An effective modelling approach to estimate nonlinear bending behaviour of cantilever type conducting polymer actuators

This paper reports on the establishment of an effective yet comprehensive modelling approach that enables (i) to determine the large and nonlinear bending displacements (i.e., deflections) of conducting polymer actuators, widely known as artificial muscles, and (ii) estimate the actuator parameters such as the effective modulus of elasticity. These actuators are fundamentally one-end fixed and the other end free cantilever structures, undergoing large deflections under an electrical potential difference. The classical beam theory fails to predict their bending behaviour such as the tip deflections accurately. Based on the operation principle of the electroactive polymer actuators and the large deflection Euler-Bernoulli equation, the bending displacement models are formulated for a cantilever beam under a continuously distributed load. These nonlinear models have been used to estimate the moduli of elasticity of the actuators, utilizing a nonlinear least square estimation algorithm, and experimentally measured longitudinal and transverse tip deflections. Parametric models relating the voltage input to the cylindrical coordinates of the tip deflection are also identified and experimentally validated. These models were further validated for a new set of experimental data such that the modelling approach is effective enough to estimate nonlinear deflection of the actuators and estimate actuator parameters such as the moduli of elasticity of the materials constituting polymer actuators. The modelling approach can be extended to mimic the bending behaviour of other ionic-type conducting polymer actuators. (C) 2009 Elsevier B.V. All rights reserved.