Path planning of free-flying space manipulators: an exact solution for polar robots

Motion planning for free-flying robots can be quite complex due to the fact that any movement of the joints influences the position and the orientation of the spacecraft which carries the manipulator. Several studies have been carried out to plan joint trajectories which eliminate the effects of the dynamic disturbances. Approximate solutions to this problem have been proposed using the concept of the Disturbance Map. The authors have already studied this problem for the case of 2 DOF and 3 DOF planar robots connected with revolute joints developing an exact solution based on the concept of dynamic singularities. Aim of this paper is to extend the proposed methodology to the case of planar polar manipulators, analyzing the peculiarities of these robot arm configurations. A numerical procedure for the evaluation of zero disturbance trajectories is also presented and application examples are developed. The adoption of the proposed strategy improves the performances of spacecraft’s attitude control system.