Dynamic Nonprehensile Manipulation: Controllability, Planning, and Experiments

Abstract

We are interested in using low-degree-of-freedom robots to perform complex tasks by nonprehensile manipulation (manipulation without aformorforce-closure grasp). By notgrasping, the robot can usegravitational, centrifugal, and Coriolisforces as virtual motors to control more degrees of freedom of the part. The part s extra motionfreedoms are exhibited as rolling, slipping, and free flight. This paper describes controllability, motion planning, and implementation ofplanar dynamic nonprehensile manipukltion. We show that almost any planar object is controllable by point contact, and the controlling robot requires only twvo degrees of freedom (a point translating in the plane). We then focus on a one-joint manipulator (with a two-dimensional state space), and show that even this simplest of robots, by using slipping and rolling, can control a planar object to a fulldimensional subset of its six-dimensional statespace. We have developed a one-jointrobotto perform a variety of dynamic tasks, including snatching an object ftom a table, rolling an object on the surface of the arm, and throwing and catching. Nonlinear optimization is used to plan robot trajectories that achieve the desired object motion via coupling forces though the nonprehensile contact.