# Augmented Reality in a Lean Workplace at Smart Factories: A Case Study
## 2 Literature Review
### Augmented Reality and Human Augmentation
This emerging technology has enabled the move from traditional paper-instructions to the utilization of 3D visualization procedures in recent years, which carries a significant potential regarding the elimination of waste caused by delays and human errors [65; 66], as well as the reduction in training and operating times and the fostering of working conditions, quality, productivity and efficiency [67; 68]. A recent review of the literature on this topic [69] summarizes 36 cases of AR technology applications in in-house logistics that are using superimposed virtual information in order to provide information to workers and enhance their sight sense, mostly using HMD and HHD. Furthermore, WWD equipped with barcode and QR code scanning technology are commonly used for order- picking and can reduce the operation times and the amount of equipment needed to perform these tasks, freeing the workers' hands and speeding package scanning and inventory control, when compared with HHD [70]. Additionally, when it comes to AR wearable devices, it's important to consider the ergonomic conditions and understand if it is comfortable and safe for workers that will use it during the working  
Figure 1: Types of AR [59]. day [71]. WWD and AAR enable a hands-free operation that allows the employee to relieve the physical workload and manipulate the packages with both hands [72]. The implementation of new techniques and the instruction of workers on the necessary skills can be time-consuming and may impede the effectiveness of logistics operations. However, the use of AR technology during the training period can result in employees with the necessary knowledge to complete complex and challenging tasks, and this can boost productivity and shorten their learning curve [73]. Moreover, AR has the potential to enhance workers' cognitive capabilities, provide feedback and data for safety measures, or even alert the operators regarding an immediate hazardous situation or danger in real-time [74]. AR solutions can also improve the quality of life for individuals with disabilities and the elderly, making the workforce more inclusive and sustainable., These solutions help to reduce disparities in the workplace [64], holding a set of benefits to assist workers with disabilities [75] In addition, they enhance physical capabilities, through the usage of exoskeletons to improve working conditions and allow operators to perform their tasks longer and lift heavier weights, while reducing the physical workload, injuries, accidents and risk factors [58]. Human augmentation techniques rely on the use of technologies that are able to augment human actions, senses, capabilities and cognition, allowing humans to perceive the real environment in a new and enhanced way. Based on augmenting technologies, relevant information is provided to operators, in order to enhance human life and allow new Human-Machine Interface solutions [64]. This approach is centred on the AR users and based on a human-centered real world merged with an information world [62]. Operator 4.0 is a concept that has emerged in Industry 4.0 context and can be understood as an Augmented Operator that performs collaborative work with machines and robots, being enabled by CPS and advanced technologies [76]. AR is a critical enabling technology for improving information transfer between the digital world and smart operators in the physical world [77]. The term Operator 4.0 refers to smart and skilled operators, assisted and augmented by systems that enable a reduced physical and cognitive workload during task performance, allowing them to be more creative and innovative, fostering continuous improvement without compromising productivity [76]. Therefore, the Augmented Operator paradigm is enabling the engagement and empowerment of workers [78], giving people more time to learn, think and innovate. To take advantage of what Industry 4.0 has to offer and successfully utilize emerging technologies such as AR, businesses must develop human-centred production systems that put the needs of workers first.