Transition from enveloping to fingertip grasp: a way of reorientation by a multifingered hand

This paper focuses on a specific way of performing reorientation which is often observed when a human hand revolves a cylindrical object by using the whole hand. We put more emphasis on the manipulative task than the firm grip made by enveloping grasp. This paper interprets such reorientation as the sequence of two two-point grasps, one a fingertip grasp, the other an enveloping grasp. We concern ourselves mainly with the two-point grasps and the transition from enveloping to fingertip grasp in the reorientation. This interpretation leads to geometrical conditions that determine whether sliding is necessary for the transition from enveloping to fingertip grasp or not. We present techniques of active sensing to detect or search for the two-point grasps using force sensors attached to the distal links of the fingers