Compliant underactuated grasper

A compliant underactuated grasper comprising:

• a palm base;
• first and second fingers, wherein each of the first and second fingers comprises:
• a proximal phalanx;
• a distal phalanx;
• and
• a compliant flexure joint connecting the distal phalanx to the proximal phalanx;
• and
• first and second rotation joints connecting the first and second fingers, respectively, to the palm base to enable rotation of the first and second fingers relative to the palm base, wherein the first and second fingers can be rotated relative to the palm base about the first and second rotation joints to reorient the first and second fingers with respect to the palm base and to change an angle defined between a pivot axis of the first finger and a pivot axis of the second finger;
• wherein the distal phalanx of each of the first and second fingers includes:
• a rounded end face;
• and
• a lifting portion including a lifting edge adjacent the rounded end face;
• wherein each of the first and second fingers further includes a tendon cable for moving the proximal and distal phalanges such that movement of the tendon cable generates angular motion of the proximal phalanx about the pivot axis of the finger at a greater rate than angular motion of the distal phalanx about the flexure joint;
• and
• wherein, with respect to each of the first and second fingers:
• the proximal phalanx is connected to the palm base for rotation about the pivot axis in a first direction and a second direction;
• the grasper includes a return biasing spring to drive the proximal phalanx in the second direction to a return position;
• the return biasing spring has a first spring rate;
• the flexure joint is configured to bias the distal phalanx into an open position relative to the proximal phalanx and has a second spring rate;
• and
• the second spring rate is greater than the first spring rate.