Topology optimization of 2DOF piezoelectric plate energy harvester under external in-plane force

In this paper, the goal is to design a two degrees of freedom piezoelectric plate energy harvester which can harvest the energy from external in-plane harmonic force coming from different directions. The most challenging problem in this case is the charge cancellation due to combination of tension and compression in different parts of the plate. Therefore, topology optimization method is utilized to find the best possible layout and polarization profile of the piezoelectric plate to maximize the electrical output and to overcome the problem of charge cancellation. To do so, a detailed two dimensional finite element modelling of the piezoelectric material suitable for topology optimization is presented primarily. The topology optimization algorithm is established based on the finite element model to have minimum amount of numerical instabilities. To follow the optimized polarization profile, the electrode in top surface of the piezoelectric plate is separated to two sections that can have potentials with different sign on the same surface. Numerical simulation by COMSOL Multiphysics finite element software and experimental investigation on the fabricated designs demonstrated that the optimized design is highly superior to the classical full plate in terms of produced voltage and electrical power while having less volume of piezoelectric material.