Use of Grasp Force Focus Positioning to Enhance the Torque Resistance Capability of Robotic Grasps.

摘要

Three-point-contact grasps are unique in that the homogeneous solution for the contact forces always produces a grasp force focus. Careful positioning of this focus point in the grasp plane can help avoid two things; slipping at the contact points, and violation of joint torque limits. The focus placement method is explored theoretically by examining two types of grasps on cylinders; 1) fingertip grasps using three independently operated fingers, and 2) single-finger power grasps with one contact point on each of three links. Constraint maps are generated for various fingertip grasps in order to show how proper placement of the grasp force focus results in no-slip grasps. A specific single-power grasp, using a specific manipulator, is examined in order to show that joint torque limits also effect focus placement. The results show that optimal focus location is grasp-specific, and that torque direction also plays a role in the torque resistance capability of the grasp.