# 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
[PERSON] [66] proposed a new real-time AR based tool to help operators during disassembly operations, providing augmented instructions to efficiently perform maintenance activities. An integrated predictive maintenance system was proposed by [PERSON] [67], which demonstrated that, through the application of mixed visualization interfaces, which assist operators during maintenance activities, downtime is reduced, and the reliability of the maintenance operations increases. AR technologies and mobile devices were used in Reference [69] to support maintenance services in industrial environments [69]. Specifically, 3D visual instructions are represented as in the real world through AR and directly visible on a mobile device. In addition, the framework introduced the possibility to monitor the operator's work from a remote location. The study in Reference [70] presented a prototype of an interface for maintenance operators, using Gamification techniques for motivating the user, and AR and HUD to display information in an HMD device. A novel AR maintenance assistant system was described by [PERSON] [72] enabling operators to navigate on instructions, while they are wearing gloves and handling light tools. An integrated production and maintenance schedule, supported by AR technology and real-time machine monitoring, was presented in Reference [74]. As a step towards Industry 4.0, the proposed system, through the integration of data from different systems, demonstrates the great benefits that can be obtained in the production system, as well as in maintenance activities. The real-time communication between the planning and monitoring system, as well as the use of AR technology, allow the maintenance operator to work efficiently and consequently increase the overall performance of the system. Instead, Reference [76] discussed how Computer-mediated Reality (CMR) and Artificial Intelligence (AI) can be implemented in the energetic sector, and how they can reduce human errors, improve hazard identification, and reinforce procedure adherence. Personal Augmented Reality Reference System (PARRS) is a suite of computer-mediated reality applications that minimize human error through the digitization of manual procedures and providing real-time monitoring of possible dangers. Papers [58; 59; 64; 68; 71; 76; 77] belonging to this topic were all focussed on the impact assessment of technologies use on system performance. In particular, the main purpose was to evaluate the positive effects of these technologies on human performance as well as system performance, both for supporting operators during maintenance tasks and maintenance training. Some compared performances with traditional support with respect to technologies-based, others instead measure KPIs using technology and user experience. For example, Reference [71] conducted a study that demonstrated the advantages of using virtual-reality-based systems for training automotive assembly tasks. Sixty participants were randomly assigned to different training experiences to learn car service procedures. The results showed that virtual-trained participants, after training, can remember significantly better the correct execution of the steps with respect to video-trained trainees. The paper in Reference [58] presented a mobile assistance system for service and maintenance personnel in industrial facilities. An experiment was designed to measure three characteristics of industrial usability in compliance with EN ISO 9241-110: effectiveness, efficiency, and satisfaction. Reference [77] presented the effectiveness evaluation of providing technical in structions with spatial AR prototype with respect to conventional paper-based instructions. The study conducted an experiment with 16 participants to measure user task performance (in terms of completion times and error rates) and to gather subjective evaluations.