Electromechanical Modeling of a Multifunctional Energy Harvesting Wing Spar

Abstract

A recent advance in the eld of energy harvesting is the development of multifunctional energy harvesting systems. Multifunctional material systems combine several functionalities in a single device in order to increase performance while limiting mass and volume. In energy harvesting systems, multifunctionality can be achieved by combining energy generation capabilities with energy storage ability and/or load bearing ability in a single composite device. An application that can bene t from a multifunctional energy harvesting approach is the powering of remote, low-power sensors on unmanned aerial vehicles (UAVs). The added weight or volume of conventional harvesting designs can hinder the ight performance of UAVs, thus a multifunctional solution where the energy harvesting system can be designed into the aircraft and used as a structural member can provide increased performance over the traditional design. The authors have recently proposed the concept of multifunctional self-charging structures containing piezoelectric layers for energy generation and thinlm battery layers for energy storage. Integration of these multifunctional structures into the wing spar of a UAV presents the ability to not only harvest and store energy, but support structural loading in the wing. In this paper, the electromechanical modeling of a wing spar with embedded energy harvesting and storage ability is investigated. A coupled electromechanical model based on the assumed modes method is developed to predict the vibration response and voltage response of a cantilevered wing spar excited under harmonic base excitation. Experiments are performed on a representative wing spar with embedded self-charging structures and the results are used to verify the electromechanical model. The electrical performance of the representative spar is also investigated by examining the variation of the peak voltage, current, and electrical power with load resistance for the fundamental short-circuit and open-circuit resonant frequencies of the device.