Analysis of Fingertip Motion for Precise Object-Handling

This paper analyzes the static motion of multijointed fingers and proposes a control procedure for the fingers to locate an object at a desired position and in a desired orientation precisely. In the analysis, each finger is assumed to have a ball-like form. Cooperative motions of two fingers which generate simultaneous finger operation are considered only in the situation that the relative positions of the grasping fingers and the grasped object are kept the same as those in the initial state. Cooperative motions are classified into the next three types according to the fingers used. 1) two fingers of Fm and Fm, 2) two fingers of Fm and Ff, 3) one finger of Fm, where Fm means the finger which has an ability to control both the position of its fingertip and the orientation of its most distal link, and Ff means the finger which has an ability to control only its position. A sequential control of 2) and 3) realizes an equivalent result of 1). Experimental results of tilting a board have shown that the control procedure obtained from the analysis makes an autonomous precise handling of an object easy.