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

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

Development of two jaw compliant gripper based on hyper-redundant approximation of IPMC actuators

Ionic Polymer Metal Composites (IPMC) have emerged as an actuator for gripping soft as well as rigid objects, owing to their compliance and good scalability. Their use in precision gripping necessitates the absence of any ambivalence in its characterization to ensure grasp stability. This article proposes an alternative approach to model IPMCs, contrary to prior attempts that have employed cantilever deflection theories. The bending patterns of the actuator soaked in distilled water and LiCl solution are studied using a Tractrix based hyper-redundant kinematic algorithm. Two distinct gripper designs comprising of a conventional two jaw as well as a modified passive jaw gripper have been investigated to ascertain their traversed workspaces in the aforementioned mediums. A prior knowledge of this working-area ensures an effective design of target-specific gripper configurations adept to negotiate objects with varied surface profiles. The results obtained after experiments indicate that IPMCs infused in LiCl solution exhibit a characteristic curvilinearity, suited for ensuring surface contact with the object. However the ones hydrated in de-ionized water demonstrate linear bending, apt for generating point contact. Though the passive-jaw gripper showcases a smaller workspace with respect to the active ones, yet it conveys a vital information regarding the contact force exerted on an object surface by the polymer jaw