Friction, Stability and the Design of Robotic Fingers

For practical reasons, compliant materials are often used on the gripping surfaces of robotic hands. Such materials are not well described by the Coulomb friction law or by simple point-contact or line-contact kinematics. In this paper, a shearing model is used to describe the contact friction. Models ofpointed, curved, flat, soft, and soft-curved fingertips are then developed and compared in terms of their contribu tion to the stiffness and stability of a simple grasp. There is a spectrum of contact conditions defined by the fingertip radius and contact area relative to the object size. This spectrum provides insights for designing and controlling robotic fingers.