Modelling and optimisation of a force amplification energy harvester

Abstract

A flexure frame mechanism is a device historically used to amplify the displacement of an actuator with limited travel, such as a piezoelectric stack actuator. Conversely, these mechanisms may be used as a generator to amplify the force applied to piezoelectric transducers. This in turn can greatly increase the harvested power. Previous studies have used a variety of methods to analyse the amplification factor of a flexure frame mechanism operating as an actuator in displacement mode, as opposed to a generator in force amplification mode. The effects on the performance of such a device when operating in force amplification mode are not as well understood. In this study, an analysis of the force amplification of a flexure frame mechanism is conducted. A model of the force amplification factor based on the material properties and geometry of the device is developed for use as an optimisation and design tool. The analytical findings are compared against finite element analysis simulation and experimental results for validation. The effect of the stiffness of the central piezoelectric stack and the maximum stresses developed in the frame are determined to be critical parameters in determining the effectiveness of the mechanism as an energy harvester.