No abstract

We propose a planning method for a gripper grasping daily life objects using quadric surface approximation. This method can decompose the objects to the approximate quadric surfaces. The planner can find regions for contacting fingers quickly so that the gripper grasps the object firmly. The planner evaluates the grasp stability for these postures. The previous evaluation method in surface contact considers contact area only. We extend the evaluation method for considering stress distribution. We performed simulation and verified the effectiveness of our grasp planning.

This paper presents a grasp planner which allows a robot to grasp the constricted parts of objects in our daily life. Even though constricted parts can be grasped more firmly than convex parts, previous planners have not sufficiently focused on grasping this part. We develop techniques for quadric surface approximation, grasp posture generation, and stability evaluation for grasping constricted parts. By modeling an object into multiple quadric surfaces, the planner generates a grasping posture by selecting one-sheet hyperbolic surfaces or two adjacent ellipsoids as constricted parts. When a grasping posture being generated, the grasp stability is evaluated based on the distribution of the stress applied to an object by the fingers. We perform several simulations and experiments to verify the effectiveness of our proposed method.

This paper discusses the grasp stability under gravity where each finger makes soft-finger contact with an object. By using the intersection of polygon models between a finger and an object, the contact area between a finger and an object is obtained. Then, by assuming the Winkler elastic foundation model, the pressure distribution within the contact area is obtained. By using this pressure distribution, we determine the grasp stability under soft-finger contact. We further consider defining a quality measure of the soft-finger grasp by assuming that, while the gravitational force is applied to an object, the direction of gravity is unknown. To demonstrate the effectiveness of the proposed approach, we show several numerical examples. Finally, we show an experimental results on identification of physical parameters of elastic material attached at the finger surface.