Increasing the sensitivity of electrical impedance to piezoelectric material parameters with non-uniform electrical excitation

Abstract

To increase the robustness and functionality of piezoceramic ultrasonic sensors, e.g. for flow, material concentration or non-destructive testing, their development is often supported by computer simulations. The results of such finite-element-based simulations are dependent on correct simulation parameters, especially the material data set of the modelled piezoceramic. In recent years several well-known methods for estimation of such parameters have been developed that require knowledge of the sensitivity of a measured behaviour of the material with respect to the parameter set. One such measurable quantity is the electrical impedance of the ceramic. Previous studies for radially symmetric sensors with holohedral electrode setups have shown that the impedance shows little or no sensitivity to certain parameters and simulations reflect this behaviour making parameter estimation difficult. In this paper we have used simulations with special ring-shaped electrode geometry and non-uniform electrical excitation in order to find electrode geometries, with which the computed impedance displays a higher sensitivity to the changes in the parameter set. We find that many such electrode geometries exist in simulations and formulate an optimisation problem to find the local maxima of the sensitivities. Such configurations can be used to conduct experiments and solve the parameter estimation problem more efficiently.