Robotic finger with coupled joints: A prototype and its inverse kinematics

Without an external load or without a special effort to overcome the coupling, human fingers move in such a way that DIP and PIP joints of each finger except of a thumb move simultaneously in a coupled fashion. Similar motion of robotic fingers can be achieved by independent control of each joint, but to reduce number of needed actuators, a mechanical coupling of respective joints is frequently used. In this paper we derive an algebraic solution of inverse kinematics for robotic finger with linearly coupled PIP and DIP joints. The calculation involves solving a polynomial. A prototype of robotic finger with coupled joints that uses newly proposed mechanism called "Twist Drive" is presented. The principle of proposed joints actuation mechanism and its main characteristics are explained. A prototype of robotic finger and basic experimental results of joint positioning control are presented.