Theoretical modelling of soft robotic gripper with bioinspired fibrillar adhesives

Abstract

Soft robotic grippers have gained much attention in recent years owing to their advantages of easy fabrication, flexibility, and adaptability. Inspired by the adhesion capability of gecko’s toe and tree frogs in nature, this study presents a soft robotic gripper made of fiber-reinforced actuator and bioinspired fibrillar adhesives for grasping circular objects with enhanced grasping capability. Theoretical models of the designed gripper are established for characterizing bending angle, blocking force, friction force, and weight-carrying capability. The contribution of this article is the theoretical derivation of an explicit approximation formula for calculating bending angle and grasping force of designed soft gripper under different inflation pressures. Correctness and robustness of the derived formula for bending angle approximation was verified by established three-dimensional finite element model of the designed actuator. With the bioinspired fibrillar adhesives, the friction force between gripper and grasped objects is transformed to load-controlled and area-dependent friction force, which is much greater than that of the traditional design. A two-fingered soft gripper with the newly designed fiber-reinforced actuator is analyzed to verify the derived mathematical model. These models will be beneficial for robotic design/fabrication/control.