# Smart Interactive Technologies in the Human-Centric Factory 5.0: A Survey
## 2 Smart Interactive Technologies in the Human-Centric Smart Factory
### Large Displays
#### 2.2.2 The Smart Factory Context  
Smart factories are proving increasingly capable of absorbing and proposing solutions from a wide range of disciplines. The introduction of gestural interfaces and the widespread use of large screens is a case in point. Gestural interfaces, similarly to other technologies and approaches in the HCI field, are part of the _physical layer_ in [39]'s classification of technologies for the smart factory. **Applications: 3D object manipulation and task browsing. ** Ref. [40] investigated the interaction between people and 3D objects shown on public displays in an urban planning scenario. Participants were asked to perform tasks through spontaneously produced hand-gestures and phone-gestures. The process led to the definition of two sets of user-definedgestures. Although the proposed study limited its investigations to the area of urban planning, similar studies which identify sets of user-defined gestures can be conducted in various fields, including the industry sector. For example, Ref. [24] proposed the use of large displays in combination with touchless gestural interaction on the shop floor (Figure 1). In the context of a smart industry project, the project consortium developed a smart armband which allows us to detect gestures from movement and muscle biosignals, while a machine learning library allows us to calibrate and recognize task-specific gestures (Figure 2). The definition of an appropriate set of gestures underwent several steps, including a guessability study [23]. The proposed application was tested in small industry specialized in sheet metal fabrication, where welders frequently switch between their workbench and a nearby desktop computer to browse the tasks they have been assigned and visualize 3D models of the final product. Results were generally positive and the participants were favorable to our solution and willing to use it in their everyday work activities. **Tackling usability issues. ** An interesting solution, specifically focusing on the context of smart factories and combining gesture recognition with augmented reality (see Section 2.4) to address usability issues, was given by [41]. To overcome the hard and time-taking learning curves in switching from an industrial device to another, [PERSON]. [41] investigated the development of a universal interaction device, capable of communicating with various field devices and plant modules of an industrial facility via common wireless communication standards. Their aim is the creation of a platform that has one user interface for all purposes, is nonproprietary, and can be designed individually dependent on its owner's requirements. Merging together gestures recognition with augmented reality, they offer intuitive interactions, freeing the operator from the constraints of manipulating hand-held objects. Figure 1: User interacting with a large display via a touchless gestural interface [23; 24]. Figure 2: User testing a smart armband for gestural interaction on the shop floor [23; 24]. 2.2.3. Challenges and Guidelines for Touch and Touchless Interaction with Large Displays in the Smart Factory  
Based on our analysis of the relevant literature, it is apparent that free-form gestural interaction is useful in contexts where touch-based interaction is not possible (e.g., because users wear gloves) or not advisable (e.g., because of hygiene policies). On the other hand, performing gestures might be physically demanding and, especially in the case of touchless interaction, some specific issues may emerge, such as:  
* Unintentional gestures might be misinterpreted by the system as intentional gestures. * Carrying out tasks that require precision through free-form gestures might be problematic. More specifically, [PERSON] and [PERSON] [42] proposed the following guidelines for the design of gestural interaction, based on previous work by [10; 43; 44]. * **Guideline 1: Semantic intuitiveness. ** Gestures should have a clear cognitive association with the semantic functions they perform and the effects they achieve.