Dynamic Grasping for Object Picking Using Passive Zero-DOF End-Effectors

This letter presents a new grasping approach that utilizes object inertia for picking objects using end-effectors that have no actuated degrees of freedom. The end-effector provides two contacts at a fixed distance, not necessarily antipodal, on two opposing edges of a convex object. The object is dynamically swept off of a position at rest to a goal position at stable rest while maintaining stability throughout the motion by assuring accelerations and torques from the path provide stabilizing forces in the passive gripper. Since the end-effector lacks the ability to close on the object, and the same is only subjected to the force of gravity and the applied external acceleration and torque, no internal forces are applied to the object. Practical applications for this method include very low complexity, affordable end-effectors for pick-and-place applications, and also sensorless transferring of objects in human-robot interaction. Implementation and experimentation using a conventional manipulator with three passive gripper geometries with 11 different common household objects demonstrate usefulness of the proposed method.