Plucking and linear-to-rotary hybrid harvester for low-amplitude vibrations of high-speed railway with an innovative three-step amplification mechanism

Abstract

By harvesting the pervasive vibration energy, self-powered wireless sensor network (WSN) installed along the track can play an important role in structure health monitoring of high-speed railway. However, a considerable part of vibration energy of the rail is difficult to be harvested due to the characteristics of ultra-low frequency, small amplitude and large load. A hybrid frequency up-conversion energy harvester is designed and optimized in this paper aiming to address this critical problem. By utilization of a unique three-step amplification design for reducing inefficient transmission due to the possible gap of gear or ball-screw systems, high-efficient energy harvesting is realized for the small-amplitude excitation with both electromagnetic and piezoelectric conversion structures. The experiment results verify that the gapless amplification achieved by the flexible hinge structure as the first-step mechanism is effective for solving the gap issue. Compared with harvesters without the flexible hinges, the power is 250% higher under an excitation of low frequency (5 Hz) and ultra-small amplitude (0.3 mm). Moreover, based on the hybrid energy harvesting mechanism, more appreciable energy is obtained by introducing the plucking piezoelectric structure in addition to the electromagnetic unit.