The Characteristics of Human Prehension Based on the Form of the Palm of a Hand and Finger Contact Condition

Abstract

The human hand can perform various types of prehension, that is, grasp, grip, pinch, and nip an object. In order to enable a robot hand to do various types of prehension, it is necessary to make clear the function of the palm of a hand and the contact condition (grasping force, contact area, and its centroid) of each finger. From experimental analysis, the form of a palm of a hand is determined mainly from the shape of the object and the type of prehension, and varies with the thickness or diameter of the object. There is a logarithmic linear relation between the grasping force and the contact area in each finger. The grasping force becomes about 1.7 times as large as the weight of the object. If the thickness of the object is large, the medical and the fifth fingers p]ay an important role in various types of prehension.