Dexterous manipulation with underactuated elastic hands

In this paper we show that it is possible to design underactuated robot hands capable of performing dexterous manipulation tasks, despite the fact that the motion of an underactuated hand is not fully constrained by its actuators. If a robot has elastic elements at its joints, then the velocity of the actuators can be mapped onto the velocity of the grasped object using elastic averaging. This mapping can be used to compute classical measures of manipulability for an underactuated hand. We also demonstrate that holonomically constrained grasps can be analyzed to determine the manifold of stable object configurations that can be reached from some initial grasp. This is especially useful for planar manipulation operations, such as twisting a knob or precision positioning. A prototype two-fingered planar underactuated hand is introduced, having the ability to stably grasp and manipulate objects within the hand.