Segmented control for retrieval of space debris after captured by Tethered Space Robot

Since the Tethered Space Robot (TSR) has been a research focus as an application of the space tether, a wide range of problems arise in the different phases of the capture mission. In this paper, we propose a new control scheme for the retrieval of passive space debris after captured by a TSR. Under this control scheme, target can be retrieved rapidly, and both of oscillations of tether and target are converged well. First, we derive the equations of attitude motions for the compound system when the passive target satellite is captured by Tethered Space Robot, where the base satellite (chaser) and the space debris (target) are modeled as rigid bodies and the attachment points of the tether are offset from the centers of mass of the two bodies. Then based on the specifics of equations, we divide the retrieval into two phases, and set a threshold for the retrieval. In different phases, different priorities are presented, and different control schemes are given. Finally, the simulation results are shown to prove that the target satellite could be retrieved rapidly and smoothly in a small oscillation, and the oscillation of tether is totally converged at the end of retrieval.