A tunable resonant electromagnetic vibration energy harvester and power management system for wireless sensor networks

Vibration energy harvesters (VEHs) convert vibrational energy into electrical energy and can be used to power wireless sensor networks (WSNs) for machine condition monitoring. However, there are challenges in the development of practical VEHs, including matching the resonant frequency, maximizing the converted energy, and managing power storage and delivery for WSN nodes. This paper presents a tunable resonant electromagnetic VEH transducer and power management system to address these challenges. The transducer is composed of cylindrical magnets, an enclosed back iron, an internal coil, and a circular flat spring. The resonant frequency is tunable by rotating a support structure to vary the length of the spring and therefore the spring constant. This tuning architecture allows for a wide resonant frequency range and a compact enclosure. The transducer was modeled, simulated, and tested experimentally. In testing, the transducer demonstrated a tunable resonant frequency range of 93 Hz, from 45 to 138 Hz. The transducer was then tuned to 60 Hz, and independent tests were performed in vibrations of 60 Hz and 0.3 g RMS acceleration. The transducer generated 3.93 mW over an optimal resistive load. In separate integrated system tests, the power management system delivered 1.76 mW to the battery and 1.56 mW to the regulated supply. The presented system and investigation contribute to the development of practical VEH technology for powering WSN nodes.