FE‐based modeling of a mesoscale piezoelectric motor

Abstract

AbstractThe manufacturing of systems at the mesoscale on the order of millimeters to centimeters is costly and challenging. To simplify the development process, the finite element method (FEM) can be used to compare and evaluate different design variations at an early stage. This method also allows for gaining a more precise understanding of the system's behavior. In robotic applications it is the torque that is of the greatest interest as a sufficiently high torque mitigates the need for a gearbox, which is very difficult to manufacture and integrate at small scales. Given this background, the present work aims to develop a finite element model for the numerical representation of a class of rotational piezoelectric motors based on multiple unimorph arms. The influence of different design parameters on the resulting torque is analyzed utilizing this model. The motor design consists of a planar rotor and a flat spring, a stator with three unimorph arms, as well as a shaft. With a total integrated motor thickness of 0.8 mm, the weight is approximately 200 milligrams. The rotation is mainly caused by the tip contact between the arms of the stator and the rotor itself. Experiments with prototypes have shown that bidirectional rotation is possible with the design, which is then investigated in more detail using the numerical model. There are several challenges here in the non‐linearity due to the contact between the individual components and the high‐frequency excitation of the motor in the kHz range.The modeling also requires validation experiments to determine the resulting properties for the coupled system of structural and piezoelectric components. This includes both the measurement of the unimorph arms and the measurement of the natural frequencies of the stator with the piezoelectric unimorphs by a laser scanning vibrometer and displacement sensors. The scanning vibrometer also provides the opportunity to compare the vibration modes, as an important non‐local output quantity, in order to achieve good agreement between the numerical and experimental results.In the next stage, the model is to serve as the basis for multi‐objective optimization to achieve maximum torque in the smallest possible volume. Further miniaturization possibilities will also be investigated in future studies.