Accounting for the Interaction Between a Dummy Finger and Joint Modular Soft Actuators for Multi-Joint Support Using a Novel FEM-Based Approach

Soft actuators are safer than rigid robots for hand rehabilitation, yet their performance can be significantly affected by interactions that occur on multi-joint systems. Actuator–finger and actuator–actuator interactions can impact bending output and make actuator performance dependent on the actuation pattern. To address this, we developed and validated a finite element model of a three-joint modular actuator system attached to a dummy finger. The simulation revealed that the displacement between actuators, and the contact area between the fingers and the actuators are key factors influencing actuator performance. We proposed a novel attachment method to enhance contact area and reduce actuator displacement and compared it against five existing designs across two actuator types and three actuation patterns. Our results demonstrate improved bending and reduced dependence of actuator performance on actuation pattern. This study makes a dual contribution to the area of soft robotics for hand rehabilitation by proposing a novel FEM framework for modeling soft actuators attached to multi-joint systems as well as providing insights on attachment method design for soft actuators in hand rehabilitation, emphasizing the importance of actuator-actuator and actuator–finger interactions.