A Linear Time-Variant (LTV) Ionic-Polymer-Metal-Composite (IPMC) Electrical Model With Effects of Capacitors and Resistors

Abstract

For the development and application of various robots, researchers have been looking for adequate materials for external structures and actuators. Ionic polymer metal composite (IPMC), is a type of ionic electroactive polymer (EAP), and this material can exhibit large deflection with low external voltages (∼5 V). This smart material can work in an aquatic environment without the impact from the aquatic pressure, so a swimming robot is one of popular applications of IPMC. Recently, several models in various methods have been found to simulate output deflection. For example, some typical models based on cantilever beams or system identification tools have been used to provide models of IPMC systems. In this paper, however, an electrical model with equivalent passive elements based on existing internal properties is introduced in order to model the system directly. On the other hand, the surface metallic electrodes and the internal Nafion® membrane can be modeled as equivalent resistors according to the properties. Finally, a novel linear time-variant (LTV) modeling method that is different from conventional models is introduced and applied to an IPMC electrical model, built on the basis of the internal environment such as surface resistance, thickness, and water distribution related to the unique working principle of IPMC. Eventually, most of the equivalent elements will change with time in operation, so this electrical model will be revised and describe the entire system more accurately.