Adjustments to Local Friction in Multifinger Prehension

Coordination of contact forces during multifinger static prehension.

This study investigated the effects of modifying contact finger forces in one direction-normal or tangential-on the entire set of the contact forces, while statically holding an object. Subjects grasped a handle instrumented with finger force-moment sensors, maintained it at rest in the air, and then slowly: (1) increased the grasping force, (2) tried to spread fingers apart, and (3) tried to s...

Friction Patterns: Local Versus Synergic Effects and Prehension Synergies in the Grasps With Complex

Prehension synergies in the grasps with complex friction patterns: local versus synergic effects and the template control.

We studied adjustments of digit forces to changes in the friction. The subjects held a handle statically in a three-digit grasp. The friction under each digit was either high or low, resulting in eight three-element friction sets (such grasps were coined the grasps with complex friction pattern). The total load was also manipulated. It was found that digit forces were adjusted not only to the s...

Prehension synergies: trial-to-trial variability and principle of superposition during static prehension in three dimensions.

We performed three-dimensional analysis of the conjoint changes of digit forces during prehension (prehension synergies) and tested applicability of the principle of superposition to three-dimensional tasks. Subjects performed 25 trials at statically holding a handle instrumented with six-component force/moment sensors under seven external torque conditions; -0.70, -0.47, -0.23, 0.00, 0.23, 0.4...

Fine Manipulation with Multifinger Hands

We show the existence of two and three finger grasps in the presence of arbitrarily small friction for two and three dimensional smooth objects using a simple new technique. No convexity of the objects is assumed. We also prove the existence of finger gaits for rotating a planar object using three and four fingers. Additional results for smooth convex objects are presented which describe two di...