Coupled electromechanical analysis of MEMS-based energy harvesters integrated with nonlinear power extraction circuits

Application of piezoelectric materials in vibration energy harvesters is expanding rapidly, especially in MEMS-based devices, due to their uncomplicated fabrication processes and reasonable power generation potential. In addition to standard power extraction methods, nonlinear switched techniques with capability of generated power enhancement, are previously developed and extensively applied in energy harvesting using piezoelectric materials. In this article, vibratory behavior of bimorph resonant harvesters coupled to nonlinear circuits of energy harvesting including standard and switched techniques is investigated. An analytical approach employing some perturbation technique, is utilized to derive a closed-form solution for the generated power response of these electromechanically coupled devices in a general case where damping due to energy harvesting cannot be considered as negligible. While linear models lead to significant errors in prediction of harvested power especially in the case of implementing switched techniques, results of the present nonlinear analysis are in a very good agreement with that of numerical solutions. Results indicate that the application of nonlinear switched techniques can lead to peak power enhancement and bandwidth broadening of weakly and moderately coupled devices, respectively, while in the case of strongly coupled devices switched harvesting techniques are not shown to be reasonably efficient.