Robot Finger Module With Multidirectional Adjustable Joint Stiffness

This paper describes a novel finger mechanism that enables a robot to perform a gentle and dexterous motion. This finger contains three joints, in which the proximal (PIP) and distal intraphalangeal (DIP) joints are coupled rigidly, and the metacarpophalangeal (MP) joint has a multidirectional passive compliance that is adjustable as in humans. In the MP joint, two kinds of silicone-rubber cushions (A-SRC and B-SRC) are placed between a motor-driven disk and an output link. A-SRC plays three roles: 1) transmission of the rotational motion from the motor to the output link by the friction force between the surface of A-SRC and the motor-driven disk; 2) absorption of external forces from multiple directions by its elastic deformation; and 3) sensing the directions and magnitudes of external forces with the change in inside pressure. B-SRC adjusts the characteristics of joint compliance by pressing A-SRC against the motor-driven disk. We investigate the basic performance of this finger module through several experiments.