Accession Number : ADA186419

Title :   The Synthesis of Stable Force-Closure Grasps.

Descriptive Note : Master's thesis,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE ARTIFICIAL INTELLIGENCE LAB

Personal Author(s) : Nguyen, Van-Duc

PDF Url : ADA186419

Report Date : Jul 1986

Pagination or Media Count : 136

Abstract : The thesis addresses the problem of synthesizing grasps that are force-closure and stable. The synthesis of force closure grasps constructs independent regions of contact for the fingertips, such that the motion of the grasped object is totally constrained. The synthesis of stable grasps constructs virtual springs at the contacts, such that the grasped object is stable, and has a desired stiffness matrix about its stable equilibrium. A grasp of an object is force-closure if and only if we can exert, through the set of contacts, arbitrary forces and moments on the object. So force-closure implies equilibrium exists because of zero force and moment is spanned. In the reverse direction, a non-marginal equilibrium grasp is also a force-closure grasp, if it has at least two point contacts with friction in 2D, or two soft-finger contacts of three hard-finger contacts in 3D. All force-closure grasps can be made stable, by using either active or passive springs at the contacts. A simple relation is developed between the stability and stiffness of the grasp and the spatial configuration of the virtual springs at the contacts. The stiffness of the grasp depends also on whether the points of contact stick, or slide without friction or straight or curved surfaces of the object.

Descriptors :   *CLOSURES, *ROBOTS, CURVATURE, EQUILIBRIUM(GENERAL), FRICTION, MATRICES(MATHEMATICS), MOMENTS, PASSIVE SYSTEMS, REVERSIBLE, SPATIAL DISTRIBUTION, SPRINGS, STABILITY, STIFFNESS, SURFACES, SYNTHESIS, THESES, CONTROL SYSTEMS, THESES

Subject Categories : Biomedical Instrumentation and Bioengineering
      Couplers, Fasteners, and Joints

Distribution Statement : APPROVED FOR PUBLIC RELEASE