# IoT-Aware Architecture to Guarantee Safety of Maintenance Operators in Industrial Plants
## 5 System Architecture  
Starting from the exposed requirements and inspired by the reported running scenario, the architecture reported in Figure 1 was designed. The architecture is made by different modules that interact with each other through various interfaces.  
The first component is the Tracking Module that is responsible for verifying the position occupied by the operators with respect to both the machinery and also each other single module of the machinery. This autonomous module continuously monitor the presence of operators in the area (identified by specific devices called tags), and interacts with the Backend Server via an Internet connection to: (a) receive the list of the tags associated to each stakeholder, (b) receive the information about the shape/geometry of the machinery and its LOTO points, and (c) exchange the updated status of the position of operators in the monitored areas of the machinery.  
The second component is the Machinery with Increased Safety Measures (MwISM). As anticipated, the maintenance of a single MwISM foresees different consecutive steps and the first one regards its de-energization. Therefore, the MwISM has to interact with the system to let operators, supervisors and administrators be sure that all the de-energizing operations are performed in the right way before the next maintenance steps. In addition, it has also to support the system during the re-energization process and during test phases, if needed. A further element of the MwISM is an innovative separate mode selector enabling a special safety system that guarantees workers safety during maintenance through some specific devices. Thanks to such safety system, the machine is able to: (a) monitor potential stored energy as required by LOTO procedure, e.g., to control the pressure of incoming pressurizedair and send the data to the application supervisor when the smart service selector (see FR2) is on; (b) allow some movements of the machinery components to maintainers without any interaction with the control system of the machine; (c) autonomously control in real time hazardous movements of the machine during service operations. A detailed description of the machinery prototype is outside the scope of the paper and will be omitted for patent pending confidentiality reasons.  
The third component, instead, is the Mobile App. It is an application to be installed on the operators' smartphone and will allow: (a) the receipt of notifications when a new maintenance is assigned to him, (b) view all the maintenances assigned to him, (c) start the de-energization procedure, (d) communicate the successful execution of a specific step of the de-energization procedure, (e) guide the maintenance operator in all the operations, and (f) provide a live technical chat to ask for technical assistance. In addition, as a further security measure, the Mobile App will exploit the Near-Field Communication (NFC) technology to recognize the presence of an operator near the LOTO point in which he is declaring he is when starting a step of the procedure.  
The last component is the Backend Server. It is the core module of the architecture and is responsible for: (a) exposing the necessary REST Application Programming Interfaces (API) to accept inputs from all the other components, (b) store in a database all the data received from the various components, (c) interact with the machinery, (d) expose a dashboard to support the admins and supervisors in their duties (i.e., definition and assignment of maintenance, support the operators through a dedicated chat, etc.), (e) provide an interface for the interaction with the MwISM and, finally, (f) provide support for authentication and authorization.