# The Role of Maintenance Operator in Industrial Manufacturing Systems: Research Topics and Trends
## 5 Discussions and Research Trends
Animprovement in company performance depends, in part, on an optimized management of human resources, and in maintenance, this issue is studied from several points of view. Indeed, in maintenance scheduling activity, the problem of human factors is an interesting investigation area faced by several studies. Positive effects in the improving maintenance program were obtained by including human constraints (such as availability, competences level, and error) in a maintenance-scheduling problem. Production scheduling generally requires a controlling agent of the production process, whereas maintenance activities require specified agents that are characterized by skill levels and qualifications ([51]), allowing them, or not, a good execution of the maintenance activities. Maintenance operators' proficiency and competency mapping plays a key role in the human resource assignment problem. The measurement of their performances has become essential. The major aspect, discussed in some papers, is assessing the current competencies of an employee. Different models, framework, and tools for evaluating operators' qualification level, through the classification of variables affecting human performance, have been proposed. The outcomes demonstrated the importance of measuring competences to gain high levels of business performance. **TEND 3**: Finally, the review results showed an increasing interest concerning the emerging supporting technologies in maintenance activities. Industry 4.0 is a current trend in the manufacturing field, based on the concept of \"smart factory\". Industry 4.0 provides several enabling technologies for supporting the maintenance operator in performing a task or in maintenance training. VR is a key technology for industrial training used in the digital factory. VR allows for the creation of an environment through the use of computer technology to develop the condition of an interactive 3D world in which objects have a sense of spatial presence [95]. The new training method enables the operator to interact with the prospective work object even without the presence of the training object, giving him the chance to train at any desired place. Studies showed VR technology can improve maintenance system training by reducing the time for training and by enhancing cognitive skills and motor skills for performing a task. Another relationship between the investigation field with enabling technology of industry 4.0 is represented by Augmented Reality (AR) technology. Several studies showed the application of AR supporting the human maintenance operation through a mobile or wearable device to plan and perform maintenance tasks efficiently and in easier way, increasing the productivity of the system. The experimental research of some papers demonstrated how enabling technologies can help human resources to reduce time and errors of maintenance tasks. The current research trends in this field aims to reduce maintenance costs through the enhancement of the operator's performance at work. In particular, technologies supporting operators aim to reduce the error rate during the execution of maintenance activity, the time of completion task and to improve the quality of work; another trend aims at reducing time and cost for the training by providing supports for instructions that are more accessible and easier to understand also for an unskilled operator. Figure 9 shows the relationship of the different topics obtained from the LDA approach with the identified trends, as discussed above. Summarizing some topics univocally belong to one of the identified trends. Other topics, instead, are distributed among more than one identified trend, since addressed and investigated research subjects belonging to different areas.