Enhancing Embedded Impedance Spectroscopy through Optimized Multisine Signal Design: Application to Li-ion batteries

Excitation signals play a key role in impedance spectroscopy and have to be optimized in terms of signal shape, amplitude, and signal duration. Excitation signals with a very low amplitude lead to a noisy measurement result, while signals with a high amplitude can lead to considerable stability problems for the test specimen. Multifrequency excitation signals shorten the measurement time considerably but require optimization in order to achieve sufficient excitation at all addressed frequencies without exceeding the limits specified by the linearity condition of impedance spectroscopy. After optimization, multisine excitation signals can even achieve better performance than sine signals by shortening the signal duration and maintaining the stability of the DUT. In this paper, we propose a design methodology for multisine signals that provides optimization of frequency ranges to reduce spectral losses, optimized phase distribution to improve the crest factor of the resulting signal, and reduced measurement time. We also propose a phase optimization based on the Evolutionary Role-Playing Game Theory (ERPGT) to ensure the stability of the DUT during the measurement time. With this method, significantly lower load fluctuations, a higher signal-to-noise ratio, and a lower total harmonic distortion can be achieved.