An Exploration of Nonprehensile Two-Palm Manipulation

This paper describes our current research into nonprehensile palm manipulation. The term “palm” refers to the use of the entire device surface during manipulation, as opposed to use of the fingertips alone. The term “nonprehensile” means that the palms hold the object without wrapping themselves around it, as distinguished from a force/form closure grasp often employed by a fingered hand. Indeed, nonprehensile operations such as purposeful sliding and constrained dropping constitute important palm primitives. We have implemented a system for orienting parts using two palms. The system consists of a planner and an executive. As input, the system expects a geometric description of a part, its center of mass, the coefficients of friction between the part and each of the palms, and a start and goal configuration of the part in stable contact with one of the palms. As output, the system computes and executes a sequence of palm motions designed to reorient the part from the specified start to the specified goal configuration.