Decentralised adaptive output feedback synchronisation tracking control of spacecraft formation flying with time-varying delay

This study deals with the problem of decentralised cooperative position tracking with time-varying delays of interconnect communication in the leader-follower spacecraft formation flight. More specifically, a class of low-pass linear filters is developed to derive a control law without absolute and relative velocity measurement, which is significant for practical applications with low-cost configurations of spacecrafts. Using a well-chosen Lyapunov function, it proves that the proposed control law can make the spacecrafts in formation flying achieve global convergence to the desired position and velocity relevant to the leader, in the face of modelling uncertainties, external disturbances, as well as non-uniform time-varying delays in communication links. Moreover, to release the heavy communication pressures of the leader, a modified control law is designed by introducing a finite-time sliding-mode estimator for a tree-type transformation topology of the formation, in which delays only affect the state (position and velocity) information received from neighbours of each spacecraft. Finally, simulation results are presented to demonstrate the effectiveness of the proposed control schemes.