ON THE KINEMATICS OF MULTIPLE MANIPULATOR SPACE FREE-FLYERS AND THEIRCOMPUTATION

In this article, two basic approaches for kinematics modelling of mult iple manipulator space free-flying robots (SFFRs) are developed. In th e barycentric vector approach, the center of mass of the whole system is taken as a representative point for the translational motion of the system, and a set of body-fixed vectors which reflect both geometric configuration and mass distribution of the system are used. On the oth er hand, the direct path method relies on taking a point on the base b ody (preferably its center of mass) as the representative point for th e translational motion of the system. The consequences of using each o f the two approaches in deriving dynamics equations and in control des ign of SFFRs are discussed. It is revealed that the direct path method is a more appropriate approach for modelling multiple arm systems, in the presence of external forces/torques (i.e., free-flying mode). A 1 4 degree-of-freedom space free-flying system is considered as a benchm ark system and a quantitative comparison between the two approaches is presented. The results show that the direct path method requires sign ificantly less computations for position and velocity analyses. (C) 19 98 John Wiley & Sons, Inc.