Abstract:  In response to the issue of previous research primarily focusing on optimizing existing finger structures, but lacking in structural design based on the desired grasping performance, an optimization design method for a variable stiffness soft finger based on a grasping force compensation strategy was proposed. Firstly, to comprehensively assess the grasping performance of the soft finger, three evaluation metrics were introduced. To achieve earlier and more linear changes in grasping force and enhance grasping stability, a design strategy utilizing the characteristics of variable stiffness mechanism to compensate for the grasping force was proposed, resulting in the development of a cantilever beam variable stiffness finger. Then, the ANSYS finite element analysis software was employed, along with a multi-objective optimization approach, to optimize the cantilever beam variable stiffness finger's structure. The variable stiffness properties of the cantilever beam finger were analyzed and compared with the grasping performance of the basic finger structure. Finally, a testing platform was constructed to conduct grasping performance experiments and validate the simulation results. The research outcomes indicate that comparing to the basic finger structure, the finger obtained through the grasping force compensation strategy shows a 33.3% advancement in the grasping force response point, with a linear fitting coefficient (R2) of 0.9997 for the grasping force variation in the later stage, and a reduction of approximately 71.4% in the grasping force direction angle. The experimental results of grasping force align closely with the simulation, with a maximum error of less than 0.5 N for the grasping force magnitude and less than 4° for the grasping force direction angle. These results demonstrate that the grasping force compensation strategy can guide the design of soft fingers and effectively enhance their grasping performance.
Key words:  grasp performance of soft finger; grasping force response; compensation strategy; adaptive; cantilever beam structure variable stiffness finger; ANSYS finite element analysis