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.