Topological Optimization of Piezoelectric Energy Harvesting Devices for Improved Electromechanical Efficiency and Frequency Range

The development of energy harvesting devices with piezoelectric transducers has been widely studied in the last decade. Most of previous studies considered a resonant cantilever beam with an attached tip mass and focused on the proper modeling of the cantilever device, design and optimization of electric harvesting circuit and nonlinear amplification of resonant vibration amplitude. However, few studies focused on the optimization of the piezoelectric material distribution as a technique to improve the energy harvesting efficiency. This work presents some results on the topological optimization of the piezoelectric layer bonded to a sliding-free plate (base excitation) connected to an electric circuit. This is done using an electromechanical finite element model for laminated piezoelectric plates combined to a genetic algorithm based optimization. The model fully represents the coupling between base structure, piezoelectric layers and circuits. Electric circuit parameters and tip mass value are optimized simultaneously to guarantee best operating conditions for each topology. Additionally, an inductance is considered in parallel with the harvesting circuit impedance as a means to improve the frequency range of the device. Results indicate that topology optimization of the active layers may increase the harvesting efficiency in terms of harvested energy per unit mass of the device. It was also observed that the inclusion of resonant circuits may improve the amount of harvested energy and the effective frequency range of the device.