Grasping, coordination and optimal force distribution in multifingered mechanisms

Abstract

SUMMARYIn the field of multifingered mechanisms the control/command problem is mainly a problem o1 coordination. The problem is not only to coordinate joints of a chains but also to coordinate the different chains together.This paper presents a general and efficient method for implementing the control/command of such systems, taking into account the force distribution problem. To solve this problem it is necessary to pay great attention to dynamic effects. To do this, we broke down the Inverse Dynamic Model (I.D.M.) problem into two main levels; One level is devoted to I.D.M. computation; it can be called the Finger Level (F.L.). As we wanted to divide up the work to be done as much as possible, we subdivided the Finger Level according to the number o1 kinematic chains. In addition, we considered a second level, the Coordinator. This level has to control all the chains using the Fingers-to-Object-Interaction Model (F.O.LM.).Next, we will also introduce new grasping systems: Polyvalent Gripper Systems (P.G.S). There are a new solution to multicomponent assembly problems. As they can be equipped with several multifingered mechanisms, they can also use the control/command scheme.

Prehension synergies: Effects of object geometry and prescribed torques

“…This finding refutes an explanation that tangential finger forces are generated by pronation or supination of the forearm, and the fingers serve simply as passive force transmitters (the load is taken by the structural elements of the hand, for instance by the fingertips, without either or both active abduction and adduction efforts of the fingers). Such a mechanism is realized in multifingered robotics hands (Gorce et al 1994;Xiong and Xiong 1997) where normal finger forces are generated by joint actuators while tangential finger forces are resisted passively by hand structure (the finger joints are 1-DoF hinge joints). In human grasping tasks, the fingers are individually controlled (cf.…”

Numerical method applied to object tumbling with multi-body systems

“…The two others (``®nger level'' and``supervisor'') have been developed in more detail respectively in Gorce, Villard and Fontaine (1994) and Rezzoug and Gorce (1997).…”

A cybernetical method for simulating the dynamic erect stance posture control under perturbation

“…Global stability of the human body is controlled using a motor control scheme derived from multi-chain mechanisms coordination (Gorce et al, 1994) or biped robot equilibrium study (Gorce et al, 1995). So, according to these results, we have stated that the equilibrium control of the human body can be decomposed into: a control of the human trunk center of mass acceleration and a control of the forces applied to the trunk by the legs.…”

“…However, using an optimization algorithm, it is possible to find one particular solution which tends to minimize an objective function. Several algorithms have been developed to solve the force distribution problem for multiple-chain systems (Nakamura et al, 1989;Gorce et al, 1994) So, to correct the leg and arm force distribution, we use a minimization of the vertical forces. where:…”