Power density ratio optimization of bimorph piezocomposite energy harvesters using a Multidisciplinary Design Feasible method

A design optimization involving mechanical and electrical considerations is proposed with the aim of improving the performance of bimorph piezocomposite energy harvesters for micro-electromechanical systems. Maximization of the power density ratio of the transducer was achieved using a Multidisciplinary Design Feasible method accounting for several design variables and subjected to operational and physical constraints. The present numerical approach shows that superior performance can be obtained via multidisciplinary design in comparison to designing the mechanical and electrical parts separately. A composite cantilever beam type of harvester formed by a brass shim covered by PZT-5A piezoelectric layers was considered. Predictions of tip displacement, voltage and power output were carried out using an analytical model of the harvester, based on Euler-Bernoulli theory and an energy approach. Finite element analysis of the harvester was also performed for the purpose of model verification and analysis of fidelity issues. The results of the implemented optimization procedure provided valuable design relations concerning the dependence of the aspect ratio of the transducer on the operating frequency, as well as regarding the optimal thickness ratio to be selected for the active and substrate layers.