A Biologically Inspired Soft Gripper with the Variable Morphology Palm

Abstract Insufficient grasping force, limited stability, and limited grasping modes have been persistent challenges for soft grippers, garnering increased interest in their studies. This paper presents a variable morphology soft gripper, comprising a variable morphology palm and four finned dual-chamber soft fingers (FDF). Inspired by the fin ray effect, the addition of the fin structure to the substrate of an ordinary dual-chamber soft finger (ODF) enhances the contact area between the finger and the object's surface, thereby increasing grasping force. Based on the structure and motion characteristics of the human hand, a humanoid palm with adjustable morphology is designed to replicate two common human grasping modes: parallel and circular grasping, achieved by transforming the palm's morphology. An end output force model is established, and tests demonstrate its validity, showing the superiority of the FDF in terms of output force. The gripper in circular mode is effective for objects with concentrated mass distribution and regular shapes, gripping objects ranging from 100 g (cookies) to 330 g (pears). The gripper in parallel mode is more suitable for gripping long objects and supports a wider range of object sizes and weights, handling items from 110 g (tissue paper) to 1100 g (box).