Characterization of the precision manipulation capabilities of robot hands via the continuous group of displacements

Abstract

Abstract-In robot hands, precision manipulation, defined as repositioning of a grasped object within the hand workspace without breaking or changing contact, is a fundamental operation for the accomplishment of highly dexterous manipulation tasks. This paper presents a method to characterize the precision manipulation capabilities of a given robot hand regardless of the particularities of the grasped object. The technique allows determining the composition of the displacement manifold (finite motion) of the grasped object relative to the palm of the robot hand and defining the displacements that can actually be controlled by the hand actuators without depending on external factors to the hand. The approach is based on a reduction of the graph of kinematic constraints related to the hand-object system through proper manipulations of the continuous subgroups of displacements generated by the hand joints and contacts. The proposed method is demonstrated through three detailed and constructive examples of common architectures of simplified multi-fingered hands.

Gross Motion Analysis of Fingertip-Based Within-Hand Manipulation

“…Hence, there are not uncontrollable degrees of freedom in the hand-object system (step 5). This example was also discussed in [13] with equivalent results, but here we amend some of the steps in the deduction of equation (13).…”

“…A comprehensive list of nonidentity intersections between subgroups of displacements can be found in [11] (Table C.3). A preliminary version of the presented framework for manipulation characterization was introduced in [13], where it was limited to contacts modeled as point contact with friction. In this work, we further extend that framework by modeling the effects of a fingertip contacting a body as kinematic chains using an extension of the Bruyninckx-Hunt approach of surface-surface contact [14], what allows using all standard contact categories of robotic manipulation (e.g., point contact with friction, soft finger) as well as other contact models, such as ball, tubular, and frictional adaptive finger contacts.…”