Modeling and performance analysis of a trapezoidal section beam for soft robotic fingers using the fin ray effect

Adaptive grasping of diverse objects is crucial for soft robotic fingers. The design of trapezoidal variable-section beams is increasingly recognized for its potential to enhance grasping performance of soft fingers. Despite this widespread interest, a significant gap exists in systematic research investigating how the corresponding structural design enables profound performance effects. The primary challenge hindering such progress pertains to the intricate kinetostatic modeling of fingers, particularly considering variable-section beams. This paper presents a comprehensive closed-form kinetostatic model for a biomimetic fin ray effect (FRE) soft robotic finger based on the modified chained-beam-constraint model. Utilizing a geometry-based contact constraint technique that satisfies the minimum strain energy principle, our model facilitates analysis of stiffness variations and the overall energy dynamics of the finger. We systematically explore the impact of width and thickness variations along the length of longitudinal beams on crucial aspects of grasping performance, including stiffness, energy consumption and adaptability. Our results, which were validated through finite element analysis (FEA) and experiments, demonstrate a tangible improvement in grasp performance over uniform design.