Modeling and modification of fin-ray effect grippers to improve their load capacity and grasp stability

Fin-ray effect (FRE) grippers are very popular because they can passively adapt to different shapes and therefore grasp a variety of objects. To optimize them for different purposes, in-depth analysis of their deformations and internal forces is required, which necessitates accurate mathematical models. This paper presents a modeling framework that improves upon existing approaches by representing all structural components of the FRE finger as Cosserat rods, capturing their continuum behavior. The static forward kinematics problem for these fingers is formulated as the solution to multiple Cosserat rod models with coupled boundary conditions, and the experimental investigations verified the accuracy of the proposed modeling method. Then, simulations were performed to investigate the effects of different design parameters on the grasp forces and conforming to the shape of objects. By defining new boundary conditions, the FRE fingers in simulation could apply more grasp forces and better envelop the objects. Thus, a new mounting adaptor was designed based on the proposed boundary conditions, and the experimental investigations revealed that the modified design could improve the load capacity by up to 150 % and provide more stable grasps for delicate objects in a wide range of shapes and sizes.