Two-Stage Wideband Energy Harvester Driven by Multimode Coupled Vibration

This study develops a piezoelectric vibratory energy harvester intended for wideband operation at low frequencies. The harvester features a two-stage vibratory structure. The first stage picks up ambient low-frequency vibration and excites the second stage to vibrate at its resonant frequency, thereby realizing frequency upconversion and improving power-generation capability. The first stage is designed as a multimode resonator to adapt to a wide frequency band by multimode vibration coupling. Finite element simulation and lumped-element modeling indicate that the multimode coupled vibration at the first stage can excite the second stage into wideband resonance that well adapts the electric power generation to the wideband ambient vibrations. The micro harvesters are fabricated, with the testing results validating the design concept. The harvester can operate under acceleration amplitude of 1g and frequency from 10 to 30 Hz. A peak power of 24.56 mu W and a maximum average power of 3.62 mu W are achieved at 1g and 20 Hz. The harvester also exhibits power generating capability under excitation of the vibration from a running bus, where a peak power of 6.89 mu W is generated.