Effect of revolute joint mechanism on the performance of cantilever piezoelectric energy harvester

In this paper, we present a novel method to improve the electric performance of cantilever piezoelectric energy harvesters (PEHs), i.e. by embedding the revolute joint mechanism. The harvester is usually fastened onto a host structure via one edge of the substrate. The embedment substitutes part of the edge, forming a discontinuous boundary condition. The joint mechanism greatly reduces the stiffness and damping factor of the harvester and thus increases the resonant intensity. This leads to larger deformation of the piezoelectric component and higher voltage output. We investigated mainly four cases in terms of the length of the joint by modeling for numerical solutions, and by fabricating prototypes for experimental validation. Both numerical and experimental results of the hinged cases, which agree with each other quite well, indicate that the output voltage of the PEH is up to 2.94 times as high as that of the counterpart case (full clamped or non-hinged). Furthermore, the output power is escalated by more than 670%. With no additional mass or volume added into the structure, the power density is improved by the same magnitude. In terms of applications, the hinged harvester displays much better charging performance with a higher charging rate and saturation voltage. This study can be of great significance to evidently boost the electric yields of cantilever PEHs. (paper)