and programming by demonstration are all simple methods to operate collaborative robots, unlike the advanced technical expertise necessary to operate traditional robotic systems [13].  
Currently, collaborative robotic solutions are attractive even to small- and medium-sized companies since such systems are more affordable, compact, and easy to use compared with traditional robotic systems. Traditionally, factory floors have had strict divisions of labor, with robots confined to strict safety cages far from humans. Collaborative robots overcome this division of labor, allowing humans and robots to work closely together. In doing so, the advantages of strength and automation of the robot are combined with the flexibility and intuitive nature of the human [12; 13]. Evidently, there are numerous advantages to collaborative robotic systems, including economic, social, and ergonomic improvements to traditional systems. However, to harness the full benefits of such systems, companies should adhere to the appropriate safety standards to ensure optimal operation. These will be discussed in the following section.