An Ionic-Polymer-Metal-Composite Electrical Model With a Linear Time-Variant Method

Ionic polymer metal composite (IPMC), categorized as an ionic electroactive polymer (EAP), can exhibit conspicuous deflection with low external voltages (∼5 V). This material has been commonly applied in robotic artificial muscles since reported in 1992 because it can be fabricated in various sizes and shapes. Researchers developed numerous IPMC models according to its deflection in response to the corresponding input stimulation. In this paper, an IPMC strip is modeled (1) as a cantilever beam with a loading distribution on the surface, and (2) with system identification tools, such as an autoregressive with exogenous (ARX)/autoregressive moving average with exogenous (ARMAX) model and an output-error (OE) model. Nevertheless, the loading distribution is non-uniform due to the imperfect surface conductivity. Finally, a novel linear time-variant (LTV) modeling method is introduced and applied to an IPMC electrical model on the basis of the internal environment such as surface resistance, thickness, and water distribution related to the unique working principle of IPMC. A comparison between the simulated and the experimental deflections demonstrates the benefits and accuracy of the LTV electrical model.