Coupled-distributed-adaptive-coordinated control for relative orbit and attitude of multiple spacecrafts

According to the consensus theory, the coupled-cooperative control for relative orbits and attitudes of a multi-spacecraft system is investigated under a directed communication topology. Considering the nonlinear equations for the relative orbits of near-earth spacecraft and the attitude motion equations in terms of the modified Rodriguez parameters (MRP), we build six-degrees-of-freedom (6DOF) motion equations with coupled control input and unknown nonlinearities and external disturbance. When the reference state (label of the leader spacecraft) is available only to a partial number of the follower spacecrafts, we develop an adaptive gain control algorithm based on Chebyshev neural networks, which can let a fleet of followers rendezvous at a point with the same attitude. The proposed distributed algorithm for each following spacecraft is only dependent on the information of itself and its neighboring spacecraft. Because the relative velocities and relative angular velocities among the follower spacecrafts are difficult to be measured, we propose a distributed-coupled-adaptive-control algorithm without using neighboring velocities and angular velocities, so that all follower spacecrafts maintain a desired formation and relative attitudes. Simulation results of the formation-flight of six spacecrafts are carried out to study the effectiveness of the proposed control scheme.