Algorithmic Selection of Sliding–Sticking Contacts in Robotic In-hand Manipulation

The paper describes a kinematic method for robotic in-hand manipulation of objects. The method focuses on repositioning the object using a combination of sticking and sliding robotic contacts. Two fingertips with sliding contacts are fixed in space while the remaining two fingertips actively manipulate the object without a change in the point of contact with the object. When sliding over two fixed contacts, the object is constrained to a “three-parameter twist space” if it is not programmed to rotate about the line joining the two fixed contacts. A gradient-descent-based kinematic algorithm is developed to project the desired twist to the allowable twist space, generating a movement sequence of robotic fingertips. The transition from fixed support vis-á-vis the sticking contacts for manipulating the object also emerges from the algorithm.