The effect of geometry on the performance of amplified flexure-guided actuators

Abstract

This study presents an analytical model of a flextensional actuator comprised of a piezoceramic rod or stack transducer integrated into a flexible mechanical structure. It converts and amplifies the longitudinal in-plane strains in the transducer into the out-of-plane bending of metal beams. Two curvilinear beams mounted by means of two hinged links with an offset to a centrally located piezoceramic transducer create a monolithic hinge lever mechanism. The idea behind that solution is to reduce the bending stiffness at the hinges, while maintaining enough axial rigidity of the active beams and obtain greater magnification of the out-of-plane displacement. As the main purpose of this work is to estimate the influence of piezoelectric force on the performance of flextensional actuators of different geometric shapes and mechanical parameters, two transducers have been considered. An analytical model of the actuator has been developed on the basis of the stationary value of the total potential energy principle with the use of the von Karman non-linear strains theory. Moreover, the application of structure prestressing is considered to avoid undesired stretching of the piezoceramic transducer. A vast number of results exhibit the mechanical responses of the actuator of different geometry, initial midspan rise and beam material properties to piezoelectric stimulation. The analytical method described here may be adopted for other types of flextensional actuators. Additionally, a numerical model of flexure-guided transducer is presented to show that the analytical solution can provide a set of valuable design parameters in less time than FEM simulations.