Bulletin of the Polish Academy of Sciences: Technical Sciences

Abstract

Manipulators mounted on small satellites will be used to perform on-orbit servicing, removal of space debris, and assembly of large orbital structures. During such operations, the manipulator must avoid collisions with the target object or the elements of the assembled structure. Planning of the manipulator trajectory is one of the major challenges for the proposed missions because the motion of the manipulator influences the position and orientation of the satellite. Thus, the dynamic equations of motion must be used during trajectory planning. Methods developed for fixed-base manipulators working on Earth cannot be directly applied. In this paper, we propose a new obstacle vector field (OVF) method for collision-free trajectory planning of a manipulator mounted on a free-floating satellite. The OVF method is based on a vector field that surrounds the obstacles and generates virtual forces that drive the manipulator around the obstacles. The OVF method is compared with the classical artificial potential field (APF) method and the rapidly exploring random trees (RRT) method. In the presented examples the trajectory planning problem is solved for a planar case in which the satellite is equipped with a 2 DoF manipulator. It is shown that the OVF method is more efficient than the APF method, i.e., it allows us to solve the trajectory planning problem in some of the cases, in which the APF method is unsuccessful. The time required to find the solution with the use of the OVF method is shorter than the time needed by the APF and the RRT method.