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

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.