Expanded Workspaces of Manipulation Devices Using Friction and Dynamics

Dynamic or “nonprehensile” grasps that do not rely on a dedicated fixturing device, but instead use dynamic forces to maintain control of an object, reduce the necessary hardware complexity over traditional, “pick-and-place” robotic manipulation strategies. The full workspace of such a manipulator, however, is dependent on the history of the mechanism’s motions and can no longer be determined simply by the geometric constraints imposed by the physical dimensions and limits of the mechanism. As others have previously, we solve the dynamic equations with the imposed kinematic and force constraints, then visualize the extent of motion by observing the limiting trajectories on a phase plane. As opposed to incorporating all constraints initially, however, we examine constraints independent of others before combining. This unobscures how each constraint individually affects the total system ability and gives additional insight during the design phase of a mechanism, where a judicious choice of system parameters is needed. We then describe the utility of this constraint separation by analyzing a simple mechanism useful for lifting operations.