Feasibility study of pinching of a rigid object with non-parallel flat surfaces

This paper is aiming at clarifying the relationship between the total DOF (degree-of-freedom) of a pair of robot fingers and feasibility of concurrent control of stable grasping and object manipulation of a rigid object with non-parallel surfaces under the gravity effect. It is shown by computer simulation and an actual experiment that if each finger has at least two DOF then the desired task of concurrent stable grasping and posture control can be attained, though the use of a pair of dual fingers with three DOF is shown theoretically to be feasible. It is also shown that the use of fingers with single DOF and two DOF cannot be feasible under the gravity effect, though it is feasible in the case that the gravity effect can be ignored.