Investigation of networked SSHI configurations for plate-based piezoelectric energy harvesting

Vibration-based energy harvesting has received significant interest over the past two decades to generate electrical power to be used in small electrical devices and components mostly powered with conventional batteries to reduce maintenance cost and eliminate battery disposal. Among the existing transduction mechanisms, piezoelectric transducers are in the interest of the researchers as they have large power densities. In the majority of the studies about harvesting applications, the piezoelectric energy harvesters are in the form of cantilevered beams, with one or two layers of piezoelectric materials, which are known as unimorph configuration and bimorph configuration, respectively. As an alternative to the cantilever beam energy harvesters, patch-based piezoelectric energy harvesters are more efficient and easier to implement on plate-like structures to convert the vibrational energy of the host structure to electrical energy. Piezo-patch energy harvesters attached to plate-like structures can be used to extract multimodal vibrational energy in automotive, aerospace, and marine applications. The alternating current obtained from energy harvesting should be transformed into a more stable (DC) form for practical applications. For most of these transformations, a full wave standard AC-DC rectifier circuits are used. To improve the output power, researchers have studied several circuits, including synchronized switch harvesting on inductor (SSHI) circuits. For each piezo patch, SSHI circuits can boost the harvested power compared to standard rectifier harvesting circuits. However, the effect of using different configurations of the SSHI networks for multiple piezo patches on plate structures have not yet been understood. This study aims to assess the performance of the networked SSHI configurations compared to networked rectifier configurations and investigate the optimum configurations for energy harvesting purposes. In this study, three piezo patches are bonded to an aluminum host plate and connected to single and/or multiple energy harvesting circuits. The electromechanical system's equivalent circuit model (ECM) is developed from the experimentally validated analytical model and utilized in an electronic circuit simulation software LTspice. Four different case studies of single/ multiple rectifiers and SSHI circuits are considered. The first two cases include a single rectifier/SSHI circuit, while the other two include separate rectifier/SSHI circuits for each patch. The performances of each configuration are evaluated under harmonic excitation in terms of peak power outputs, and the optimal load resistances are obtained for each configuration. Based on the experimental findings, the best configuration is determined and verified by the ECM results. The results show that by using respective SSHIs, the power output can be improved by preventing charge cancellation despite the cost of increased diode loss. This study contributes to our understanding of optimal energy harvesting techniques by investigating the effectiveness of networked SSHI configurations for multiple piezo patches on plate structures.