Ubiquitous monitoring of distributed infrastructures

Reliable operation is critical for modern industrial, civil, and commercial distributed infrastructures. This dissertation focuses on the design of novel monitoring technologies for underground power cable systems that provide real-time monitoring, low-cost, high-measurement resolution, and comprehensive system coverage. The ubiquitous monitoring approach described in this dissertation consists of two complementary parts: mobile robots and passive RFID-enhanced sensor networks. This new research field poses several significant design and engineering challenges: (a) the mobile robot must be small enough to fit the space and agile enough to negotiate the obstacles it encounters along its path; (b) only non-destructive, miniature, low-power, and high-accuracy sensing technologies are best suited to fulfill its functions; (c) passive RFID-enhanced sensor nodes must harvest sufficient power to operate within an expected range. A novel robotic prototype for monitoring of power cables was designed, fabricated, and tested in both laboratory and field conditions. Its hardware consists of a driving mechanism, a distributed embedded control board, and a signal acquisition and processing system. Four types of miniature non-destructive sensors were integrated in the robot. These sensors can detect the most common causes of failures, including over-heating, partial discharge activities, natural aging status of insulation material, and the presence of water trees. This dissertation presents the operating principles and the experimental results obtained with these sensors. The theoretical estimations of the power scavenging capability and the loop antenna design guidelines for inductively coupled HF RFID systems were derived and verified with experiments. An adaptive impedance matching algorithm was proposed to improve the energy scavenging for the over-coupling scenario. A novel RF front-end IC for the passive UHF RFID tag was designed, based on the 0.18 μm TSMC18RF process. This fully functional IC can drive an equivalent 200 kΩ load at 1.6 V with -12 dBm input power, resist large input power variations, and provide a demodulated rail-to-rail digital output signal. The dissertation concludes that the use of ubiquitous monitoring in distributed infrastructures is economically efficient and technically feasible. In the future, such developed technology could also be employed in other industrial systems.