Closed-loop inverse kinematics algorithms for redundant spacecraft/manipulator systems

This paper is aimed at solving inverse kinematics of space manipulators mounted on a free-floating spacecraft. The approach followed is based on the generalized Jacobian notion that allows to describe the reaction effects of manipulator motion on the spacecraft. Redundancy of the system with respect to the number of task variables for spacecraft attitude and manipulator end-effector pose is considered. Depending on the nature of the task for the spacecraft/manipulator system, a number of closed-loop inverse kinematics algorithms are proposed which are conceptually derived from previously developed algorithms with task space augmentation and task priority strategy for ground-fixed manipulators. In particular, if it is desired to keep spacecraft attitude constant during end-effector task execution, the so-called fixed-attitude-restricted Jacobian is employed. The nice feature of the proposed algorithms is that the transpose of the projected constraint Jacobian is utilized resulting in computationally lighter algorithms than those based on Jacobian pseudoinversion. Case studies are developed for a planar system of a spacecraft with a four-link arm attached.