OS hand: Octopus-inspired self-adaptive underactuated hand with fluid-driven tentacles and force-changeable artificial muscles

Inspired from flexible bending of octopus' tentacles and outside-driving kind of traditional hand exoskeletons, this paper proposes a novel self-adaptive underactuated multi-fingered hand (OS Hand), which has four flexible tentacles. Each tentacle is similar to an octopus' tentacle, and consists of an artificial muscle which goes through all joints, eight serial-hinged joints, and force-changeable assembly. The force-changeable assembly is mainly composed of a spring and elastic rubber membrane, which is coordinated for stable grasping by a layer of rubber material in the surface of the tentacle. Each tentacle can execute different grasping modes depending on the shapes and dimensions of the objects grasped and grip objects in a gentle and form-fitting manner. The OS Hand combines good qualities of both powerful grasp of traditional grippers and form-fitting grasp of flexible hands. Kinematic analysis and mathematic model disclose the distribution of contact forces and compare the tentacles in the OS Hand with traditional rigid tentacles. Experimental results show that the OS Hand is valid for precise pinching, self-adaptive powerful encompassing, and grasping forces are freely changeable in a wide range. With the advantages of high self-adaptation, various grasp configurations and large range of grasping forces, the OS Hand has a wide range of applications in the area of service robotics which requires a lot of flexible operations of general grasping, moving, and releasing.