A Biomimetic Soft‐Rigid Hybrid Finger with Autonomous Lateral Stiffness Enhancement

Abstract

The application of soft robotics improves the compliance of robotic fingers, which, however, usually loses sufficient stiffness. Here, a biomimetic soft‐rigid hybrid (BSH) finger that can achieve both inherent compliance and autonomous lateral stiffness enhancement is proposed. Driven by pneumatic artificial muscles, the proposed two‐joined BSH finger can produce two flexion degrees of freedom (DOFs) and one lateral DOF motion. Imitating the human finger anatomy, the BSH finger is designed with elliptical bony ridges and eccentrically arranged ligaments. By leveraging the contact interference of the ridges and tensioning of the ligaments, the lateral stiffness of the BSH finger can be autonomously enhanced through finger flexion. During its natural stage, the lateral stiffness is relatively low to ensure mobility and compliance, while in its flexion stage, its lateral stiffness can increase to resist lateral deflection and high payload. To further investigate the advantages of the design, four BSH fingers are assembled into a robotic hand prototype with three grasping types including enveloping grasp, precise pinch, and power grasp. Experimental results demonstrate that the robotic hand prototype is capable of grasping various objects with a wide range of diameters, lengths, thicknesses, and weights, which will verify the effectiveness of the design methodology.