Modeling and Control for Object Manipulation by a Two d.o.f. Robotic Hand with Soft Fingertips

In this paper we present a general dynamic model that describes the two-dimensional grasp by robotic fingers with soft rolling fingertips. The fundamental aspect of our analysis is the derivation of the system's kinematics and dynamics by incorporating rolling constraints that depend on the deformation and on the rolling distance characteristics of the fingertips’ soft material. Using this model, a controller is proposed, which can regulate the orientation of the object at a desired angle, whilst maintaining a stable grasp with a desired internal normal force. We evaluate the dynamic model under the proposed control law by simulations and experiments that make use of two different types of soft fingertip material (silicone and foam), to highlight the effect of deformation and rolling distance characteristics.