Abstract: Abstract： The problem of relative position control is addressed for spacecraft formation flying around the SunEarth/Moon L2 libration point. In order to avoid the problem of low precision and dependence on accurate model which occurs when controllers are designed according to linearized models, a relative position control technique is proposed that utilizes the framework of the circular restricted threebody problem. Assuming that the leader spacecraft is in a fixed halo orbit, the position of each follower relative to the leader is controlled to approach to a constant via using the active disturbance rejection control method. In this method, the unknown dynamics and external disturbances of the formation flying system are estimated by an extended state observer, which are compensated by a nonlinear state error feedback control law in real time. The numerical simulations show that the relative position errors obtained by the proposed method are all within the demanding range using the thrust from 0.1 μN to 10 mN. Meanwhile, the proposed method has good robustness against unknown disturbances and shows the superiority in control technique.

Key words: Keywords：spacecraft formation flying； leader/follower formation； circular restricted threebody problem； libration point orbits, active disturbance rejection control