# Augmented Reality-Based Framework Supporting Visual Inspection for Automotive Industry
## 3 The Proposed Cognitive System for Inspection
### Cognitive Assistant System Conception and Design
#### 3.2.1 MQTT-Based Data Transmission  
Throughout the line production, the vehicle is carried on and investigated by a set of sensors indicating its state of conformity. To avoid direct access to the main Industry DataBase (DB), ensuring data security, the IIoT platform has been implemented for data flow. In the final line production, the vehicle must be inspected by the operator based on  
Figure 3: Proposed data transmission architecture for the automotive industry.  
Figure 2: Screen from the final inspection station of the industry under study.  
the list of active errors which are provided by the automotive Industry DB, and which need to be fixed. The next step consists of displaying this list of errors in a UI. To do that, the MQTT protocol is adopted for the data transmission between the IIoT platform and all the other components. MQTT protocol is considered one of the principal messaging protocols of IIoT thanks to its rapidity during the machine-to-machine data transmission, which is a much-needed requirement in the manufacturing environment. Contrary to the web-based solution, which is a client-server-based communication, MQTT relies on the publish-subscribe concept allowing several clients to connect to a unique server that is called a broker [26]. These clients would be able to publish and/or subscribe to a specific topic via connection to an MQTT broker. Besides, the broker is considered the administrator for the publishing/subscribing technique. Its key role consists of receiving, filtering, and emitting messages to the correspondent subscribing clients [27]. The clients in our scenario are both the cognitive assistant system and the IIoT platform which can connect, subscribe, and publish in the broker. Having received the list of errors, collected from the sensors, and stored in the main Industry DB, the IIoT platform would be able to connect to the MQTT broker as well as publish this list into it. On the other part, the cognitive assistant system connects to the same broker and subscribes to the topic of active errors. These latter are handled by the operator and at the final process, the proposed system would be able to send the list of solved errors to the same broker. Thereafter, the IIoT platform subscribes to the topic related to the list of controls solved by the operator and sends the final list to be stored in the Manufacturing Execution Systems (MES). Indeed, MES is a real-time-based system supporting the concept of Industry 4.0, location sensing, mobile, and advanced analytics to identify most likely probable problems as soon as possible [28]. The main goal behind the adoption of such a system in Industry 4.0 is ensuring high performance and warranting the rapidity facing the quick change of costumer's demands [29]. In our context, the used MES is designed by critical manufacturing [28] based in Portugal having the principle features of decentralization and vertically and horizontally way of integration.  
The following sub-section details the way of data visualization and management from the operator side.