Analysis of a Redundant Free-Flying Spacecraft/Manipulator System

This paper presents an anlysis based on the momentum conservation equations of a redundant free-flying spacecraft/manipulator system, acting in zero-gravity environment. In order to follow a predefined end-effector path, the inverse kinematics at velocity level is considered. The redundancy i solved alternatively in terms of pseudoinverses and null-space components of the manipulator inertia matrix, the manipulator Jacobian matrix, and the generalized Jacobian matrix. A general manipulation task is defined as end-effector continuous path tracking with simultaneous attitude control of the spacecraft. Three subtasks of the general task are considered: 1) end-effector continuous path tracking with simultaneous attitude maintenance; 2) and 3) changing the attitude of the satellite while keeping fixed position/orientation of the end-effector with respect to either the orbit-fixed coordinate frame or the satellite. The case of manipulator motions that yield no spacecraft attitude disturbance is analyzed in more detail and a special “fixed-attitude-restricted” (FAR) Jacobian is defined. Through singular-value decomposition of this Jacobian, corresponding FAR dexterity measures (FAR manipulability and FAR condition number) are derived.