Parameter Estimation of the Randles Equivalent Electrical Circuit Using Only Real Part of the Impedance

Abstract

Electrical impedance spectroscopy (EIS) has been widely used in the modeling and analysis of various electrochemical and energy storage systems. Parameter estimation of the equivalent electrical circuit is usually performed with personal computer (PC)-based software platforms that are not commonly available onsite. Such an approach introduces a lag between measurement and maintenance actions. In this article, we present a method for in situ parameter estimation of the Randles circuit ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\textit {RC}}$ </tex-math></inline-formula> equivalent model). Our method overcomes the shortcoming of the iterative and PC-based estimation approaches since there is no need for an initial guess provided by the user. The low complexity of our approach enables the implementation on cost-effective microcontroller-based portable systems. The proposed method has been validated with simulations and with experimentally obtained data. In the simulation part, we used both the noiseless and noisy data, while in the experimental part, we used impedance data obtained from a dummy circuit created with discrete components, as well as bioimpedance of apple slices. The obtained results are compared with desktop-based Multiple Electrochemical Impedance Spectra Parameterization (MEISP) software. Finally, reliable and accurate estimations with a board based on the ATmega2560 microcontroller confirmed the hypothesis of suitability for implementation on embedded hardware.