# The Role of Maintenance Operator in Industrial Manufacturing Systems: Research Topics and Trends
## 4 Paper Content Analysis
### Topic 5 and Topic 8: Virtual and Augmented Reality in Maintenance  
Topic 5 and 8 present a strong correlation, since the studies belonging to these topics discussed on the specific enabling technologies supporting maintenance human resources. Several research studies were interested in the application of augmented reality (Topic 8) and virtual reality (Topic 5), as support tools for human maintenance operations. Indeed, 33% of selected papers showed applications in this field (25 papers). Augmented Reality (AR) was highly considered in industrial maintenance and assembly tasks, whereas Virtual Reality (VR) is the main technology used for maintenance training. Enabling technologies are used for several aims, such as to support operators during a maintenance task performance, train operators for maintenance work, and ensure ergonomic activities, as well as human factors observance in the design phase. 24% of the papers belonging to these topics showed the application of VR for operator's maintenance training; whereas 68% described advantages and applications of enabling technologies supporting the operator during maintenance activities; only one paper [55] showed the evaluation of ergonomics principles through the adoption of AR. Figure 7 provides details on the technologies adopted in the abovementioned papers and related application fields. The distribution over the years of these two topics indicates that the interest in the past years is increasing. In 2017 and 2018, 57.1% and 45.4%, respectively, of the selected papers raised interesting findings on these two topics (Figure 8). Most of the research contributions of the studies belonging to these topics are tools (61.5%). Nine papers [56; 57; 58; 59; 60; 61; 62; 63; 64] presented studies in the interesting field of VR (11% of selected papers). In particular, [PERSON] [56] focused their research on a system for virtual training on collaborative maintenance procedures rather than technical gestures, while [PERSON] [57] addressed the simulation of the haptic feedbacks provided during the manipulation of components and equipment involved during maintenance operations in the aerospace industry: the goal was to improve the overall knowledge and efficiency of the procedures. A new multimodal training system for Industrial Maintenance and Assembly tasks based on Virtual Reality technology-the \"IMA-VR\" system, was proposed by [PERSON] [60], whose aim was to provide an efficient transfer of the skills involved in procedural tasks. Instead, the development of multimedia maintenance manuals based on the synergy between VR, DHM and web-based frameworks was the focus of [PERSON] [62]. Multimedia manuals can reduce maintenance time and cost, improving the quality of working. Finally, the development of multimedia maintenance manuals based on the synergy between VR and DHM was performed in the same manner as the work of [PERSON] [63]. Figure 8: Distribution of the papers belonging to Topic #5 and Topic #8 over the years with respect to the total number of papers. Figure 7: Numbers of papers grouped for technologies and its scope in supporting maintenance operators. [PERSON] [63] analysed the content of the training and then described the parts of a generic operating cycle could be supported by virtual reality. Sixteen papers [55; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77; 78; 79] were focused on AR technology (20% of papers selected). A prototype of a monitor-based AR system is presented in Reference [65], consisting of a motorized controllable camera and a laptop with a headset. The comparison with other tools presenting instructions for maintenance operations showed that the use of this system leads to time savings and lower error rates. The tools effectiveness was measured in two ways: base on the time needed to execute maintenance tasks, and according to the error rate during maintenance intervention.