Harvesting strategy to increase electrical energy for piezoelectric active harvesting

In this paper, we present control strategies to increase electrical energy for active harvesting. Vibrational energy harvesting extracts electrical energy from structural vibration. To increase the harvested energy, synchronized switch harvesting on inductor (SSHI) technique was proposed. With the switching action, SSHI effectively converts mechanical energy into electrical energy. We experimentally confirm that the vibrational amplitude and the harvested energy are decreased with SSHI. To solve this critical problem, we devise control strategies that are SCVS (Switching Considering Vibration Suppression) and ASCVS (Adaptive SCVS) to increase the harvested energy. Original SSHI conducts switching action at every peak of vibrational displacement. Our control strategies are designed to temporarily stop the switching action. The vibrating structure is excited to vibrate by a vibration shaker. While switching action is stopped, vibrational amplitude will be recovered from the suppressed amplitude by excitation force. The proposed control strategies can maintain the vibrational amplitude as high as possible. Accordingly, the harvested energy increases. We experimentally demonstrate that the proposed strategies increase the harvested energy. Experimental results show that the stored energy with our techniques is up to 10.5 times greater than that with the original SSHI technique. Moreover, ASCVS (Adaptive SCVS) is shown to be more flexible to increase harvested energy in various vibration conditions.