Why does surplus DOF of robot fingers enhance dexterity of object manipulation: analysis and simulation of overall fingers-object dynamics

In order to enhance dexterity in execution of robot tasks, a redundant number of degrees-of-freedom (DOF) is adopted for design of robotic mechanisms like robot arms and multi-fingered robot hands. However, it is said that surplus DOF of such a robotic mechanism incurs a problem of illposedness of inverse kinematics from task space to joint space. This paper attempts to show that, in the case of a pinching task (grasping in 2D space), by using a pair of robot fingers with hemispherical finger ends, 1) the ill-posedness of inverse kinematics can be resolved in a natural and dynamic way by means of sensory feedback signals from task space to joint space and 2) surplus DOF of fingers enhances dexterity of pinching tasks by remarkably accelerating the speed of convergence toward target object manipulation.