Shape estimation of IPMC actuators in ionic solutions using hyper redundant kinematic modeling

•Hyper redundancy resolution of Ionic Polymer Metal Composites (IPMC)•Elimination of 3 dimensional perspective error while actuator tip tracking•Shape variation of differentially doped IPMC actuators in various ionic solutions•Shape correspondence between the actuated IPMC trace and the natural Tractrix curve

Ionic Polymer Metal Composites (IPMCs) has established itself as an ionomer rendering wide-ranging applications spanning the paradigm of robotics to medical appliances, thereby drawing significant research interests. Prior studies to characterize IPMCs have been conducted over several years but efforts on its kinematic modeling have remained inchoate. The bending profile of IPMC changes when placed in different ionic solutions. The IPMC trace along with its tip location characterizes its complete behavior upon low level actuation. This article aims at identifying the bending patterns of an IPMC actuator, decomposing it as a 20-link hyper-redundant serial manipulator. The Tractrix based inverse kinematics engine is used to study the polymer profile in distilled water, 1.5 N LiCl and NaCl solutions respectively. The proposed algorithm yields a natural curve (Tractrix) which resembles the profile traced by an actuated IPMC strip — enabling its use in potential applications which would require a foresight of the actuator workspace.