Dynamics and Stability in Coordination of Multiple Robotic Mechanisms

Abstract

This paper discusses the dynamical coordination of multiple robot manipulators or a multifingered robot hand. The coor dination problem is divided into two phases: determining the resultant force by multiple robotic mechanisms; determining the internal force between mechanisms. The resultant force is used for maintaining dynamic equilibrium and for generat ing the restoring force. A dynamic coordinative control scheme which guarantees the object stability is proposed, associated with the determination of the resultant forces. The internal force is used to satisfy the static frictional constraints and is related to contact stability. The minimizing internal force is defined as the internal force which yields the minimal norm force satisfying static frictional constraints and the minimizing internal force is solved by applying a nonlinear programming method. The concept of the minimizing inter nal force is fundamental and important because it can theo retically answer whether the object can be grasped and ma nipulated with the given finger placement. Contact stability means the ability for the end-effector to maintain contact with an object without slipping when the object is subjected to disturbing external forces. A method of evaluating contact stability is developed. The minimal norm force satisfying the specified degree of contact stability can be obtained by using an algorithm similar to that for the minimizing internal force. Numerical examples of computing the minimizing in ternal forces are given.