Enhancement of dexterity in robotic grasping referring to characteristics of human grasping

This paper is concerned with a problem of enhancement of dexterity in pinching a rectangular object and controlling its orientation by a pair of robot fingers with multi-DOFs similar to the thumb and index finger of human. When human grasps an object, two motions of pinching and orientating the object are simultaneously addressed smoothly and agilely. However, in the case of robotic fingers, it is beyond the capacity of them to execute the two tasks concurrently, and even if the tasks are executed, much time is required to finish. In order to enable robotic fingers to carry out the tasks concurrently and dexterously, this paper proposes two methods obtained from referring to functional and morphological characteristics of human fingers, which are 1) rolesharing joint control and 2) modification of finger-tip radius. In order to evaluate the effectiveness of the proposed methods, computer simulations of concurrent pinching and orientation control are conducted and the obtained results are analyzed from the viewpoint of enhancement of dexterity by using a proposed concept of dexterity index. Finally, it is verified that the proposed methods reduce the time of execution remarkably in concurrent pinching and orientation control.