Bio-Inspired Self Locking Soft Finger Design with Variable Length for Versatile Stable Grasps

Soft hands have been widely used for grasping tasks due to their high compliance and safety in collaborative tasks. Compared to rigid fingers, they can adapt to wide range of object shapes and sizes and reduce the chance of slippage under uncertainty. However, finger stiffness remains a crucial problem that must be resolved in a definitive way. Several existing methods have been proposed to improve the stiffness of soft fingers, such as jamming, rigid support, mechanical stopper, shape-memory alloys, etc. They often require additional actuators or pumps, large mechanical structures, or high-energy consumables (low reaction time). This paper presents a novel soft finger design which is inspired by the avian feet locking mechanism having high stiffness on both front and side view. This design is flexible; it can adapt to different lengths and shapes of the fingers. The size of the bio-inspired spine is miniature and the reaction time is fast. This paper also presents an interesting inflatable fingertip design which can passively adapt to the displacement of the finger bend and provide robust grasping under dynamic conditions. The proposed soft-finger design has attached to a three-finger gripper base to perform the grasping tests. Results show that the internal spine design can enhance the finger side stiffness 2000% and the front stiffness 70% compare to the normal soft finger design. The grasping stiffness and stability performance is even better than those of rigid fingers in both static and dynamic conditions.