Modeling and inverse compensation of dynamics of base-excited ionic polymer–metal composite sensors

Abstract

Motivated by their structural monitoring and energy harvesting applications, in this article, we study the modeling and inverse compensation of cantilevered ionic polymer–metal composite sensors that are excited at base. The proposed dynamic model is physics based, combines the vibration dynamics of a flexible beam under base excitation and the ion transport dynamics within an ionic polymer–metal composite, and incorporates the effect of a tip mass. Excellent agreement is demonstrated between the model prediction and experimental measurement in both the magnitude and the phase of the frequency response, for the frequency range of 10–150 Hz. For the purpose of real-time signal processing, we further reduce the model to finite dimension by combining techniques of Padé approximation and Taylor series expansion. For the reconstruction of the base excitation signal given the sensor output, we present an inverse compensation scheme for the reduced sensor model, where stable but noncausal inversion and leaky integration are introduced to deal with zeros that are unstable and on the imaginary axis, respectively. The effectiveness of the scheme as well as the underlying model is validated experimentally in the reconstruction of structural vibration signals, when the structure to which the ionic polymer–metal composite is attached is subjected both to periodic vibrations and to an impact.