マンジ型振動子を利用したオートパラメトリック励振発電素子

抄録

In order to achieve miniaturization and decrease in the acceleration threshold in the autoparametric excitation harvester, we developed a Manji-shaped (Buddhist cross) oscillator and proposed use of the seismic mass attached on the Manji-shaped oscillator. We developed analytic solution by simplifying the motion of equation and qualitatively discuss the important parameters in the autoparametric excitation harvester as well. This study considers the autoparametric excitation harvester, in which the harvesting cantilever is mounted on the doubly-clamped oscillator and the directions of the displacement are normal to each other. The theory indicates that the acceleration threshold can be minimized, when the eigenfrequency for the doubly-clamped oscillator is twice that of the harvesting cantilever. In addition, the increase in the displacement for the doubly-clamped oscillator and in the degree of bending of the harvesting cantilever can help induce the autoparametric excitation easier. The Manji-shaped oscillator was fabricated through photolithography, followed by the wet-etching. The Manji-shaped oscillator can significantly reduce the harvester's volume by compacting the clamp and the beam area. The overall harvester's volume including the frame is 56×56×68 mm³. Thanks to the seismic mass attached on the center of the Manji-shaped spring, the acceleration threshold, which is required to induce the autoparametric excitation, is as low as 0.12G. The output power of our piezoelectric autoparametric excitation harvester is 1.3 mW at the applied acceleration of 0.3G and the frequency of 56.2 Hz.