# Virtual Reality Training Application for the Condition-Based Maintenance of Induction Motors
## 3 Theoretical Basis  
### Virtual Reality as a Training Tool  
The incorporation of VR-based environments into training or learning is not intended to replace practical sessions with real equipment. However, it can provide complementary benefits such as greater flexibility through exercises to be completed and repeated as many times as necessary. It also offers the possibility of updating and optimizing training methods based on usage, reducing the cost of purchasing physical tools and materials. To create training experiences, it is first necessary to create a virtual environment that is as similar as possible to the real world. The parameters and values of the objects of study are simulated in this environment. Usually, these environments are generated within a game engine. The most common game engines are Unity and Unreal Engine 4 [1]. In this study, the Unreal Engine 4 game engine was chosen, because it is a powerful game engine that produces high-quality interactive virtual reality experiences and provides native support for virtual reality devices. In addition, this software stands out because of its photorealistic capabilitiesand visual-coding system. It also allows for interfacing with other simulation programs to acquire data in real time and to integrate data from pre-recorded files. Head-mounted displays (HMDs), thanks to the democratization of technology, have become relatively affordable, offering opportunities for implementation in any application scenario [33]. For this development, the HMD HTC Vive Pro Eye was chosen because of its technology that includes a high-quality display and has stable and reliable tracking. It is a virtual reality helmet with six degrees of freedom (6 DOF) and is also equipped with 6 DOF controllers. However, if this HMD stands out for something, it is for offering an eye-tracking module. Exactly what the user is looking at can be tracked, and detailed performance analyses produced. These features make it ideal for use in training applications [34].  
Virtual reality completely changes the way users interact with applications. Immersing users in a virtual world gives them the freedom to experiment and to innovate without any concern about damaging expensive equipment. Thus, in VR, it is possible to experience emergency states and the effects of a misconfiguration and different failures, which are rarely experienced on real equipment, as it can cause damage to the equipment and is often against all health and safety standards. These working conditions also let them work on their own and let them practice outside working hours. In the trainer-user relationship, VR opens a completely different perspective to any classical approach to training. While traditionally the trainee is continuously aware of the trainer's presence, in immersive VR, this presence can become invisible. Thus, the trainer can adopt three strategies of presence. In the first one, the trainer can control an avatar in the VR environment that interacts with the user, closer to the traditional training model. In the second, the trainer can simply visualize the user's behavior in real time, providing audio feedback, thus reducing interference in the learning process. In the third, the trainer can avoid any interaction in real time, analyzing a posteriori the data collected from the sensors on the user's experience. This case is particularly interesting because the user is unaware of the presence of the trainer and behaves in a more natural way, closer to natural behavior in the real environment. However, controllers and gaze tracking sensors collect all their reactions: VR makes it possible to observe how a user behaves with a very high level of detail in a non-invasive way. Finally, it also allows the user to work autonomously and receive immediate feedback on performance [26; 35].