Kinematical chain for assisting the motion of a spherical joint

Abstract

A kinematical chain () for assisting a spherical motion of an anatomical joint () of a finger of the hand () of a user, said anatomical joint () having centre of rotation P and being arranged for allowing a relative motion of a finger of the hand () with respect to a portion of hand () of the user, said finger of the hand () defining a longitudinal direction δ. The kinematical chain () comprises a first rotational joint () engaged to the finger of the hand () and to a first connection link (), said first rotational joint () arranged to provide a relative rotation α between the first connection link () and the finger of the hand () about a rotation axis x coincident with the longitudinal direction δ. The kinematical chain () also comprises a third rotational joint () engaged to the portion of hand () and to a second connection link (), said third rotational joint () arranged to provide a relative rotation γ between the second connection link () and the portion of hand () about a rotation axis z integral to the portion of hand (). The kinematical chain () comprises then a second rotational joint () engaged to the first connection link () and to the second connection link (), said second rotational joint () arranged to provide a relative rotation β between the first connection link () and the second connection link () about a rotation axis y. The rotation axes x, y and z intersect in a centre of rotation O, in such a way that the kinematical chain () allows a spherical motion of the longitudinal direction δ with respect to the portion of hand () about the centre of rotation P.