Modeling and experiment of a multiple-DOF piezoelectric energy harvester

Vibration energy harvesters have been usually designed as single-degree-of-freedom (1DOF) systems. The fact that such harvesters are only efficient near sole resonance limits their applicability in frequency-variant and random vibration scenarios. In this paper, a novel multiple-DOF piezoelectric energy harvester model (PEHM) is developed, which comprises a primary mass and n parasitic masses. The parasitic masses are independent of each other but attached to the primary mass. The piezoelectric element is placed between the primary mass and the base for energy generation. First, a 2DOF model is analyzed and characterized. Through parametric analysis, it is found that with a slight increase of the overall weight to the original 1DOF harvester (without parasitic masses), two close and effective peaks or one effective peak with significantly enhanced magnitude can be achieved in the power response. Subsequently, the 2DOF model is generalized to an n-DOF model and its analytical solution is derived. This solution provides a convenient tool for parametric study and design of a multiple-DOF piezoelectric energy harvester (PEH). Useful multimodal energy harvesting can be achieved with a slight increase of the overall weight. Finally, a prototype of the proposed multiple-DOF model is devised for proof of concept.