Interpretation of contact geometries from force measurements

As manipulation practice moves toward greater dexterity through the use of more complex end effectors it becomes necessary to sense more details of the interactions between the manipulator and grasped object. Accurate modeling of grasp kinematics is necessary for high quality control of the force and motion states of the grasped object. To do this one must ascertain the location, orientation and type of contact that occurs between fingers and objects. We present an approach for determining geometric features of certain basic types of contact. The characteristics of forces and moments transmitted through point, line and surface contacts are considered and used to determine the number and placement of sensing elements. Several sensor designs are given that use a minimal number of strain gauge measurements to locate the position and orientation of point and line contacts.