A Novel Fabric-Based Versatile and Stiffness-Tunable Soft Gripper Integrating Soft Pneumatic Fingers and Wrist

This work presents the design and test of a novel fabric-based versatile and stiffness-tunable soft gripper integrating soft pneumatic fingers and wrist. The morphology is designed into a compact tuning fork shape (130 × 110 × 260 mm, 389 g) with two bidirectional sheet-shaped soft fingers and a biaxial bidirectional (universal) cylinder-shaped soft wrist. The multi-degree of freedom of soft fingers and wrist makes the gripper versatile and adaptable to gripping objects of various shapes, sizes, and orientations in a wide range. The bidirectional fingers with double-side inflatable chambers can tune their gripping stiffness and force by varying the common and differential pressure of the two sides. The wrist can tune its deflecting stiffness and force in the same way. Therefore, the gripper can grip objects of various stiffness and weights. The soft gripper is tested to characterize its workspace, stiffness, gripping force, and dynamic response time. Gripping function tests are also performed to evaluate the achieved degree of functions of the gripper. Tests show that the proposed gripper can grip objects in the size of 0-245 mm and in the orientation of -88.2°-90.8° (pitch/roll) with a maximum gripping force of 40 N and a response time of 1.22-1.60 s to force and 0.56-2.61 s to motion, respectively. The gripping stiffness can be tuned in the range of 0.029-0.137 N/mm (i.e., the tunable scope is 79%) by varying common pressure in the range of 0-0.2 MPa. Functional tests verify that the proposed soft gripper is versatile and adaptable to gripping objects of various shapes, sizes, weights, and orientations. Therefore, the proposed soft gripper has great potential applications in production and daily life.