Development of a 3-fingered hand and grasping unknown objects by groping

This paper addresses the development of a 3-fingered hand and discusses a strategy for grasping unknown objects by groping. First, the design of the developed robot hand is presented. The robot hand has thumb, index finger and middle finger with a total of eight degrees-of-freedom. The location of thumb is designed considering opposability of human hand. Eighty-seven touch sensors are distributed over the surface of palm and fingers of the robot hand. Next, a strategy for grasping unknown objects by groping using the developed hand is discussed. Groping is a kind of "active sensing". When the system does not have any model of object to grasp, active sensing becomes inevitable. The aim of the groping is to find a grasping configuration for unknown objects. A can, ball, cone, plate, and cube are chosen for the unknown objects in the experiments. Experimental results demonstrate the capability of the strategy for grasping unknown objects. This strategy needs neither models of objects nor complicated computation, and therefore, is useful especially for assembly tasks in the real world.