Mechanical Analysis of Grasps with Defective Contacts Using Polyhedral Convex Set Theory.

Abstract

Contacts with insufficient degrees of freedom are defined as defective contacts. Although defective contacts are found in the power-grasp and the enveloping grasp of a multifingered robot hand, the mechanical characteristics are not yet studied in depth. In this paper, an approach to the mechanical analysis of grasps with defective contacts is presented. The relations among joint torque space, contact force space, friction cone, admissible external force space are made clear. By using the convex analysis, we represent these sets in the external or internal representation of polyhedral convex set. Finally, the validity of our approach is illustrated by a numerical example.