## 3 Qualitative Analysis of the Application of AR in Industrial Assistance and Training
### AR Virtual Operation Guide  
AR _virtual assistants_ provide immersive experiences that enhance operators' understanding of complex operations through AR simulations, which create safe and hazard-free environments. This assistance mode has been extensively researched and adapted across various industrial contexts. For instance, [PERSON] et al. [49] proposed an AR virtual assistance guide, while [PERSON] et al. [59] developed support systems for real-time remote  
Figure 3: Distribution of different subcategories of AR use in context of industrial assistance and training. maintenance using AR. [PERSON] et al. [67] introduced an AR maintenance assistant utilising YOLOv5, while [PERSON] et al. [42] employed interactive projections for maintenance tasks. [PERSON] et al. [70] developed an AR application to simplify the mechanical bar-bending process, and [PERSON] et al. [81] proposed an AR-based intelligent predictive maintenance approach for industrial machinery integrated with IoT. AR _interfaces_ have become invaluable tools for enhancing performance in activities such as assembly and process visualisation. Their intuitive and interactive guidance capabilities simplify complex task execution, thereby improving overall efficiency. AR interfaces have been employed in various contexts, including the creation and management of BIM projects [43], providing task assistance based on deep learning and 3D spatial mapping with RGB-D data [55]. Additionally, the use of AR combined with infrared thermography has proven effective for industrial maintenance [72]. Furthermore, a projected AR assistance system for manufacturing with multimodal interaction has been proposed [82]. With regard to the efficacy of AR systems in _assembly performance_, studies by [PERSON] and [PERSON] [58] demonstrate the potential of AR-based assistance in assembly operations. Furthermore, the integration of simulation and AR methodologies has been explored as a means of enhancing manual assembly assistance [51]. More recently, research has highlighted the benefits of AR in improving assembly performance. For instance, AR-assisted object mapping has been shown to facilitate worker assistance and training, significantly improving efficiency and reducing error rates compared to other guidance methods [85]. Other research has addressed real-time occlusion processing for AR assembly assistance systems using monocular imaging [83], the creation of AR-assisted hands-on experiences to enhance assembly line performance [54] and AR systems that facilitate dynamic gesture recognition and prediction [64]. Additionally, deep learning-based techniques have been integrated for recording and managing instructions in AR-assisted assembly [79]. The utilisation of AR for _process visualisation_ facilitates a more lucid and efficacious comprehension of workflows and operations. [PERSON] et al. [80] conducted a qualitative study on the use of mobile remote assistance with AR for the visualisation of industrial processes. [PERSON] et al. [49] put forth a framework to facilitate the implementation of this visualization in the industrial sector. In a similar vein, [PERSON] et al. [51] combined simulation techniques with AR visualisation to enhance operator assistance in industrial manufacturing tasks. _Real-time feedback_ represents a foundational application of AR in industry, facilitating immediate communication and correction during manufacturing, fabrication and assembly processes. In a study by [PERSON] et al. [73], the potential of AR devices for remote support in manufacturing was investigated. In their study, [PERSON] et al. [97] employed AR in the context of task support, utilising advanced techniques such as 3D spatial mapping and RGB-D data, which resulted in fast and accurate real-time responses. [PERSON] et al. [64] developed an AR system for manufacturing assistance, which offered dynamic feedback and gesture prediction. [PERSON] et al. [79] integrated register management into AR-assisted assembly instructions, providing real-time feedback.