Wearable sensors networks for safety applications in industrial scenarios

Industrial contexts, and in particular the port areas, are very complex systems to be monitored and controlled due to the combined presence of vehicles and people. The port areas are the gateway between navigation and terrestrial transportation and are of great importance in transport logistics. Unfortunately, the management of port areas is quite complex because the safety of the workers must be always assured. Therefore, in such a context, a centralized control system for the monitoring and the prevention of risks is of particular importance. In this thesis, a real-time control system for the monitoring of people and vehicles in industrial areas is proposed. The proposed system is based on the Internet of Things paradigm, i.e. a network of “things” (such as sensors, tag RFID, actuators etc.) which can communicate and interact with each other within a shared IP addressing range, in order to share data and contribute to the management and development of advanced applications. Specifically, the thesis is focused on the design of a wearable sensors network based on RFID technology, and specifically on WISP sensors, for assuring the safety of the workers. In this network, wearable devices that can be inserted directly on the textile have been selected. Differently from conventional sensors, wearable sensors ensure a higher level of comfort, and provide higher electromagnetic performance. Furthermore, textile materials are easily available. Microstrips are good candidates for these applications because they mainly radiate perpendicularly to the planar structure, and their ground plane allows a good shielding on the body tissues. Therefore, I have designed specific antennas for RFID, that unlike the classical microstrip antennas have the radiating surface composed of several "side by side" conductive "threads of textile". Since the microwave model does not allow the design of an antenna with these characteristics with a good approximation, a specific microwave model for coupled lines has been designed. With this model, the specific antenna for RFID has been designed, with Jeans as substrate. The particular antenna’s substrate allows direct integration into garments, but since the wearable antennas are placed very close to the human body, biological issues which may arise on the human body from the use of these sensors have been analysed. The Specific Absorption Rate (SAR) has been considered and simulations have been conducted for evaluating the effects on the human body, and especially on the head, when irradiated with the electromagnetic waves generated by the wearable antenna realized with different materials. Dosimetric effects have been evaluated in function of the distance from the body, in order to define a safe distance for placing the antenna on the human body. The SAR has been evaluated also for full patches with different textile substrates, whose surface is larger than that of the proposed model of coupled lines. Therefore, if the SAR values evaluated for the full patch are satisfying, the SAR values for the model of coupled lines will surely be acceptable.