Torsional Stiffness Improvement of a Soft Pneumatic Finger Using Embedded Skeleton

Silicone-based pneumatic actuators are among the most widely used soft actuators in adaptable fingers. However, due to the soft nature of silicone, the performance of these fingers is highly affected by the low torsional stiffness, which may cause failure in grasping and manipulation. To address this problem, a compact design is proposed by embedding a rigid skeleton into a soft pneumatic finger. A finite element approach with an analysical model is used to evaluate the performance of the fingers both with and without the skeleton. Then, a series of experiments is performed to study the bending motion and rigidity of the fingers. The results reveal that the skeleton increases the torsional stiffness of the finger up to 300%. Furthermore, the consistency with the experimental data indicates the good precision of the proposed modeling method. Finally, a two-finger hand is designed to evaluate the performance of the reinforced finger in reality. The grasp experiments illustrate that the hybrid finger with the skeleton is highly adaptable and can successfully grasp and manipulate heavy objects. Thus, a potential approach is proposed to improve the torsional stiffness of silicone-based pneumatic fingers while maintaining adaptability.