Kinematic design of an ejection-free underactuated anthropomorphic finger

This paper presents preliminary results on the design of a novel architecture of a three-phalanx underactuated finger. An ejection-free underactuated anthropomorphic hand is of the greatest interest for the field of humanoid robots. So far, all underactuated fingers lead to ejection for certain configurations. By using a second system of actuation in a three-phalanx finger, the zone of instability of this finger is reduced and the ejection problem is prevented. Hence, the mathematical model of this finger is first introduced, followed by the choice of transmission ratios to be taken for the two pulley systems. Finally, the zone of instability of this new architecture is presented where it is proved that ejection is avoided.