Space manipulator kinematics for docking operations

Abstract

Robotic manipulators carried by future spacecraft are expected to perform important tasks in space, like satelite assembly. However, since the base of the manipulator (satelite) is not fixed in space, some problems will be encountered. Internal forces and torques applied to the satelite due to the motion of the manipulator will cause changes in the position and attitude of the base. The control method for space manipulators should take into account the motion of the base due to manipulator motions. In this study, the kinematics of a space manipulator system is investigated and a control method based on resolved motion rate control and conservation of angular momentum is developed. It is shown that a manipulator arm follows a prescribed path despite the translations and rotaions of the base. It is also shown that manipulator arm motions can be used to correct the orien- tation of the base. An algorithm is developed assuming that manipula- tor motions cause small rotations in the attitude of the base and the- se rotations are additive. This algorithm is used to find the required motions of the manipulator to rotate the base from an initial orien- tation to a desired final orientation. Results are animated by using a computer graphic simulator program, ROBOSIM.