A Human Finger-Inspired Rigid-Soft Hybrid Gripper for Damage-Free and Fast Grasping

Rigid-soft hybrid grippers show good protection and high-payload capacity for fragile and heavy objects. However, because of inadequate actuation speed, it is still challenging for hybrid grippers to grasp moving objects in unstructured environments. To address this limitation, this article presents a rigid-soft hybrid gripper that can manually switch between four grasping modes, enabling it to not only grasp deformable and heavy objects like tofu and a dumbbell, but also capture moving objects with a low response time. Inspired by the structure of human fingers, a rigid-soft hybrid finger with a soft outer body and a rigid inner skeleton is designed. The finger consists of a soft pneumatic actuator (SPA), an endoskeleton linkage, a self-locking mechanism, a fast-responding mechanism, a pneumatic artificial muscle actuator (PAMA), a power transition bolt, and two split pins. The fast response speed of the PAMA and the amplification of the endoskeleton linkage enable the gripper to capture moving objects. A kinematic model is established to verify the endoskeleton linkage's angular velocity amplification ability and describe its bending angle. Experiments demonstrate that the rigid-soft finger can bend to 145.14$^\circ $ within 71 ms. Eventually, the gripper is mounted on a robotic arm to demonstrate that it can grasp fragile and deformable objects, hold heavy objects, and capture moving objects. The grasping strategies and structure of the gripper provide a new idea for designing a high-performance rigid-soft hybrid gripper.