Modeling and Electrical Characterization of a Cantilever Beam for Mechanical Energy Harvesting

Electrical energy scavenged from ambient vibrations enables to supply low-power electronic devices. The most common structures used in vibration energy harvesting are piezoelectric unimorph and bimorph cantilever beams. The modeling of such multilayer structures is widely studied using analytical or numerical approaches. To get a predictive model for designing and optimizing cantilever-based mechanical energy harvesters, an accurate set of piezoelectric material parameters is required. We have developed an original approach to identify material parameters of a thinned-bulk piezoelectric layer based on a 1D analytical model and a 3D finite element (FE) model. The pursued goal is to build 3D FE models for the design of cantilever-based mechanical energy harvesters. In this paper, we present experimental and numerical investigations on the electromechanical behaviors of unimorph and bimorph structures in free-free mechanical boundary conditions. For each structure, the electrical impedance response in frequency domain given by FE simulation is compared to experimental results. A good agreement between computational and experimental results is observed with less than 2% variation on the resonance frequencies. This proves the effectiveness of our FE modeling tool in predicting the electromechanical behavior of unimorph and bimorph structures.