Design and Characterization of Sectored (Patterned) IPMC Actuators for Propulsion and Maneuvering in Bio-Inspired Underwater Systems

Abstract

The goal of this thesis is to characterize the performance of ionic polymer-metal composite (IPMCs) propulsors for underwater applications, namely for propelling and maneuvering small bio-inspired autonomous systems. Specifically, this work examines the capabilities of IPMCs with sectored (patterned) electrodes. The electrode pattern on the surface of the ion exchange membrane is created, for example, using a straightforward surface-machining process. These IPMCs have recently been fabricated for realizing bending and twisting motion, where the main application is for creating next-generation artificial fish-like propulsors that can mimic the undulatory, flapping, and complex motions of real fish fins. Not only can the sectored IPMCs be used for actuation, but sections of the composite material can be employed as a sensor, for sensing fin deformation and responses to external stimulation. The result is a compact monolithic control surface with integrated sensing for multifunctional applications. Herein, a thorough experimental study is performed on IPMCs with sectored electrodes to characterize their performance. In particular, results are presented to show (1) the achievable twisting response; (2) blocking force and torque; (3) propulsion characteristics; (4) power consumption and effectiveness. These results can be utilized to guide the design of practical marine systems driven by IPMC propulsors. For example, a bio-inspired robotic system capable of ostraciiform locomotion with the potential to control pitch, roll, and yaw through complex twisting of the pectoral and tail fins is developed. The maximum speed for the initial prototype is measured at 2.8~cm/s. It is noted that significant improvements in swimming speed can be made, for example, by optimizing the IPMC-caudal fin geometry.