“Equivalent” Electromechanical Coefficient for IPMC Actuator Design Based on Equivalent Bimorph Beam Theory

Abstract

This paper addresses an "equivalent" electromechanical coupling coefficient that may be used in designing Ionic Polymer Metal Composite (IPMC) actuators. The coefficient is not a material constant and derived from equivalent bimorph beam model. The collective effect of the membrane thickness and operating voltage on the coefficient is demonstrated by using a design of experiment (DOE) of three and five levels of the two factors, respectively. Experiments and linear finite element analyses with MD.NASTRAN at DOE points are performed. The tip displacement and the coupling coefficient are reported and their response surface (RS) approximations as function of the thickness and voltage are constructed. Experiments and RS predictions indicate that actuator thickness and applied voltage are two interacting major factors for maximum tip displacement. The equivalent coupling coefficient is primarily driven by the thickness of actuator moreover voltage appears to contribute as the thickness increases. The initial curvature of the strips before electrical excitation is also shown to be a factor for "equivalent" coupling coefficient, it is not, however sufficient to explain the variation in the experimental data. A correction factor approach is proposed and applied to the straight beam tip displacement RS that filters out experimental variation. A corrected RS enables including the pre-imposed initial curvature as design parameter along with the actuator thickness and the operating peak voltage when predicting the tip displacement and the equivalent coupling coefficient.

A Non-Linear Dynamic Model of Ionic Polymer-Metal Composite (IPMC) Cantilever Actuator

“…Further, increase in frequency drives to the critical point C, beyond which the system again exhibits stable condition. It is further observed that, frequency beyond point C, the amplitude decreases to point D. This observation is consistent with the results presented by [5,31]. If the system is driven by a voltage with frequency in between point X and C the response will be thus unstable and may results in failure in this range.…”

Accurate Dynamic Modeling of Helical Ionic Polymer-Metal Composite Actuator Based on Intrinsic Equations

“…Because of the helical structure of the IPMC actuator, the helical bimorph beam model is newly developed for obtaining the electromechanical coupling coefficient, which can be considered as equivalent material parameter for the finiteelement analyses [47], [48]. The geometry of the proposed helical IPMC actuator is simply modeled by using the 3-D modeling software package.…”

A review on IPMC material as actuators and sensors: Fabrications, characteristics and applications

“…Cilingir et al 37 used design of experiments (DOE) to demonstrate the effect of thickness and operating voltage on the coefficient which are also main factors for maximum tip displacement. They also stated that the curvature of the IPMC strip before excitation is one of the factors for "equivalent" coupling coefficient.…”

“…The advantage of their approach is that although the IPMC actuation is a transport phenomenon, it is treated as response by piezoelectric materials which are easier to model in commercial finite element analysis software. 37 …”