Passive antenna sensor design through multi-physics modeling, simulation, and optimization
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This dissertation develops passive (battery-free) wireless strain sensing techniques for low-cost structural health monitoring (SHM). Passive wireless strain sensing has obvious advantages among SHM technologies in that the sensors require neither cable nor external power supply for operation. However, current numerical approaches for modeling and designing passive antenna sensors are oftentimes inefficient and inaccurate. In this study, a partially air-filled cavity modeling and an inverse power iteration method with Rayleigh quotient (IPIRQ) are proposed to significantly improve computational speed of strain sensing simulation. Optimization frameworks are proposed for identifying accurate mechanical and electromagnetic parameter values of an antenna sensor through finite element model updating using experimental measurements. In addition, a multi-objective optimization approach is formulated to maximize sensor performance such as strain sensitivity and antenna gain. Finally, in order to overcome the limit of radiofrequency identification (RFID) antenna sensors, a frequency doubling technology is investigated. To achieve close deployment of multiple frequency doubling antenna sensors, a wireless switching mechanism is designed and implemented. Performance of the frequency doubling antenna sensors with wireless switching is experimentally validated.