A DIAGONAL PIEZOELECTRIC ENERGY HARVESTER ON CLAMPED-FREE CONICAL SHELLS

Thin shells are common engineering structures and they have great potentials to harvest more energy from ambient vibrations. The conical shells are forced to vibrate due to the external excitation, and this kinetic energy can be extracted using piezoelectric materials. Recent sensing analyses indicate that a straight piezoelectric patch may output no voltage due to the axisymmetric of conical shells. This study is to address this issue and to overcome the zero output problems. A diagonal piezoelectric patch is proposed for conical energy transduction and harvesting. The diagonal harvester patch shows no symmetry in the longitudinal or circumferential direction for all shell modes. This configuration guarantees the energy output for all natural modes. A mathematic model of the diagonal piezoelectric harvester is given and an open-circuit output voltage of the diagonal energy harvester is derived based on the thin-shell theory and the Donnel-Mushtari-Valsov theory. Then, the distributed modal energy harvesting characteristics of the proposed diagonal piezoelectric conical shell harvester are evaluated in case studies. Numerical results prove that the proposed diagonal piezoelectric energy harvester outputs energy for all known modes. The energy amplitudes vary with the modal shapes. Next the diagonal stripe is divided into several small patches, each patch has separate electrodes. Therefore the output energy amplitudes indicate the energy distribution over the conical harvester surface. The results show that, for each mode with unit modal amplitude, the distribution depends on the mode shape, harvester location, and geometric parameters. The regions with high strain outputs yield higher modal energies.