Development of a soft finger-joint mechanism for human-care robot

In this paper, we propose a joint mechanism that enables a robot to generate multi-directional passive compliant motions and to estimate the external torque. In this joint, silicone gum cushions are used as elastic elements to transmit motion from an actuator to an output link. The cushions are positioned between the link and the motor-driven disks. The elastic deformation of the cushion contributes to both the generation of passive compliant motion for external torque and the estimation of the external torque. We applied the proposed mechanism to the metacarpal-phalangeal joint (MP joint) of the finger of a robot designed for human-care services. In addition, the basic characteristics of the mechanism are demonstrated in several experiments.