Control method for boosting generated energy in vibration-based harvesting

Abstract

In this paper, we propose a new control method to boost electrical energy. Vibration energy harvesting extracts electrical energy from structural vibrations. To boost the harvested energy, synchronized switching harvesting on inductor (SSHI) technique has been proposed and developed. With a harvesting circuit including an inductor and a switch, SSHI technique controls electric current by switching action. The technique effectively converts the mechanical energy of structural vibration to electrical energy, but at the same time, it suppresses the amplitude of mechanical vibration. Because the voltage generated by a piezoelectric transducer depends on the vibrational amplitude, the decrease in the vibrational amplitude leads to the reduction in the generated voltage. As a result, the harvested energy is decreased. We confirm that the vibrational amplitude and the harvested energy are decreased with SSHI. To solve this critical problem, we devise a new control strategy to boost the harvested energy. The original SSHI conducts switching action at every peaks of vibrational displacement. In order to avoid the suppression of vibration, our control strategy is designed to temporarily stop the switching action. The structure is excited to vibrate by a vibration exciter. While switching action is stopped, the vibrational amplitude will be recovered from the suppressed amplitude by the excitation force, which makes the vibrational amplitude as high as possible. Accordingly, the harvested energy will increase. We experimentally demonstrate that our control strategy holds back only 12.6% reduction of the vibrational amplitude, while the original SSHI causes as much as 76.4% reduction. The piezoelectric voltage is up to 2.9 times greater than that with the original SSHI. Experimental results show that the proposed control strategy can generate 8.4 times larger electrical energy than the original SSHI.

Keywords

• boosting energy
• vibration-based harvesting
• energy harvesting
• piezoelectric
• sshi