Robust adaptive control of relative orbit for nearby spacecraft

The problem of relative orbit motion for nearby spacecrafts is studied in this paper. The relative orbit motion is described in the body frame of a chaser spacecraft. In the case with unknown inertia matrix of the chaser spacecraft, an adaptive control law to make the system globally asymptotically stable is proposed. Under the assumption that the disturbances are unknown yet bounded. Taking the differential acceleration of gravity between two spacecrafts as disturbing acceleration, a robust adaptive law is proposed via modification of the adaptive control law, thus guaranteeing the system to be globally uniformly bounded stable. No orbital parameters are needed in the control law design. Simulation results of a leader-follower spacecraft formation flight and rendezvous are provided to show the effectiveness of proposed control algorithm.