Development of an electromagnetic-based low-frequency vibration energy harvesting system for a fatigue crack monitoring wireless sensor

Abstract

This dissertation presents a developed low-frequency vibration energy harvesting (VEH) system, which consists of a vibration energy harvester and energy harvesting circuits, and is then integrated in a structural monitoring wireless sensor. The uniqueness in the dissertation lies in (1) development of high performance VEH system for low-frequency (below 10 Hz) bridge vibration, (2) realization of an entire processes of VEH for bridge applications, and (3) numerical and experimental validations of the developed VEH system. Specifically, an electromagnetic-based vibration energy harvester is developed with two degrees-of-freedom (DOFs) and frequency tunable designs. By virtue of the designs, the developed vibration energy harvester shows better performance than other conventional vibration energy harvesters. An active diode-based AC-DC converter and a boost-up converter with varying clock frequency constitute the two-stage energy harvesting circuits. A field test conducted in Yeondae Bridge shows that a peak power of 43.09 mW and an average power of 4.09 mW were produced by the developed vibration energy harvester. The developed energy harvesting circuits exhibited up to 50 % conversion efficiency at an input voltage of 200 mV or above. In addition, the developed vibration energy harvester and energy harvesting circuits are integrated along with a battery in a wireless sensor for fatigue crack detection and failure warning installed in Yeongjong Grand Bridge. It is estimated that the developed VEH system can harness 128.04 J for 3 weeks. Finally, the self-sufficient operation of the wireless sensor would be possible when the duty cycle is prolonged to 24 weeks.