A novel coupled gesture-changeable under-actuated robotic finger with linkage and gear-rack mechanism

Abstract

Design of a novel under-actuated finger was proposed in this paper. The coupled gesture-changeable finger overcomes disadvantages of two convenient kinds of under-actuated finger: coupled finger and self-adaptive finger. Decided by different grasping targets, the finger's operation process is divided into three kinds: coupled only process, self-adaptive only process and coupled self-adaptive process. The first process takes place when distal phalanx touches object's surface earlier than the proximal one. When external force pushes the object, self-adaptive process works. In other circumstances, grasping process belongs to the last kind and falls into two stages: coupled stage and self-adaptive stage. In the beginning, rate of proximal phalanx's rotation angle to distal phalanx's angle is mathematically predictable, which is decided by the geometrical relationship among mechanical structures. Then, the upper slider touches the object's surface and self-adaptive stage begins. The sliders separate by the object's push, thus decoupling. Decoupling is driven by external force rather than actuator energy. With linkage and gear-rack mechanism, the new finger saves energy and performs more efficiently dealing with various kinds of object. Simulation and optimization were also done in the paper.