Design and Implementation of Wireless Sensor Systems for Industry 4.0 Applications

This doctoral thesis was funded by the Crosslab project of the University of Pisa. The development of sensing systems for Industry 4.0 was the main focus of the work carried out. The main findings from the conducted research include the development of radio frequency and microwave sensors compatible with Industry 4.0 and Internet of Things (IoT) applications. The presented sensors rely on transducing the physical parameter of interest, i.e. the measurand, by relating to a change in the response of the sensor, namely a change in the reflection coefficient of the sensitive part of the sensor. The monitored output from these sensors was the magnitude of the real part of the input impedance; a quantity closely related to the amount of reflected power. The developed sensors were presented in Industrial Automation Applications: Wireless Distance Sensor suitable for integration with production lines (ex: conveyor belts/lines) for object counting, tracking, or size detection. Another presented sensor in the same area of application was dedicated for guidance of Autonomously Guided Vehicles (AGVs), in particular, path-following AGVs in industrial automation context, ex: for material handling in a warehouse or factory. Another field of application that has been explored was the monitoring of vital signs. A wearable sensor dedicated to the monitoring of the respiration rate was designed, fabricated, and characterized in this doctoral thesis. The sensor relies on the displacement of the human body during respiration to produce a signal that is related to the respiration of the human subject wearing the sensor tag. This wearable sensor provided very accurate results when compared with a reference ground-truth sensor, and has been characterized by conducting and analysing a large number of measurement data sets. The last topic in this doctoral thesis was dedicated to the design of a novel low-cost RF reader for the proposed sensors. The goal of this reader is to replace the Vector Network Analyzer (VNA) which is the measurement instrument typically used with this kind of sensors. The replacement of the VNA, typically expensive and bulky devices, offers several advantages such as: significant cost reduction and potential compatibility with planar or wearable systems. The reader is based on a hybrid 180 degrees coupler that separates the input signal from the reflected signal and finally uses a gain/phase detector board to measure the magnitude and phase of the reflection coefficient.