Novel mechanism of artificial finger using double planetary gear system

This paper presents a new mechanism for artificial fingers. It enables adduction/abduction of the MP joint in addition to the synergetic flexion/extension of the DIP, PIP and MP joints. The key mechanism is the newly invented double planetary gear system (DPGS) that allows three DOF motions of the finger in a compact placement of all actuators in a palm. The DPGS receives three input torques; two are active torques coming from DC-motors, which drives solar gears, the other one is a passive torque loaded at the carrier of the planetary gears generated by a spring. This active / passive hybrid actuation enables to grip unknown shape objects with no sensory feedback. This paper describes the kinematics and the kinetics of the newly developed mechanism followed by the kinetics of pinching the object by two-fingers. It also shows the results of a couple of experiments. Additionally, we show a new mechanical design aiming for constructing a multi-fingered hand.