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In recent years, great advances in understanding the opportunities for nonlinear vibration energy harvesting systems have been achieved giving attention to either the structural or electrical subsystems. Yet, a notable disconnect appears in the knowledge on optimal means to integrate nonlinear energy harvesting structures with effective nonlinear rectifying and power management circuits for practical applications. Motivated to fill this knowledge gap, this research employs impedance principles to investigate power optimization strategies for a nonlinear vibration energy harvester interfaced with a bridge rectifier and a buck-boost converter. The frequency and amplitude dependence of the internal impedance of the harvester structure challenges the conventional impedance matching concepts. Instead, a system-level optimization strategy is established and validated through simulations and experiments. Through careful studies, the means to optimize the electrical power with partial information of the electrical load is revealed and verified in comparison to the full analysis. These results suggest that future study and implementation of optimal nonlinear energy harvesting systems may find effective guidance through power flow concepts built on linear theories despite the presence of nonlinearities in structures and circuits.

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With an ever-growing Internet-of-things, vibration energy harvesting has attracted broad attention to replace consumable batteries to power the many microelectronic devices. To this end, an energy harvester must deliver the required power to an electrical load over a long time horizon. Yet, design practices for energy harvesters often report strategies based on maximizing output voltage and wide frequency range of operation, which is not directly related to performance-robust functioning. Motivated to provide valuable insight to practical development of vibration energy harvesters, this research develops an analytical modeling framework and optimization technique to guide attention to piezoelectric laminated energy harvesting cantilevers with balanced and robust performance characteristics. The model is numerically and experimentally validated to confirm the efficacy of the optimization outcomes. The results indicate that laminated trapezoidal beam shapes with monostable configuration are the best solution to broaden the frequency range of enhanced dynamic behavior, minimize strain at the clamped beam end, and maximize the output voltage in a rectifier circuit. The results also find that the selection of tip mass may not be highly influential for the overall performance so long as the beam shape, beam length, and placement of nonlinearity-induced magnets are appropriately chosen.